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Daily Rules, Proposed Rules, and Notices of the Federal Government

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R2-ES-2011-0053; MO 92210-0-0009]

RIN 1018-AX43

Endangered and Threatened Wildlife and Plants; Designation of Revised Critical Habitat for Southwestern Willow Flycatcher

AGENCY: Fish and Wildlife Service, Interior.
ACTION: Proposed rule.
SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to revise critical habitat for the southwestern willow flycatcher (Empidonax traillii extimus) (flycatcher) under the Endangered Species Act of 1973, as amended (Act). In total, approximately 3,364 km stream kilometers (2,090 stream miles) are being proposed for designation as critical habitat. These areas are being proposed as stream segments, with the lateral extent including the riparian areas and streams that occur within the 100-year floodplain or flood-prone areas. The proposed critical habitat is located on a combination of Federal, State, Tribal, and private lands in Imperial, Inyo, Kern, Los Angeles, Mono, Orange, Riverside, Santa Barbara, San Bernardino, San Diego, and Ventura Counties in California; Clark, Lincoln, and Nye Counties in southern Nevada; Kane, San Juan, and Washington Counties in southern Utah; Alamosa, Conejos, Costilla, La Plata, and Rio Grande Counties in southern Colorado; Apache, Cochise, Gila, Graham, Greenlee, La Paz, Maricopa, Mohave, Pima, Pinal, Santa Cruz, Yavapai, and Yuma Counties in Arizona; and Catron, Cibola, Dona Ana, Grant, Hidalgo, McKinley, Mora, Rio Arriba, Santa Fe, San Juan, Sierra, Soccoro, Taos, and Valencia Counties in New Mexico.
DATES: We will accept comments received or postmarked on or before October 14, 2011. We must receive requests for public hearings, in writing, at the address shown in theFOR FURTHER INFORMATION CONTACTsection by September 29, 2011.
ADDRESSES: (1)Electronically:Go to the Federal eRulemaking Portal:http://www.regulations.gov.In the Enter Keyword or ID box, enter Docket No. FWS-R2-ES-2011-0053, which is the docket number for this rulemaking.

(2)By hard copy:Submit by U.S. mail or hand-delivery to: Public Comments Processing, Attn: FWS-R2-ES-2011-053; Division of Policy and Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive, MS 2042-PDM; Arlington, VA 22203.

We will not accept e-mail or faxes. We will post all comments onhttp://www.regulations.gov.This generally means that we will post any personal information you provide us (see the Public Comments section below for more information).

FOR FURTHER INFORMATION CONTACT: Steve Spangle, Field Supervisor, U.S. Fish and Wildlife Service, Arizona Ecological Services Office, 2321 West Royal Palm Rd., Suite 103, Phoenix, AZ 85021; telephone 602-242-0210; facsimile 602-242-2513. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:

Public Comments

We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other concerned government agencies, the scientific community, industry, or any other interested party concerning this proposed rule. We particularly seek comments concerning:

(1) The reasons why we should or should not designate habitat as “critical habitat” under section 4 of the Act (16 U.S.C. 1531et seq.), including whether there are threats to the species from human activity, the degree of which can be expected to increase due to the designation, and whether that increase in threat outweighs the benefit of designation such that the designation of critical habitat may not be prudent.

(2) Specific information on:

(a) The amount and distribution of southwestern willow flycatcher habitat;

(b) What areas that were occupied at the time of listing that contain features essential to the conservation of the species should be included in the designation and why;

(c) What areas not occupied at the time of listing that meet our criteria for being essential to the conservation of the species should be included in the designation and why;

(d) Special management considerations or protection that may be needed for the physical or biological features essential to the conservation of the species in the critical habitat areas we are proposing, including managing for the potential effects of climate change;

(e) Stream segments, many of which are highlighted in the Southwestern Willow Flycatcher Recovery Plan (Recovery Plan) (Service 2002) and included in this proposed rule, that are not now known to have flycatcher nesting territories or known to only have few nesting flycatchers that may be capable of being improved for flycatcher recovery purposes. We specifically seek information about streams within the Amargosa, Salton, Mohave, Powell, San Juan, Santa Cruz, and Hassayampa and Agua Fria Management Units. Please provide information on flycatcher distribution and abundance, habitat quality, habitat locations, habitat improvement projects, management actions needed to improve habitat, habitat quality limitations, habitat recovery potential, and any other flycatcher or flycatcher-habitat-specific information, and;

(f) Flycatcher habitat suitability in specific areas within the Santa Ana and San Diego Management Units in southern California. Please provide information on flycatcher habitat suitability for recovery at the following areas: (1) Entirety of Temescal Wash including Alberhill Creek in Riverside County; (2) entirety of Murrieta Creek in Riverside County; (3) Potrero Creek near the city of Beaumont in Riverside County; (4) Cajon Creek from Lone Pine Canyon to California State Highway 138 in San Bernardino County; and (5) Tijuana River from Dairy Mart Road to the Tijuana River Estuary in San Diego County.

(3) Land use designations and current or planned activities in the subject areas and their possible impacts on proposed critical habitat.

(4) Information on the projected and reasonably likely impacts of climate change on the flycatcher, the features essential to its conservation and the areas proposed as critical habitat.

(5) Any probable economic, national security, environmental, cultural, or other relevant impacts of designating any area that may be included in the final designation; in particular, any impacts on small entities, and the benefits of including or excluding areas that exhibit these impacts.

(6) Whether any specific areas we are proposing for critical habitat designation should be considered for exclusion under section 4(b)(2) of the Act, and whether the benefits of potentially excluding any specific area outweigh the benefits of including that area under section 4(b)(2) of the Act, in particular.

(a) For specific lands that we should consider for exclusion under section 4(b)(2) of the Act, please provide us management plans, conservation easements, agreements, Habitat Conservation Plans (HCP), or other appropriate information, which describe the commitment and assurances of protection of the physical or biological features of flycatcher critical habitat; property boundaries; flycatcher status, distribution, and abundance; and management actions to protect the physical or biological features of flycatcher habitat.

(b) For lands we evaluated and excluded from critical habitat under section 4(b)(2) of the Act during the 2005 flycatcher critical habitat designation and those who wish to seek exclusion for this re-designation, please resubmit your request. In addition to your request, please include any updated information that pertains to the commitment and assurances of protection of flycatcher habitat; the physical or biological features of flycatcher critical habitat; property boundaries; flycatcher status, distribution, and abundance; and management actions to protect the physical or biological features of flycatcher habitat. Include the specific results of implementing these management plans since our 2005 flycatcher critical habitat designation.

