Site Description: The IBA is the Salt River from 83rd Avenue, connecting with the Gila River at 115th Avenue and extending west and south along the Gila River to the Gillespie Dam.The Arizona Game and Fish Department operates four designated wildlife areas and several additional parcels of owned or managed lands along the Gila River (owns 3780 acres/manages +8500 acres). Additional ownership is under Arizona Lands State Trust, Maricopa County Regional Park, and Bureau of Land Management. The Gila River has perennial flow, the source of this water is from treated effluent from the City of Phoenix and other communities (Tres Rios Wetlands at 83rd Ave.), excess agriculture water, and from natural ground water. Sonoran Audubon Society is the steward for this IBA. They conduct bird surveys primarily during winter and migration. The Tres Rios Wetlands are an outstanding site and home to a nesting colony of Neotropic cormorants, a qualifying species for the global designation of this IBA. Visit http://phoenix.gov/waterservices/tresrios/wetlandsresearch/index.html for more information and how to access the wetlands to bird. The Tres Rios and Gila River Christmas Bird Count circles include this IBA. Visit the Arizona IBA web site for access to data at http://aziba.org
The area has a rich productivity of plant growth due to the perennial supply of nutrient laden waters. The fish community is considered to be one of the most abundant in Arizona, and consequently, the numbers and diversity of fish-eating birds is phenomenal. Egrets and herons are exceptionally abundant, with annual Audubon Christmas Bird Counts (CBC) enumerating several hundred of these species (Great Egret, Great Blue Heron, Black-crowned Night Heron, Snowy Egret, and Double-crested Cormorant). Ospreys are regular winter residents, common in migration, and have attempted to nest in recent years. A Bald Eagle pair has successfully fledged young in 2010 and 2011. too, and Neotropical Cormorant are regularly in mixed groups with Double-crested Cormorant. Long-billed Curlew are passage visitors that are documented on the Gila River Christmas Bird Count. Yuma Clapper Rails reach their upstream limit of distribution on the Gila River in this IBA, and are widely distributed within preferred habitat. Least Bittern is also relatively common. Secretive marsh bird surveys are conducted annually in this IBA and the data is entered into the National Marsh Bird database. Abert's Towhee are particularly abundant, with the U.S. highest counts for the CBC occurring in this IBA. Many raptors winter along the river corridor in this area, especially the Northern Harrier and Cooper's Hawk, along with Osprey, Red-tailed Hawk, Sharp-shinned Hawk, and Prairie and Peregrine Falcon. The White-tailed Kite has nested on the Robbins Butte Wildlife Area (1999). Swainson's Hawk migrates through in the fall and spring in large numbers (500 Avg.).
Invasion of salt cedar is a concern and difficult to manage because of regulated releases of water from upstream impoundments. Loss of effluent water due to diversion by the City of Phoenix, and other communities is considered a long-term serious threat. Water quality may impact reproductive performance due to pesticide run-off from agricultural lands, and pharmaceuticals in the effluent water. High human use threatens to disturb nesting birds, and lack of access control contributes to illegal dumping, and risk of accidental fire due to human use in the area. Cowbird population is abundant and may be impacting Neotropical migratory nesting birds in particular.
The Arizona Game and Fish Department operates four designated wildlife areas and several additional parcels of owned or managed lands along the Gila River (owns 3780 acres/manages +8500 acres). Additional ownership is under Arizona Lands State Trust, Maricopa County Regional Park, and Bureau of Land Management.
The area is classified as lower elevation Sonoran riparian and adjacent xero-riparian habitat. Vegetation is composed of Fremont cottonwood and Gooding willow stringers along the active channels of the river, and in remnant stringers along old channels. Back from the active channel are salt cedar, seep willow, mesquite, palo verde, and other shrubs. Mature cottonwood/willow gallery forest is sparse, and occurs in patches, notably at 115th Avenue, near Jackrabbit Road, and a few other places. Most willows and cottonwoods are of the younger age class. Emergent and aquatic plants are well distributed throughout the reach. Adjacent irrigated farmland provides winter and migration habitat for raptors and water birds.
Land use is mixed, including flood control, agriculture, water treatment, nature conservation, and recreation including hunting and fishing.
Protected Areas: Four state Wildlife Management Areas are managed for hunting, bird-watching and other outdoor recreation activities.
The annual Tres Rios Nature Festival is held at this IBA in February or March.