Important Bird Areas

San Pedro Riparian National Conservation Area

Arizona

The San Pedro Riparian National Conservation Area is a protected area encompassing some 50 miles of the San Pedro River and adjoining habitats, it is the best example of desert riparian ecosystem in the United States. The area is managed by the Bureau of Land Management and is accessed by 6 paved road entry points.

Ornithological Summary

This IBA is one of the four major north-south migratory bird corridors of the southwestern United States, along with the Rio Grande, Santa Cruz, and the Colorado River. Bird densities during migration average 40 birds per hectare, and can reach 75 to 100 birds per hectare. Greatest abundance in migration are Yellow Warblers and Wilson's Warbler, but also using the corridor are Osprey, Common Black-Hawk, Olive-sided Flycatcher, Gray Flycatcher, and MacGillivray's Warbler. This IBA supports the largest breeding population of Gray Hawks in the U.S., 35-40 pairs (40% of the population), and the largest Yellow-billed Cuckoo population in the U.S., 41 pairs documented in 1999. The IBA supports migrating Southwestern Willow Flycatchers, which nest further downstream in great abundance between San Manuel and Winkelman. Two warbler species nest in tremendous number in this IBA, Lucy's Warbler within the mesquite bosque habitat, and Yellow Warbler within cottonwood/willow habitat. Green Kingfisher nest in the river banks with as many as 7 pairs in a given year. Botteri's (estimated 200 pairs) and Cassin's Sparrow (estimated 500 pairs) nest in the adjacent bunchgrass habitat in exceptionally high numbers. Other nesting species of conservation status (SCS) include, Abert's Towhee (very abundant), Elf Owl, Gilded Flicker, Northern Beardless-Tyrannulet, Tropical Kingbird, Crissal Thrasher, and Varied Bunting. Belted Kingfisher(SCS) and Red-naped Sapsucker (SCS) can be found regularly over-wintering along the river. Historically, both the Aplomado Falcon and Cactus Ferruginous Pygmy-Owl nested in the river valley. Mississippi Kite are breeding just north of the NCA (10 individuals). The IBA meets Global A1 threshold for breeding Bell' Vireo.

Conservation Issues

Urban, suburban, and ranchette development in the upper San Pedro Valley, and their resulting water use, causing the downward trend of the regional aquifer is the major threat to the future conservation of a flowing San Pedro River and high water table supportive of riparian vegetation critical to birds and other wildlife. Over draft of the aquifer from ever expanding and new subdivisions may ultimately dry the river at certain seasons and locations, unless strict growth and conservation measures are implemented. Unregulated wells from non-subdivision housing is also a concern. Illegal immigrants and their trails, trash, and potential to start fires are moderate to serious threats to the health of the riparian ecosystem. Greater BLM staffing is needed for resource protection patrols.

Ownership

The San Pedro River National Riparian Conservation Area is managed by the U.S. Bureau of Land Management (BLM).

Habitat

The gallery forest bordering the river is comprised Fremont cottonwood/Goodding Willow canopy, with a mid-story of seep willow, Arizona ash, and mesquite, and understory of grasses and forbs. Bordering this broadleaf forest in many places, is a mesquite bosque, and in other places by Sacaton grassland.

Land Use

This IBA is a National Conservation Area, managed by the Bureau of Land Management. Grazing is presently not allowed (cattle removed late 1987).

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