(c) Information concerning the benefits of excluding or retaining lands we identify in this proposed critical habitat rule under consideration for exclusion under section 4(b)(2) of the Act. We specifically seek information about the possible exclusion of Elephant Butte Reservoir; areas within the operating pool of the reservoir may be subject to exclusion under 4(b)(2) of the Act if we determine that the benefits of excluding the area due to potential impacts to water operations outweigh the benefits to the subspecies of including the area as critical habitat.

(7) Whether we could improve or modify our approach to designating critical habitat in any way to provide for greater public participation and understanding, or to better accommodate public concerns and comments.

You may submit your comments and materials concerning this proposed rule by one of the methods listed in theADDRESSESsection. We will not accept comments sent by e-mail or fax or to an address not listed in theADDRESSESsection. We will post your entire comment—including your personal identifying information—onhttp://www.regulations.gov.You may request at the top of your document that we withhold personal information such as your street address, phone number, or e-mail address from public review; however, we cannot guarantee that we will be able to do so.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection onhttp://www.regulations.gov,or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Arizona Ecological Services Office in Phoenix, Arizona (seeFOR FURTHER INFORMATION CONTACT).

Background

It is our intent to include only those topics directly relevant to the designation of critical habitat for the southwestern willow flycatcher (flycatcher) in this proposed rule. Background information on the flycatcher can be found in the final flycatcher critical habitat rule published in theFederal Registeron October 19, 2005 (70 FR 60886); our October 12, 2004, proposed critical habitat rule (69 FR 60706); the Southwestern Willow Flycatcher Recovery Plan (Recovery Plan) (Service 2002); our first flycatcher critical habitat designation, published July 22, 1997 (62 FR 39129), and August 20, 1997 (62 FR 44228); the final flycatcher listing rule (60 FR 10694; February 27, 1995); the 10-year flycatcher study in central Arizona (Paxtonet al.2007a); the 2007 rangewide status report (Durstet al.2008); and flycatcher survey protocol and natural history summary (Soggeet al.2010). Other reports can be retrieved from the U.S. Geological Survey's (USGS) flycatcher site athttp://sbsc.wr.usgs.gov/cprs/research/projects/swwf.The current 2005 critical habitat rule remains in effect while this rulemaking process proceeds.

The flycatcher is a small, insect-eating, neotropical migrant bird, from the taxonomic order Passeriformes. It grows to about 15 centimeters (5.8 inches) in length. The flycatcher is one of four subspecies of the willow flycatcher currently recognized (Hubbard 1987, pp. 3-6; Unitt 1987, pp. 137-144), although Browning (1993, p. 248) suggests a possible fifth subspecies (Empidonax traillii campestris) in the central and midwestern United States. As an insect-eating generalist (Service 2002, p. 26), the flycatcher eats a wide range of invertebrate prey including flying, and ground- and vegetation-dwelling, insect species of terrestrial and aquatic origins (Drostet al.2003, pp. 96-102). The flycatcher spends the winter in locations such as southern Mexico, Central America, and probably South America (Ridgely and Gwynne 1989, p. 303; Stiles and Skutch 1989, pp. 321-322; Howell and Webb 1995, pp. 496-497; Unitt 1997, pp. 70-73; Koronkiewiczet al.1998, p. 12; Unitt 1999, p. 14).

All willow flycatcher subspecies spend time migrating and breeding in the United States from April to September. Use of riparian habitats along major drainages in the Southwest during migration has been documented (Soggeet al.1997, pp. 3-4; Yong and Finch 1997, p. 253; Johnson and O'Brien 1998, p. 2; McKernan and Braden 1999, p. 17; Koronkiewiczet al.2004, pp. 9-11). Many of the willow flycatchers found migrating are detected in riparian habitats or patches (small areas of riparian vegetation) that would be unsuitable for nest placement (the vegetation structure is too short or sparse, or the patch of vegetation is too small). In these drainages migrating flycatchers may use a variety of riparian habitats, including ones dominated by native or exotic plant species, or mixtures of both (Service 2002, p. E-3). Willow flycatchers, like most small, migratory, insect-eating birds, require food-rich stopover areas in order to replenish energy reserves and continue their northward or southward migration (Finchet al.2000, pp. 71, 78, and 79; Service 2002, pp. E-3 and 42). Migration stopover areas are likely critically important for flycatcher productivity and survival (Soggeet al.1997, p. 13; Yong and Finch 1997, p. 253; Service 2002, pp. E-3,19).

The historical breeding range of the flycatcher includes southern California, southern Nevada, southern Utah, Arizona, New Mexico, western Texas, southwestern Colorado, and extreme northwestern Mexico. The flycatcher's current range is similar to the historical range, but the quantity of suitable habitat within that range is reduced from historical levels (Service 2002, pp. 7-10).

The known geographical area historically occupied by this flycatcher subspecies was once larger (Service 2002, pp. 7-10). Historical records described nesting birds in southern California, Nevada, Utah; Arizona and New Mexico; western Texas; southwestern Colorado; and extreme northwestern Mexico (Hubbard 1987, pp. 6-10; Unitt 1987, pp. 144-152; Browning 1993, pp. 248, 250). At the time of listing in February 1995 (60 FR 10694), the distribution and abundance of nesting flycatchers, their natural history, and areas occupied by nonbreeding, migrating, and dispersing flycatchers were not well known. In February 1995, 359 territories wereknown only from California, Arizona, and New Mexico. Unitt (1987, p. 156) estimated the entire population was, “well under 1,000 pairs, more likely 500,” and 230 to 500 territories were estimated to exist in the July 23, 1993, flycatcher listing proposal (58 FR 39495, p. 39498).

At the time of listing, breeding sites in California, Nevada, Utah, and Colorado described by Unitt (1987, pp. 149-152) were adopted as the subspecies' northern boundary. However, the collection and analysis of genetic material across this part of the bird's range has since refined this boundary (Paxton 2000, pp. 3, 18-20), and reduced the extent of the northern boundary of this southwestern subspecies in Utah and Colorado (Service 2002, Figure 3). Territories once believed to be held by southwestern willow flycatchers in Utah and Colorado are now more accurately known to be occupied by a different, non-listed willow flycatcher subspecies. As a result, the southwestern subspecies' range only occurs in the southernmost portions of Utah and Colorado. This genetic work also confirmed the identity of southwestern willow flycatcher subspecies throughout the rest of its range.

