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<br />002697 <br /> <br />W AIS Document Retrieval - <br /> <br />the conservation of the species and that may reqUire special management <br />considerations or protection. Such requirements include but are not <br />limited to the following: (1) Space for individual and population <br />growth; (2) food, water, air, light, minerals, or other nutritional or <br />physiological requirements; (3) cover or shelter; (4) sites for <br />breeding, reproduction, rearing of offspring, germination, or seed <br />dispersal; and (5) habitats that are protected from disturbance or are <br />representative of the historic geographical and ecological <br />distributions of a species. The Service is proposing to designate as <br />critical habitat areas which provide or with rehabilitation will <br />provide the above five physical and biological features and primary <br />constituent elements. <br />For all areas of critical-habitat designated here, these physical <br />and biological features and primary constituent elements are provided <br />or will be provided by dense thickets of riparian shrubs and trees <br />(native and exotic species). This vegetation, by definition, occurs <br />near rivers, streams, open water, cienegas, marshy seeps, or saturated <br />soil. Constituent elements of critical habitat include the riparian <br />ecosystem within the 100-year floodplain, including areas where dense <br />riparian vegetation is not present, but may become established in the <br />future. The species composition of vegetation ranges from nearly <br />monotypic stands (i.e., single species) to stands with multiple species <br />(see Sogge et al. 1997). Vegetation structure ranges from simple, <br />single stratum patches as low as 3 meters (9 feet) in height and <br />lacking a distinct overstory to complex patches with multiple strata <br />and canopies nearing 18 meters (60 feet) in height. Vegetation patches <br />may be uniformly dense throughout, or occur as a mosaic of dense <br />thickets interspersed with small openings, bare soil, open water, or <br />shorter/sparser vegetation. Riparian patches used by breeding <br />flycatchers vary in size and shape, and may be relatively dense, linear <br />contiguous <br /> <br />[[Page 39133]] <br /> <br />stands or irregularly-shaped mosaics of dense vegetation with open <br />areas. The size of vegetation patches or habitat mosaics used by <br />southwestern willow flycatchers varies considerably and ranges from as <br />small as 0.8 hectares (2 acres) to several hundred hectares. However, <br />narrow linear riparian patches only one to two trees deep that have no <br />potential (absent limiting factors) to increase in depth are not <br />considered breeding habitat, although they may be used by southwestern <br />willow flycatchers during migration. <br />A total of approximately 964 km (599 miles) of stream and river are <br />being designated as critical habitat. The areas described were chosen <br />for critical habitat designation because they contain the remaining <br />known southwestern willow flycatcher nesting sites, and/or formerly <br />supported nesting southwestern willow flycatchers, and/or have the <br />potential to support nesting southwestern willow flycatchers. All areas <br />contain or with restoration will contain suitable nesting habitat in a <br />patchy, discontinuous distribution. This distribution is partially the <br />result of natural regeneration patterns of riparian vegetation (e.g. <br />cottonwood-willow). The distribution of these habitat patches is <br />expected to shift over time. Because of this spatial and temporal <br />distribution of habitat patches, it is important that the entirety of <br />the proposed river reaches be considered critical habitat. All areas <br />contain some unoccupied habitat or former (degraded) habitat, needed to <br />recover ecosystem integrity and support larger southwestern willow <br />flycatcher numbers during the species' recovery. A number of separate, <br />protected, healthy populations of southwestern willow flycatchers are <br />needed to protect the species from extinction by functioning as <br />population sources (Pulliam 1988). Protection of this proposed critical <br />habitat should ensure sufficient quantity and quality of habitat to <br />stabilize and recover this species. The southwestern willow flycatcher <br />is already extirpated from a significant portion of its former range. <br /> <br />Tuesday, July 22, 1997 <br /> <br />Page 8 of21 <br /> <br />2:0S PM <br />