The Colorado River Delta is one of the most important wetlands of the Sonoran Desert. The nearly 250,000 acres of natural areas in the delta include riparian woodlands, an extensive floodplain, brackish marshes, and large estuarine areas. You can find over 360 species of birds in the delta throughout the year, making it one of the areas with highest diversity of birds in northwestern Mexico. Nearly 200,000 shorebirds and 60,000 ducks and geese use the delta each year as wintering grounds or for stopover habitat during migration and at least 110 species of landbirds visit the region during their migrations.
A number of bird species of conservation concern can be found in the delta, including: California Black Rail (endangered in Mexico), the endemic Yuma Clapper Rail (Threatened in Mexico and Endangered in the United States), Least Tern (under Special Protection in Mexico), Bald Eagle (Protected in Mexico), Southwestern Willow Flycatcher (Endangered in the United States), “Large-billed” Savannah Sparrow (under Special Protection in Mexico), Snowy Plover (Threatened in Mexico), and Bell’s Vireo.
The Colorado River delta is recognized as a Wetland of International Importance by The Ramsar Convention, is an Important Bird Conservation Area in Mexico, and is a priority wetland under the North American Wetland Conservation Act. It is also part of the Upper Gulf of California and Colorado River Delta Biosphere Reserve, a priority site for the conservation of biodiversity as decreed by the National Commission on Biodiversity, a site of hemispheric importance in the Western Hemisphere Shorebird Reserve Network, and a Sonoran Joint Venture Focus Area.
Within the Delta, the Mexico Birding Trail focuses on four sites: the Ciénega de Santa Clara, Cila/Laguna Grande, Las Arenitas, and the El Doctor wetlands.
Best Season to Visit: Spring and Winter
Amenities All of the sites at the Colorado River Delta have hiking trails. Other amenities are limited.
Ciénega de Santa Clara
The Ciénega de Santa Clara is the largest marsh in the Sonoran Desert, encompassing over 14,000 acres of cattail dominated areas interspersed with open lagoons, and nearly 30,000 acres of shallow pools and mudflats that extend towards the Upper Gulf of California. The Ciénega is maintained by discharge of agricultural wastewater from the Welton-Mohawk Irrigation District via the main outlet drain extension canal and local agricultural drain water. It is home to the largest population of Yuma Clapper Rails in the world, as well as a major portion of the population of the desert pupfish. It is a major stopover for migratory waterfowl on the Pacific Flyway, and support different human activities such as ecotourism, hunting, and fishing. In 1993, the Ciénega was included in the Upper Gulf of California and Colorado River Delta Biosphere Reserve.
Habitat: Dominated mostly by emergent plants, such as cattail, bulrush, and reeds. Shallow lagoons in the south of the Cienega have some Distchlis (seagrass) stands. Mesquite, saltcedar, quailbush, and agricultural fields surround the region, as well as several rural communities (ejidos).
The “Las Arenitas” Water Treatment Plant is a large open water pond created by treated wastewater. It provides important habitat to waterfowl and waterbirds, particularly during migration.
Habitat: Dominated to cattail, patches of willow and cottonwood. You can also see typical Sonoran Desert vegetation, including mesquite, ironwood, and saltbush.
Laguna Grande, located in the riparian corridor of the Colorado River in Mexico, includes channels, oxbows, backwater, and pond areas and providing diverse habitat to birds and other wildlife.
Habitat: Cottonwood-willow gallery forest, and a mixture of tamarisk, mesquite, and quailbush stands.
El Doctor Wetlands
The El Doctor wetlands extend along the escarpment that separates the Sonoran Desert Mesa with the Colorado River delta floodplain. The wetland complex, which is fed by natural springs, includes about 1850 acres of marsh, microphyll woodland, salt flats, and open water areas. These wetlands support 22 species of plants, including mesquite and saltcedar stands, surrounded by creosote bush-dominated dune vegetation.
Habitat: Dominated by cattails, bulrush, and other emergent plants in areas flooded. You can also see mesquite forest, creoste bush, and, unfortunately saltcedar, which is an introduced invasive tree.