The USGS has continued to collect genetic information to help refine the northern boundary of the subspecies' range in Utah, Colorado, and New Mexico (Paxtonet al.2007b). They reconfirmed the genetic markers that identify differences among flycatcher subspecies, with breeding sites clustering into two groups separated approximately along the currently recognized boundary; however, they noted a distinct genetic boundary line between the subspecies does not exist (Paxtonet al.2007b, p. 17). Instead of a distinct boundary, they suggested that the boundary should be thought of as a “region of genetic overlap” (Paxtonet al.2007b, p. 17). They also described that this genetic overlap region will likely widen and contract over time based upon habitat changes (Paxtonet al.2007b, p. 17). An additional complication in refining the subspecies' northern boundary is that this region is sparsely populated with breeding flycatchers, and therefore only minimal information is available that would help narrow down the location of a boundary (Paxtonet al.2007b, p. 16). We continue to seek out territories and collect genetic samples to further our understanding of this area, but we currently recognize the northern geographic boundary of the flycatcher as described in the Recovery Plan (Service 2002, Figures 3, 4).

The flycatcher currently breeds in areas from near sea level to over 2,600 meters (m) (8,500 feet [ft]) (Durstet al.2008, p. 14) in vegetation alongside rivers, streams, or other wetlands (riparian habitat). It establishes nesting territories, builds nests, and forages where mosaics of relatively dense and expansive growths of trees and shrubs are established, near or adjacent to surface water or underlain by saturated soil (Soggeet al.2010, p. 4). Habitat characteristics such as dominant plant species, size and shape of habitat patch, tree canopy structure, vegetation height, and vegetation density vary widely among breeding sites. Nests are typically placed in trees where the plant growth is most dense, where trees and shrubs have vegetation near ground level, and where there is a low-density canopy. Some of the more common tree and shrub species currently known to comprise nesting habitat include Goodings willow (Salix gooddingii), coyote willow (Salix exigua), Geyers willow (Salix geyerana), arroyo willow (Salix lasiolepis), red willow (Salix laevigata), yewleaf willow (Salix taxifolia), boxelder (Acer negundo), tamarisk (also known as saltcedar,Tamarix ramosissima), and Russian olive (Eleagnus angustifolia) (Service 2002, p. D-2). While there are exceptions, generally flycatchers are not found nesting in areas without willows, tamarisk, or both.

A breeding site is simply an area along the river that has been described while surveying for flycatcher territories (Service 2002, p. C-4; Soggeet al.2010, p. 34). A breeding site can contain none, only one, or many territories. However, within this proposed rule, we refer to breeding sites as areas where flycatcher territories were detected. A territory is defined as a discrete area defended by a resident single flycatcher or pair of flycatchers within a single breeding season (Soggeet al.2010, p. 34). This is usually evidenced by the presence of a singing male, and possibly one or more mates (Soggeet al.2010, p. 34).

At the end of 2007, 1,299 flycatcher breeding territories were estimated to occur throughout southern California, southern Nevada, southern Utah, southern Colorado, Arizona, and New Mexico (Durstet al.2008, p. 4). Some of the flycatcher breeding sites having the highest number of territories are found along the middle Rio Grande and upper Gila River in New Mexico, and Roosevelt Lake and the San Pedro and Gila River confluence area in central Arizona.

Flycatchers are believed to exist and interact as groups of metapopulations (Service 2002, p. 72). A metapopulation is a group of geographically separate flycatcher breeding populations connected to each other by immigration and emigration (Service 2002, p. 72). Flycatcher populations are most stable where many connected sites or large populations exist (Service 2002, p. 72). Metapopulation persistence or stability is more likely to improve by adding more breeding sites than with the addition of territories to existing sites (Service 2002, p. 72). This would distribute birds across a greater geographical range, minimize risk of simultaneous catastrophic population loss, and avoid genetic isolation (Service 2002, p. 72).

Flycatchers have higher site fidelity (to a local area) than nest fidelity (to a specific nest location) and can move among sites within stream drainages and between drainages (Kenwood and Paxton 2001, pp. 29-31). Within-drainage movements are more common than between-drainage movements (Kenwood and Paxton 2001, p. 18). Juvenile flycatchers were the group of flycatchers that moved (dispersed) the farthest to new and distant breeding sites from the area where they hatched (Paxtonet al.2007a, p. 74). The USGS's 10-year flycatcher study in central Arizona (Paxtonet al.2007a) is the key movement study that has generated these conclusions, augmented by other flycatcher banding and re-sighting studies (Sedgwick 2004, p. 1103; McLeodet al.2008, p. 110).

The difference in flycatcher dispersal distance among different study areas and regions reflects the varying spatial arrangement of breeding habitat, illustrating how dispersal tendencies are influenced by the geographic distribution of habitat at the stream segment, drainage, and landscape scales (Paxtonet al.2007a, p. 75). While USGS' study focused its effort in central Arizona at two of the largest breeding sites, it also included multiple auxiliary sites (up to 444 km or 275 mi away), along with other researchers and surveyors across the flycatcher's range paying attention to whether flycatchers were banded or not. As a result, the broad scope of the study of flycatcher movement extends broadly beyond a localized, regional area, where habitat configuration dominates the results.

Banded flycatchers from season-to-season (and sometimes within season) were recorded moving from 50 m (150 feet) to 444 km (275 mi) to try and nest. Some long-distance season-to-season movement records captured flycatchers moving from the Basin and Mohave Recovery Unit to the Lower Colorado Recovery Unit and from the LowerColorado Recovery Unit to the Gila Recovery Unit.

The USGS assimilated all of the flycatcher movement information and concluded that rapid colonization and increased metapopulation stability could be accomplished by establishing breeding sites within 30 to 40 km (18 to 25 mi) of each other (Paxtonet al.2007a, p. 4). Flycatchers at breeding sites configured in this way would be able to regularly disperse to new breeding sites or move between known breeding sites within the same year or from year-to-year. This proximity of sites would increase the connectivity and stability of the metapopulation and smaller, more distant breeding sites.

