Mexico - Spring Migration Along the Lower Colorado River (1 Viewer)

I visited this area in mid-late April as part of a larger team of researchers to investigate the effects of a large water release (“pulse flow”) into the Colorado River channel. Scientists from both Mexico and the US were out in force, measuring water flow, seed dispersal, and seedling sprouting - I was there to observe the foraging behavior of birds. While it is too soon to speculate on how well the birds are responding to the pulse flow, I can share my experiences with the area's birds and provide information to anyone interested in visiting the area.

Logistics:

Most of the study areas were public lands that could be visited by anybody, although they were generally not well-signed (except Cienega Santa Clara) and interested birders should contact a local guide for directions or assistance getting to the sites (see http://mexicobirdingtrail.org/plan-a-trip/colorado-river-delta/). I had no trouble getting around in my car (although I ALMOST get stuck on an unfamiliar "road" that abruptly turned into a long sand pit...:t: but this wasn't on the way to the sites described here), but then again I'm willing to take my junker onto anything I feel I can get away with- others might feel better using a truck, although 4x4 shouldn't be necessary. Conditions on the road to Cienega Santa Clara though are apparently subject to frequent change, even in the two-week span I spent there; sand piled up rapidly one evening during a dust storm.

There are hotels in the border town of San Luis Rio Colorado, and all sites can be reached within an hour and a half from there. Gas and delicious tacos are available in the small town of Luis B. Sanchez, closer to these sites. I can’t attest to any of lodging options - I was hosted by Juan Butrón at his house in a tiny community near Cienega de Santa Clara.

I crossed the border twice, and neither time did the Mexican authorities even look at my passport or stamp it. Not sure what would have happened had I been detained in Mexico for any reason - to be safe, one might want to get a Mexican tourist visa at the consulate in Yuma ahead of time. Returning to the US took at least a half hour of waiting in line both times.

map of the general area; for orientation, the US is just north of Sonora Highway 2, Yuma is about 20-30 miles north of San Luis Rio Colorado

One last bit of logistics I neglected to mention above: you do not need a vehicle import permit to drive to your own car to these parts of Mexico.

El Doctór

El Doctór is a nature reserve that protects 1850 acres of wetland within the Colorado River Delta in Mexico, providing critical habitat for marshbirds (including the threatened Yuma Clapper Rail) and stopover habitat for migrating shorebirds and songbirds. It is one of the first places with trees and water that northbound migrants encounter after crossing the Sea of Cortez or large stretches of surrounding Sonoran Desert- and as you can see from the map, the desert around here is VERY sparse and dry, quite unlike the relatively lush saguaro-palo verde-mesquite desert scrub around Tucson. Hence I saw the largest concentrations of migrants during my visits to this site.

I visited this spot twice, and the first time especially I was blown away by the visible migration. Warblers, buntings, grosbeaks, and tanagers hopping from tree to tree in a clear south-north pattern, mirrored above by a river of swallows (mostly Barn and Northern Rough-winged that day), Vaux's Swift, and Yellow-headed Blackbirds. Virtually every widespread western North American warbler was present: Yellow-rumped, Yellow, Wilson's, Nasvhille, Townsend's, Orange-crowned, and Black-throated Gray Warblers, and Common Yellowthroat. Out in the shallow water were shorebirds: Black-necked Stilt, Long-billed Dowitcher, Least and Western Sandpipers, and Wilson's Phalarope. Whimbrels occasionally flew over, here and farther inland along the river. This is a great spot for rails too, and over the course of both visits I heard all four regular species: Yuma Clapper Rail, Virginia Rail, Sora, and even a mid-morning surprise Black Rail! Year-round residents included Greater Roadrunner, Crissal Thrasher, Black-tailed Gnatcatcher, Verdin, Abert's Towhee, and Gambel's Quail.

Reports of lawlessness these past few years in northern Mexico would keep me away from the region. Was that on your mind also?
Any idea what the yellow flowering shrub is?

Steve

Hamhed said:

Reports of lawlessness these past few years in northern Mexico would keep me away from the region. Was that on your mind also?

Click to expand...

It was in the back of my mind, but I followed the standard safety precautions and wasn't overly concerned. In recent years most of the violence has been centered around the Texas border area, with less in Sonora generally and especially in this particular part of Sonora. It also helped that I was working with natives of the region who knew of the few potentially dangerous areas, which were not around the sites I describe here and were limited to the immediate border area between San Luis Rio Colorado and Algodones - an area that I worked in for a few days, but won't talk about much here because it wasn't particularly interesting and is difficult to access anyway.

Hamhed said:

Any idea what the yellow flowering shrub is?

Click to expand...

Not yet - in fact I took that photo for the purpose of later identification (Wilson's Warblers were foraging in them), but I couldn't find it in any of my plant books.

Cienega de Santa Clara

This is an even larger area of wetland a bit north of El Doctór - 14,000 acres of cattail marsh, critically important for the Yuma Clapper Rail. Another literal oasis in the desert, the last few kilometers of the road to the cienega pass through bare sand completely devoid of vegetation, bringing to mind the Sahara or another planet entirely! Juan treated me and a trio of Canadian journalists to a long boat ride through the cienega on my first full evening in Mexico. American Coots bobbed on the water throughout and handsome male Cinnamon Teal caught the evening sunlight. After an hour of gliding quietly through the dense cattails, we reached a shallow area on which hundreds of shorebirds had gathered. Black-necked Stilts, American Avocets, and Long-billed Dowitchers dominated the scene, and the sound of a hundred American Coots running on the water’s surface as they fled our boat sounded like a thunderous ocean wave. During a second visit to the cienega another evening, I explored the shoreline, mostly short pickleweed and a few scraggly tamarisks. Migrant warblers were using this area, especially Yellow-rumped Warblers (Audubon’s race), many of which were sallying and tumbling after invisible flying insects. A large flight of Tree Swallows came by, a stream of them that lasted a good forty minutes. Song Sparrows sang from the edge of the pools, and a few shorebirds stopped by now and then, a Least Sandpiper obligingly foraging in the late evening sunlight mere meters from me. The cattails resounded with the calls of Yuma Clapper Rail, Virginia Rail, Sora, and Least Bittern.

Rio Colorado Restoration Sites

I made numerous visits to many places along the Rio Colorado, but Pronatura Noroeste has some nice restoration areas along the river not far outside Luis B. Sanchez. Workers have removed large stands of invasive tamarisk and have replaced them with native mesquite, cottonwood, and willow. The plots are in various stages of development - there are bare fields with Horned Larks singing their tinkling songs from the sky, plots with cottonwoods no taller than me, and dense thickets with mature willow and mesquite (these were favored by the warblers). The sound of Ring-necked Pheasants from the surrounding wheat fields brought incongruous memories of a summer working in Iowa - apparently this species is expected here, but it had not been on my radar! The larger trees and open spaces provided habitat for Bullock’s Orioles and many flycatchers - Vermillion Flycatchers, brilliant red balls of fluff performing their fluttering flight songs; pugnacious Western Kingbirds; Ash-throated Flycatchers investigating nest holes. Lesser Nighthawks coursed by in broad daylight, and Burrowing Owls frequently flushed from the dirt levees. Remaining areas of tamarisk housed rasping families of Black-tailed Gnatcatchers, skulking Crissal Thrashers, and Greater Roadrunners. The river itself held plenty of slow-moving water and dense marsh vegetation, with rails, Marsh Wrens, Caspian Terns, and Pied-billed Grebes.

What a great area to cover during migration - and love that avocet!

Cheers
Mike