Hire A Local Guide
- El Doctor and Ciénaga de Santa Clara – contact Alejandra Calvo Fonseca, Pronatura Noroeste, Phone: 001 52 (653) 535-6738, email: email@example.com
- Las Arenitas and CILA/Laguna Grande – contact Edith Santiago, Sonoran Institute, Phone: 001 52 (686) 582-5431, email: ESantiago@sonoraninstitute.org
- Colorado River Delta Bird Checklist (from Hinojosa-Huerta O., J. García-Hernández, Y. Carrillo-Guerrero, and E. Zamora-Hernández. 2007. Hovering over the Alto Golfo: the status and conservation of birds from the Rio Colorado to the Gran Desierto. Pp 383-407. In: Dry Borders: Great Natural Reserves of the Sonoran Desert. Felger RS, Broyles B, (eds). Salt Lake City, Utah. University of Utah Press.)
Pronatura Noroeste’s Colorado River Delta Initiative, which began in 2002, includes a year-round bird monitoring program, including marshbird surveys, point counts in riparian areas, mist-netting, vegetation surveys, and surface and groundwater monitoring. It provides critical information for understanding trends of bird populations and habitats in the delta, as well as relationships with water flows and management strategies. Pronatura is also deeply involved with securing water rights for the Delta, as well as habitat restoration and protection efforts. The initiative also provides additional training and employment opportunities for bird guides.
The Sonoran Institute, which works closely with Pronatura Noroeste on many projects in the region, has an ambitious goal of doubling the Delta’s existing wetlands by protecting and restoring more than 160,000 acres over the next 20 years. In the next ten years they plan to develop several areas of healthy terrestrial and aquatic habitat by planting native trees and securing an instream flow of at least 25,000 acre-feet. Each year they will enhance approximately 100 acres of riparian habitat and 100 acres of marsh wetlands, with the goal of creating two ecologically functional demonstration sites by 2017: the Colorado River restoration Demonstration Site (4,400 acres), which includes the Laguna Grande and Laguna Roja, and the Lower Hardy River Demonstration Site (4,500 acres), which includes the Hardy River Ecological Camp and Las Arenitas Wetland (described above).
Some of Pronatura’s and the Sonoran Institute’s restoration efforts have taken place at a site known as Laguna Grande and in the Limitrophe Section of the river, at Colonia Miguel Aleman. It includes channels, oxbows, backwater, and pond areas, providing diverse habitat to birds and other wildlife. The project ensured the protection of 1,200 acres for restoration by obtaining the concession of federal lands. Pronatura has also been doing active restoration on 60 additional acres, planting over 10,000 cottonwoods, willows, and mesquite trees, in collaboration with Sonoran Institute, the local organization AEURHYC (The Ecological Association of Users of the Hardy and Colorado Rivers), and local communities. As part of the process, Pronatura acquired irrigation rights (1,400 acre-feet of water per year) to dedicate flows to maintain the wetland and riparian areas. Bird guides highlighted on this website participated as volunteers in the restoration work, clearing salt cedar, planting and irrigating over 30,000 trees, and helping to construct a nursery to produce native vegetation.
The “Las Arenitas” Water Treatment Plant is part of the Mexicali II wastewater treatment system, which was built between 1999 and 2007. Nearly a third of the treated effluent goes to the Hardy River, improving habitat for birds and other wildlife. As part of the process of environmental restoration, the Mexicali State Commission for Public Services (Comisión Estatal de Servicios Publicos de Mexicali – CESPM), supported by Sonoran Institute and Pronatura Noroeste, have implemented a project to build a 247 acre artificial wetland within the treatment plant complex, which both helps improve water quality and creates habitat for wildlife.
Pronatura Noroeste has been working with the community of Ejido El Doctor to establish a conservation easement on 500 acres to protect key stopover sites for Neotropical migratory birds and nesting areas for protected species, such as Black Rail and Snowy Plover. Part of the project includes fencing the area to exclude cattle and the restoration of 40 acres within the protected site. Bird guides help as volunteers on this project, setting up fence and planting trees (mesquite, cottonwood, and willow).
Pronatura Noroeste and the Sonoran Institute work closely with U.S. and Mexican governmental and non-governmental organizations, local communities, indigenous tribes, schools, and universities to develop projects that have lasting, long-term positive impacts on both the ecosystems and the communities that depend upon them.
- Books and reports of interest
- Bird Conservation Plan for the Colorado River Delta
- Details about the work of Pronatura Noroeste in the region
- Details about the work of the Sonoran Institute in the region
- Death of a River: The Colorado River Delta (9 minute video by Alexandra Cousteau tracing the path of the river from the U.S. Mexico border to its mouth in the Gulf of California)
- Bringing Back the Colorado River Delta (6 minute video by the New York Times about water rights and habitat restoration)