Because the breeding range of the flycatcher encompasses a broad geographic area with much site variation, management of recovery is approached in the Recovery Plan by dividing the flycatcher's range into 6 Recovery Units, each of which are further subdivided into 4 to 7 Management Units (for a total of 32 Management Units) (Service, pp. 61-63). This provides an organizational strategy to “characterize flycatcher populations, structure recovery goals, and facilitate effective recovery actions that should closely parallel the physical, biological, and logistical realities on the ground” (Service 2002, p. 61). Recovery goals are recommended for 29 of the 32 Management Units (see Methodology Overview section). Recovery Units are defined based on large watershed and hydrologic units. Within each Recovery Unit, Management Units are based on watershed or major drainage boundaries at the Hydrologic Unit Code Cataloging Unit level (standard watershed boundaries which have already been defined for other purposes). The “outer” boundaries of some Recovery Units and Management Units were defined by the flycatcher's range boundaries. This proposed designation of critical habitat is organized geographically within these Recovery Units and Management Units (see “Methodology Overview” section below).

The Recovery Plan (Service 2002) provides reasonable actions recommended to recover the flycatcher and provides two criteria, either of which can be met, in order to consider downlisting the species to threatened (Service 2002, pp. 77-78). The first alternative for downlisting requires reaching a total population of 1,500 flycatcher territories geographically distributed among all Recovery Units and maintained for 3 years with habitat protections (Service 2002, pp. 77-78). Habitat protections include a variety of options such as HCPs, conservation easements, or safe harbor agreements. The second alternative approach for downlisting calls for reaching a population of 1,950 territories also strategically distributed among all Recovery and Management Units for 5 years without additional habitat protection (Service 2002, pp. 77-78).

In order to delist this flycatcher subspecies (to remove it from the List of Endangered and Threatened Wildlife and Plants), the Recovery Plan recommends that a minimum of 1,950 territories are geographically distributed among all Recovery and Management Units, and that twice the amount of habitat is provided to maintain these territories over time. Second, these habitats must be protected from threats to assure maintenance of these populations and habitat for the foreseeable future through development and implementation of conservation management agreements (Service 2002, pp. 79-80). Third, all of these delisting criteria must be accomplished and their effectiveness demonstrated for a period of 5 years (Service 2002, pp. 79-80). This critical habitat proposal is structured to allow the Service to work toward achieving the numerical, geographical, and habitat-related recovery goals.

Twice the amount of suitable habitat is needed to support the numerical territory goals, because the long-term persistence of flycatcher populations cannot be assured by protecting only those habitats in which flycatchers currently breed (Service 2002, p. 80). It is important to recognize that most flycatcher breeding habitats are susceptible to future changes in site hydrology (natural or human-related), human impacts such as development or fire, and natural catastrophic events such as flood or drought (Service 2002, p. 80). Furthermore, as the vegetation at sites matures, it can lose the structural characteristics that make it suitable for breeding flycatchers (Service 2002, p. 80). These and other factors can destroy or degrade breeding sites, such that one cannot expect any given breeding site to remain suitable in perpetuity (Service 2002, p. 80). Thus, it is necessary to have additional suitable habitat available to which flycatchers, displaced by such habitat loss or change, can readily move (Service 2002, p. 80).

Previous Federal Actions

The flycatcher was listed as endangered on February 27, 1995 (60 FR 10694). On July 22, 1997, we published a final critical habitat designation for the flycatcher along 964 river km (599 river mi) in Arizona, California, and New Mexico (62 FR 39129). We published a correction notice on August 20, 1997, on the lateral extent of critical habitat (62 FR 44228).

As a result of a 1998 lawsuit from the New Mexico Cattlegrower's Association, on October 19, 2005 (70 FR 60886), we published a revised final flycatcher critical habitat rule for portions of Arizona, California, New Mexico, Nevada, and Utah, totaling approximately 48,896 ha (120,824 ac) or 1,186 km (737 mi). River segments were designated as critical habitat in 15 of the 32 Management Units described in the Recovery Plan (Service 2002, p. 63).

We were sued by the Center for Biological Diversity over our 2005 critical habitat rule, and on July 13, 2010, we agreed to redesignate critical habitat. The resulting settlement left the existing critical habitat designation from 2005 in effect, and required that we deliver a proposed rule for new revised critical habitat to theFederal Registerby July 31, 2011, and a final rule by July 31, 2012.

Critical Habitat Background

Critical habitat is defined in section 3 of the Act as:

(1) The specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the Act, on which are found those physical or biological features:

(a) Essential to the conservation of the species; and

(b) Which may require special management considerations or protection; and

(2) Specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.

Conservation, as defined under section 3 of the Act, means to use and the use of all methods and procedures that are necessary to bring an endangered or threatened species to the point at which the measures provided under the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transplantation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking.

Critical habitat receives protection under section 7 of the Act through therequirement that Federal agencies ensure, in consultation with the Service, that any action they authorize, fund, or carry out is not likely to result in the destruction or adverse modification of critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation does not allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by non-Federal landowners. Where a landowner seeks or requests Federal agency funding or authorization for an action that may affect a listed species or critical habitat, the consultation requirements of section 7(a)(2) would apply, but even in the event of a destruction or adverse modification finding, the obligation of the Federal action agency and the landowner is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.

For inclusion in a critical habitat designation, the habitat within the geographical area occupied by the species at the time it was listed must contain physical or biological features which are essential to the conservation of the species and which may require special management considerations or protection. Critical habitat designations identify, to the extent known using the best scientific and commercial data available, those physical or biological features that are essential to the conservation of the species (such as space, food, cover, and protected habitat), focusing on the principal biological or physical constituent elements (primary constituent elements) within an area that are essential to the conservation of the species (such as roost sites, nesting grounds, seasonal wetlands, water quality, tide, soil type). Primary constituent elements are the elements of physical or biological features that, when laid out in the appropriate quantity and spatial arrangement to provide for a species' life-history processes, are essential to the conservation of the species.

Under the Act, we can designate critical habitat in areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species. We designate critical habitat in areas outside the geographical area occupied by a species only when a designation limited to its range would be inadequate to ensure the conservation of the species. When the best available scientific data do not demonstrate that the conservation needs of the species require such additional areas, we will not designate critical habitat in areas outside the geographical area occupied by the species. An area currently occupied by the species but that was not occupied at the time of listing may, however, be essential to the conservation of the species and may be included in the critical habitat designation.

Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific and commercial data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in theFederal Registeron July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658)), and our associated Information Quality Guidelines, provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.

When we determine which areas should be designated as critical habitat, our primary source of information is generally the information developed during the listing process for the species. Additional information sources may include the recovery plan for the species, articles in peer-reviewed journals, conservation plans developed by States and counties, scientific status surveys and studies, biological assessments, or other unpublished materials and expert opinion or personal knowledge.

We recognize that critical habitat designated at a particular point in time may not include all of the habitat areas that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be required for recovery of the species. Areas that are important to the conservation of the species, both inside and outside the critical habitat designation, will continue to be subject to: (1) Conservation actions implemented under section 7(a)(1) of the Act, (2) regulatory protections afforded by the requirement in section 7(a)(2) of the Act for Federal agencies to insure their actions are not likely to jeopardize the continued existence of any endangered or threatened species, and (3) the prohibitions of section 9 of the Act if actions occurring in these areas may affect the species. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. These protections and conservation tools will continue to contribute to recovery of this species. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, HCPs, or other species conservation planning efforts if new information available at the time of these planning efforts calls for a different outcome.

Physical or Biological Features

In accordance with sections 3(5)(A)(i) and 4(b)(1)(A) of the Act and regulations at 50 CFR 424.12, in determining which areas within the geographical area occupied by the species (in this case a subspecies) at the time of listing to designate as critical habitat, we consider the physical or biological features essential to the conservation of the flycatcher and which may require special management considerations or protection. These include, but are not limited to:

(1) Space for individual and population growth and for normal behavior;

(2) Food, water, air, light, minerals, or other nutritional or physiological requirements;

(3) Cover or shelter;

(4) Sites for breeding, reproduction, or rearing (or development) of offspring; and

(5) Habitats that are protected from disturbance or are representative of the historical, geographical, and ecological distributions of a species.

We derive the specific physical or biological features required for the flycatcher from studies of this subspecies' habitat, ecology, and life history as described below. The most comprehensive, current, and thorough documents are the Recovery Plan (Service 2002, Appendix D), Survey Protocol and Natural History Summary (Soggeet al.2010), and 10-year central Arizona ecology study (Paxtonet al.2007a).

In general, the areas proposed for designation as critical habitat are designed to provide sufficient riparian habitat for breeding, non-breeding, territorial, dispersing, and migrating flycatchers in order to reach thegeographic distribution, abundance, and habitat-related recovery goals described in the Recovery Plan (Service 2002, pp. 77-85). We are not proposing any areas as critical habitat solely because they serve as a migration habitat. Instead, the areas we are proposing serve a variety of functions, including habitat to be used by migrating flycatchers. The habitat components important for conservation of this subspecies were determined from studies of flycatcher behavior and habitat use throughout the bird's range (see Background section).

In general, the physical or biological features of critical habitat for nesting flycatchers are found in the riparian areas within the 100-year floodplain or flood-prone area. Flycatchers use riparian habitat for feeding, sheltering, and cover while breeding, migrating, and dispersing. It is important to recognize that flycatcher habitat is ephemeral in its presence, and its distribution is dynamic in nature because riparian vegetation is prone to periodic disturbance (such as flooding) (Service 2002, p. 17). Even with the dynamic shifts in habitat conditions, one or more of the primary constituent elements described below are found throughout each of the units that we are proposing as critical habitat.

Flycatcher habitat may become unsuitable for breeding through maturation or disturbance of the riparian vegetation, but it may remain suitable for use during migration or for foraging. This situation may be only temporary, and vegetation may cycle back into suitability as breeding habitat (Service 2002, p. 17). Therefore, it is not practical to assume that any given breeding habitat area will remain suitable over the long term or persist in the same location (Service 2002, p. 17). Over a 5-year period, flycatcher habitat can, in optimum conditions, germinate, be used for migration or foraging, continue to grow, and eventually be used for nesting. Thus, flycatcher habitat that is not currently suitable for nesting at a specific time, but is useful for foraging and migration, can still be important for flycatcher conservation. Feeding sites and migration stopover areas are important components for the flycatcher's survival, productivity, and health, and they can also be areas where new breeding habitat develops as nesting sites are lost or degraded (Service 2002, p. 42). These successional cycles of habitat change are important for long-term persistence of flycatcher habitat.

Based on our current knowledge of the life history and ecology of the flycatcher and the relationship of its life-history functions to its habitat, as summarized in the “Background” section above and in more detail in the Recovery Plan (Service 2002, Chapter II), it is important to recognize the interconnected nature of the physical or biological features that provide the primary constituent elements of critical habitat. Specifically, we consider the relationships between river function, hydrology, floodplains, aquifers, and plant growth, which form the environment essential to the conservation of the flycatcher.

The hydrologic regime (stream flow pattern) and supply of (and interaction between) surface and subsurface water is a driving factor in the long-term maintenance, growth, recycling, and regeneration of flycatcher habitat (Service 2002, p. 16). As streams reach the lowlands, their gradients typically flatten and surrounding terrain opens into broader floodplains (Service 2002, p. 32). In these geographic settings, the stream-flow patterns (frequency, magnitude, duration, and timing) will provide the necessary stream-channel conditions (wide configuration, high sediment deposition, periodic inundation, recharged aquifers, lateral channel movement, and elevated groundwater tables throughout the floodplain) that result in the development of flycatcher habitat (Poffet al.1997, pp. 770-772; Service 2002, p. 16). Allowing the river to flow over the width of the floodplain, when overbank flooding occurs, is integral to allow deposition of fine moist soils, water, nutrients, and seeds that provide the essential material for plant germination and growth. An abundance and distribution of fine sediments extending farther laterally across the floodplain and deeper underneath the surface retains much more subsurface water, which in turn supplies water for the development of the vegetation that provides flycatcher habitat and micro-habitat conditions (Service 2002, p. 16). The interconnected interaction between groundwater and surface water contributes to the quality of riparian vegetation community (structure and plant species) and will influence the germination, density, vigor, composition, and the ability of vegetation to regenerate and maintain itself (Arizona Department of Water Resources 1994, pp. 31-32).

In many instances, flycatcher breeding sites occur along streams where human impacts are minimized enough to allow more natural processes to create, recycle, and maintain flycatcher habitat. However, there are also breeding sites that are supported by various types of supplemental water including agricultural and urban run-off, treated water outflow, irrigation or diversion ditches, reservoirs, and dam outflows (Service 2002, p. D-15). Although the waters provided to these habitats might be considered “artificial,” they are often important for maintaining the habitat in appropriate condition for breeding flycatchers within the existing environment.

In considering the specific physical or biological features essential for the conservation of the flycatcher, it is also important to consider longer-term processes that may influence habitat changes over time, such as climate change. Climate change is a long-term shift in the statistics of the weather (including its averages). In itsFourth Assessment Report,the Intergovernmental Panel on Climate Change (IPCC) defines climate change as, “a change in the state of the climate that can be identified by changes in the mean and/or variability of its properties and that persists for an extended period, typically decades or longer” (Solomonet al.2007, p. 943). Changes in climate already are occurring. Examples of observed changes in the physical environment include an increase in global average sea level and declines in mountain glaciers and average snow cover in both the northern and southern hemispheres (IPCC 2007a, p. 30). At continental, regional and ocean basin scales, observed changes in long-term trends of other aspects of climate include: A substantial increase in precipitation in eastern parts of North American and South America, northern Europe, and northern and central Asia; declines in precipitation in the Mediterranean, southern Africa, and parts of southern Asia; and an increase in intense tropical cyclone activity in the North Atlantic since about 1970 (IPCC 2007a, p. 30).

Projections of climate change globally and for broad regions through the 21st century are based on the results of modeling efforts using state-of-the-art Atmosphere-Ocean General Circulation Models and various greenhouse gas emissions scenarios (Meehlet al.2007, p. 753; Randallet al.2007, pp. 596-599). As is the case with all models, there is uncertainty associated with projections due to assumptions used and other features of the models. However, despite differences in assumptions and other parameters used in climate change models, the overall surface air temperature trajectory is one of increased warming in comparison to current conditions (Meehlet al.2007, p. 762; Prinnet al.2011, p. 527). Among the IPCC's projections for the 21st century are the following: (1) It is virtually certain there will be warmerand more frequent hot days and nights over most of the earth's land areas; (2) it is very likely there will be increased frequency of warm spells and heat waves over most land areas, and the frequency of heavy precipitation events will increase over most areas; and (3) it is likely that increases will occur in the incidence of extreme high sea level (excludes tsunamis), intense tropical cyclone activity, and the area affected by droughts in various regions of the world (IPCC 2007b, p. 8).

Changes in climate can have a variety of direct and indirect ecological impacts on species, and can exacerbate the effects of other threats. Climate-associated environmental changes to the landscape, such as decreased stream flows, increased water temperatures, reduced snowpack, and increased fire frequency, affect species and their habitats. The vulnerability of a species to climate change impacts is a function of the species' sensitivity to those changes, its exposure to those changes, and its capacity to adapt to those changes. The best available science is used to evaluate the species' response to these stressors. We recognize that future climate change may present a particular challenge evaluating habitat conditions for species like the flycatcher because the additional stressors may push species beyond their ability to survive in their present location.

Exactly how climate change will affect precipitation in the specific areas with flycatcher habitat is uncertain. However, consistent with recent observations of regional effects of climate change, the projections presented for the Southwest predict warmer, drier, and more drought-like conditions (Hoerling and Eischeid 2007, p. 19; Seageret al.2007, p. 1181). For example, climate simulations of the Palmer Drought Severity Index (PSDI) (a calculation of the cumulative effects of precipitation and temperature on surface moisture balance) for the Southwest for the periods of 2006 to 2030 and 2035 to 2060 show an increase in drought severity with surface warming. Additionally, drought still increases even during wetter simulations because of the effect of heat-related moisture loss through evaporation and evapotranspiration (Hoerling and Eischeid 2007, p. 19). Annual mean precipitation is likely to decrease in the Southwest, as is the length of snow season and snow depth (IPCC 2007b, p. 887). Most models project a widespread decrease in snow depth in the Rocky Mountains and earlier snowmelt (IPCC 2007b, p. 891). In summary, we expect that climate change will result in a warmer, drier climate, and reduced surface water across the flycatcher's range.

In the recent past, drought has had both negative and positive effects on breeding flycatchers and their habitat, which can provide insight into how climate change may affect flycatchers and flycatcher habitat. For example, the extreme drought of 2002 caused near complete reproductive failure of the 146 flycatcher territories at Roosevelt Lake in central Arizona (Smithet al.2003, pp. 8, 10), and caused a dramatic rise in the prevalence of non-breeding and unpaired flycatchers (Paxtonet al.2007a, p. 4). While extreme drought during a single year can generate impacts to breeding success, drought can also have localized short-term benefits in some regulated environments. For instance, at some reservoirs (such as Roosevelt Lake, Arizona, and Lake Isabella, California), drought led to reduced water storage, which increased the exposure of wet soils at the lake's perimeter. Continued drought in those areas allowed the exposed areas to grow vegetation and become new flycatcher nesting habitat (Elliset al.2008, p. 44). These short-term and localized habitat increases are not likely sustainable with persistent drought or long-term predictions of a drier environment, because of the overall importance of the presence of surface water and elevated groundwater needed to grow dense riparian forests for flycatcher habitat. As a result, we expect long-term climate trends associated with a drier climate to have an overall negative effect on the available rangewide habitat for flycatchers.

Considering these issues and other information regarding the biology and ecology of the species, we have determined that the flycatcher requires the essential physical or biological features described below.

Space for Individual and Population Growth and for Normal Behavior

Streams of lower gradient and more open valleys with a wide and broad floodplain are the geological settings that are known to support flycatcher breeding habitat from near sea level to about 2,600 m (8,500 ft) in elevation in southern California, southern Nevada, southern Utah, southern Colorado, Arizona, and New Mexico (Service 2002, p. 7). Lands with moist conditions that support riparian plant communities are areas that provide flycatcher habitat. Conditions like these typically develop in lower elevation floodplains as well as where streams enter impoundments, either natural (such as beaver ponds) or human-made (reservoirs). Low-gradient stream conditions may also occur at high elevations, as in the marshy mountain meadows supporting flycatchers in the headwaters of the Little Colorado River near Greer, Arizona, or the flat-gradient portions of the upper Rio Grande in south-central Colorado and northern New Mexico (Service 2002, p. 32). Sometimes, the low-gradient wider floodplain exists only at the habitat patch itself within a stream that is otherwise steeper in gradient (Service 2002, p. D-12).

Relatively steep, confined streams can also support flycatcher breeding habitat (Service 2002, p. D-13). For instance, a portion of the San Luis Rey River in California supports a substantial flycatcher population and stands out among flycatcher habitats as having a relatively high gradient and being confined in a fairly narrow, steep-sided valley (Service 2002, p. D-13). Even a steep, confined canyon or mountain stream may present local conditions where just a small area less than a hectare (acre) in size of flycatcher breeding habitat may develop (Service 2002, p. D-13). Such sites are important individually and in aggregate to contribute to metapopulation stability, site connectivity, and gene flow (Service 2002, p. D-13). Flycatchers can occupy very small, isolated habitat patches and may occur in fairly high densities within those small patches.

Many willow flycatchers are found along streams using riparian habitat during migration (Yong and Finch 1997, p. 253; Service 2002, p. E-3). Migration stopover areas can be similar to breeding habitat or riparian habitats with less vegetation density and abundance compared to areas for nest placement (the vegetation structure is too short or sparse or the patch is too small) (Service 2002, p. E-3). For example, many locations where migrant flycatchers were detected on the lower Colorado River (Koronkiewiczet al.2004, pp. 9-11) and throughout Arizona in 2004 (Munzeret al.2005, Appendix C) were areas surveyed for nesting birds, but no breeding was detected. Such migration stopover areas, even though not used for breeding, are critically important resources affecting productivity and survival (Service 2002, p. E-3). The variety of riparian habitat occupied by migrant flycatchers ranges from small patches with shorter and sparser vegetation to larger more complex breeding habitats.

Therefore, based on the information above, we identify streams of lower gradient and more open valleys with a wide or broad floodplain an essential physical or biological feature of flycatcher habitat. In some instances,streams in relatively steep, confined area can also support flycatcher breeding habitat (Service 2002, p. D-13). These areas support the abundance of riparian vegetation used for flycatcher nesting, foraging, dispersal, and migration.

Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements Food

The flycatcher is somewhat of an insect generalist (Service 2002, p. 26), taking a wide range of invertebrate prey including flying, and ground- and vegetation-dwelling species of terrestrial and aquatic origins (Drostet al.2003, pp. 96-102). Wasps and bees (Hymenoptera) are common food items, as are flies (Diptera), beetles (Coleoptera), butterflies, moths and caterpillars (Lepidoptera), and spittlebugs (Homoptera) (Beal 1912, pp. 60-63; McCabe 1991, pp. 119-120). Plant foods such as small fruits have also been reported (Beal 1912, pp. 60-63; Roberts 1932, p. 20; Imhof 1962, p. 268), but are not a significant food during the breeding season (McCabe 1991, pp. 119-120). Diet studies of adult flycatchers (Drostet al.1998, p. 1; DeLayet al.1999, p. 216) found a wide range of prey taken. Major prey items were small (flying ants) (Hymenoptera) to large (dragonflies) (Odonata) flying insects, with Diptera and Hemiptera (true bugs) comprising half of the prey items. Willow flycatchers also took non-flying species, particularly Lepidoptera larvae. From an analysis of the flycatcher diet along the South Fork of the Kern River, California (Drostet al.2003, p. 98), flycatchers consumed a variety of prey from 12 different insect groups. Flycatchers have been identified targeting seasonal hatchings of aquatic insects along the Salt River arm of Roosevelt Lake, Arizona (Paxtonet al.2007a, p. 75).

Flycatcher food availability may be largely influenced by the density and species of vegetation, proximity to and presence of water, saturated soil levels, and microclimate features such as temperature and humidity (Service 2002, pp. 18, D-12). Flycatchers forage within and above the tree canopy, along the patch edge, in openings within the territory, over water, and from tall trees as well as herbaceous ground cover (Bent 1960, pp. 209-210; McCabe 1991, p. 124). Flycatchers employ a “sit and wait” foraging tactic, with foraging bouts interspersed with longer periods of perching (Prescott and Middleton 1988, p. 25).

Therefore, based on the information above, we identify the presence of a wide range of invertebrate prey, including flying and ground- and vegetation-dwelling species of terrestrial and aquatic origins to be an essential physical or biological feature of flycatcher habitat.

Water

Flycatcher nesting habitat is largely associated with perennial (persistent) stream flow that can support the expanse of vegetation characteristics needed by breeding flycatchers, but there are exceptions. Flycatcher nesting habitat can persist on intermittent (ephemeral) streams that retain local conditions favorable to riparian vegetation (Service 2002, p. D-12). The range and variety of stream flow conditions (frequency, magnitude, duration, and timing) (Poffet al.1997, pp. 770-772) that will establish and maintain flycatcher habitat can arise in different types of both regulated and unregulated flow regimes throughout its range (Service 2002, p. D-12). Also, flow conditions that will establish and maintain flycatcher habitat can be achieved in regulated streams, depending on scale of operation and the interaction of the primary physical characteristics of the landscape (Service 2002, p. D-12).

In the Southwest, hydrological conditions at a flycatcher breeding site can vary remarkably within a season and between years (Service 2002, p. D-12). At some locations, particularly during drier years, water or saturated soil is only present early in the breeding season (May and part of June) (Service 2002, p. D-12). At other sites, vegetation may be immersed in standing water during a wet year, but be hundreds of meters from surface water in dry years (Service 2002, p. D-12). This is particularly true of reservoir sites such as the Kern River at Lake Isabella, California; Roosevelt Lake, Arizona; and Elephant Butte Reservoir, New Mexico (Service 2002, p. D-12). Similarly, where a river channel has changed naturally, there may be a total absence of water or visibly saturated soil for several years. In such cases, the riparian vegetation and any flycatchers breeding within it may persist for several years (Service 2002, p. D-12).

In some areas, natural or managed hydrologic cycles can create temporary flycatcher habitat, but may not be able to support it for an extended amount of time, or may support varying amounts of habitat at different points in the cycle. Some dam operations create varied situations that allow different plant species to thrive when water is released below a dam, held in a lake, or removed from a lakebed, and consequently, varying degrees of flycatcher habitat are available as a result of dam operations (Service 2002, p. 33). The riparian vegetation that constitutes flycatcher breeding habitat requires substantial water (Service 2002, p. D-12). Because flycatcher breeding habitat is often where there is slow-moving or still water, these slow and still water conditions may also be important in influencing the production of insect prey base for flycatcher food (Service 2002, p. D-12). These slow-moving water situations can also be managed or mimicked through manipulated supplemental water originating from sources such as agricultural return flows or irrigation canals (Service 2002, p. D-15).

Therefore, based on the information above, we identify flowing streams with a wide range of stream flow conditions that support expansive riparian vegetation as an essential physical or biological feature of flycatcher habitat. The most common stream flow conditions are largely perennial (persistent) stream flow with a natural hydrologic regime (frequency, magnitude, duration, and timing). However, in the Southwest, hydrological conditions can vary, causing some flows to be intermittent, but the floodplain can retain surface moisture conditions favorable to expansive and flourishing riparian vegetation. These appropriate conditions can be supported by managed water sources and hydrological cycles that mimic key components of the natural hydrologic cycle.

Sites for Germination or Seed Dispersal

Subsurface hydrologic conditions may in some places (particularly at the more arid locations of the Southwest) be equally important to surface water conditions in determining riparian vegetation patterns (Lichivar and Wakely 2004, p. 92). Where groundwater levels are elevated to the point that riparian forest plants can directly access those waters, it can be an area for breeding, non-breeding, territorial, dispersing, foraging, and migrating flycatchers. Elevated groundwater helps create moist soil conditions believed to be important for nesting conditions and prey populations (Service 2002, pp. 11, 18), as further discussed below.

Depth to groundwater plays an important part in the distribution of riparian vegetation (Arizona Department of Water Resources 1994, p. 31) and consequently, flycatcher habitat. Thegreater the depth to groundwater below the land surface, the less abundant the riparian vegetation (Arizona Department of Water Resources 1994, p. 31). Localized, perched aquifers (a saturated area that sits above the main water table) can and do support some riparian habitat, but these systems are not extensive (Arizona Department of Water Resources 1994, p. 31).

The abundance and distribution of fine sediment deposited on floodplains is critical for the development, abundance, distribution, maintenance, and germination of the plants that grow into flycatcher habitat (Service 2002, p. 16). Fine sediments provide seed beds to facilitate the growth of riparian vegetation for flycatcher habitat. In almost all cases, moist or saturated soil is present at or near breeding sites during wet and non-drought years (Service 2002, p. 11). The saturated soil and adjacent surface water may be present early in the breeding season, but only damp soil is present by late June or early July (Service 2002, p. D-3). Microclimate features (temperature and humidity) facilitated by moist or saturated soil, are believed to play an important role where flycatchers are detected and nest, their breeding success, and availability and abundance of food resources (Service 2002, pp. 18, D-12).

Therefore, based on the information above, we identify elevated subsurface groundwater tables and appropriate floodplain fine sediments as essential physical or biological features of flycatcher habitat. These features provide water and seedbeds for the germination, growth, and maintenance of expansive growth of riparian vegetation needed by the flycatcher.

Cover or Shelter

Riparian vegetation (described more in detail within theSites for Breeding or Rearing (or Development) of Offspringsection) also provides the flycatcher cover and shelter while migrating and nesting. Placing nests in dense vegetation provides cover and shelter from predators or nest parasites that would seek out flycatcher adults, nestlings, or eggs. Similarly, using riparian vegetation for cover and shelter during migration provides food-rich stopover areas, a place to rest, and shelter or cover along migratory flights (Service 2002, pp. D-14, F-16). Riparian vegetation used by migrating flycatchers can sometimes be less dense and abundant than areas used for nesting (Service 2002, p. D-19). However, migration stopover areas, even though not used for breeding, may be critically important resources affecting local and regional flycatcher productivity and survival (Service 2002, p. D-19).

Therefore, based on the information above, we identify riparian tree and shrub species (described in more detail below) that provide cover and shelter for nesting, breeding, foraging, dispersing, and migrating flycatchers as essential physical or biological features of flycatcher habitat.

Sites for Breeding, Reproduction, or Rearing (or Development) of Offspring Reproduction and Rearing of Offspring

Riparian habitat characteristics such as dominant plant species, size and shape of habitat patches, tree canopy structure, vegetation height, and vegetation density are important parameters of flycatcher breeding habitat, although they may vary widely at different sites (Service 2002, p. D-1). The accumulating knowledge of flycatcher breeding sites reveals important areas of similarity, which constitute the basic concept of what is suitable breeding habitat (Service 2002, p. D-2). These habitat features are generally discussed below.

Flycatchers nest in thickets of trees and shrubs ranging in height from 2 m to 30 m (6 to 98 ft) (Service 2002, p. D-3). Lower-stature thickets (2-4 m or 6-13 ft tall) tend to be found at higher elevation sites, with tall-stature habitats at middle- and lower-elevation riparian forests (Service 2002, p. D-2). Nest sites typically have dense foliage at least from the ground level up to approximately 4 m (13 ft) above ground, although dense foliage may exist only at the shrub level, or as a low, dense tree canopy (Service 2002, p. D-3).

Regardless of the plant species' composition or height, breeding sites usually consist of dense vegetation in the patch interior, or an aggregate of dense patches interspersed with openings creating a mosaic that is not uniformly dense (Service 2002, p. 11). Common tree and shrub species currently known to comprise nesting habitat include Goodings willow, coyote willow, Geyers willow, arroyo willow, red willow, yewleaf willow, pacific willow (Salix lasiandra), boxelder, tamarisk, and Russian olive (Service 2002, pp. D-2, D-11). Other plant species used for nesting have been buttonbush (Cephalanthus occidentalis), cottonwood, stinging nettle (Urtica dioica), alder (Alnus rhombifolia, Alnus oblongifolia, Alnus tenuifolia), velvet ash (Fraxinus velutina), poison hemlock (Conium maculatum), blackberry (Rubus ursinus), seep willow (Baccharis salicifolia, Baccharis glutinosa), oak (Quercus agrifolia, Quercus chrysolepis), rose (Rosa californica, Rosa arizonica, Rosa multiflora), sycamore (Platinus wrightii), giant reed (Arundo donax), false indigo (Amorpha californica), Pacific poison ivy (Toxicodendron diversilobum), grape (Vitus arizonica), Virginia creeper (Parthenocissus quinquefolia), Siberian elm (Ulmus pumila), and walnut (Juglans hindsii) (Service 2002, pp. D-3, D-5, D-9). Other species used by nesting flycatchers may become known over time as more studies and surveys occur.

Canopy density (the amount of cover provided by tree and shrub branches measured from the ground) at various nest sites ranged from 50 to 100 percent (Service 2002, p. D-3). Flycatcher breeding habitat can be generally organized into three broad habitat types—those dominated by native vegetation (typically willow), by exotic (nonnative) vegetation (typically salt cedar), and those with mixed native and those dominated by exotic plants (typically salt cedar and willow).