Ducks arriving
By Walter L. Meagher, March 16, 2007

Everyone is happy to see the ducks arriving in El Charco. Happy, too, to have one resident species, the Mexican black duck (Anas platyrhynchos), building a nest and raising young, if not on an island in the presa, then nearby. In coloration it is not spectacular, but it has the virtue of constancy. Coots, gallinules and rails form a family of birds distantly related to ducks; given the chance, they prefer feeding among reeds and do not seek open waters. American coots (Fulica americana) may often be seen paddling away from the shoreline, moving unhurriedly, with self-composure; they nest in El Charco.

There are 308 species of ducks in the world and 24 in North America, ranging widely across the continent, nesting in northern parts and wintering south. In all, 12 species visit El Charco, but not all may be seen in one year. Ducks, unlike hummingbirds, who aggressively contest access to garden feeders with their own kind, are impressively collegial. When the presa is at its fullest (usually June-October, after the rains) and the sun at its brightest, the congregation of ducks on the water—ruddy ducks and pintails, both green-winged and blue-winged teal—is like a seaside resort in summer.

It is surprising to me that a dam as small as La Presa Las Colonias, which would be considered a small pond in Michigan, Wisconsin or Minnesota, is a haven for migratory waterfowl in Mexico. But just how watery are the places where visiting ducks breed and nest? Before we decide on an answer to that question, we need some inkling of where the ducks have come from. We know who arrives and when, how long he and she stay, but we do not know where they raise their young, or where they go when they leave El Charco, either to another winter feeding ground or home to spring and summer nesting sites. There are range maps in the best bird field guides, but they cannot be specific about our visitors.

Take the northern shoveler (Anas clypeata) as an example. Arriving in El Charco as early as September, this duck—with a bill longer than its head—stays seven months. The range map shows these ducks breed as far north as western Alaska, across the Canadian prairie provinces, as far south as Arizona and as far east as the Mississippi. The shoveler is one of three species that stay seven months in El Charco, but where does it come from, and by what flyway has it arrived? 

There are four flyways; the flyway most likely to provide passage for the ducks visiting El Charco is the one that funnels down east of the Rockies as far as the western side of the Mississippi River. But since the breeding range of the shoveler extends from the Yukon to Arizona, we can’t say how long a journey has been made. Imagine shovelers coming from one of the Canadian prairie provinces—the attraction of those prairies we shall see shortly—and having to hop, skip and jump from dam to dam where otherwise there are no lakes.

Alberta, Saskatchewan and Manitoba are the prairie provinces of Canada and all the species of ducks that visit San Miguel are known to include those provinces in their breeding ranges. The northern shoveler breeds as far north as the Aleutian Islands, but perhaps in migrating south they are satisfied to winter on a dam in Texas. The prairie provinces have the attraction of water. In Manitoba alone, lakes cover approximately 14.5% of its surface, or 94,241 KM2. 

The Islands in the Presa

Islands in the presa were made to attract ducks and other aquatics, giving them cover and possible nesting sites. There are now 13 islands—four were made in 2002, one in 2003 and eight in 2005, with grants from the Migratory Waterfowl Association of the United States, a splendid example of international cooperation between El Charco del Ingenio, A.C. and another conservation body.


Walter L. Meagher publishes technical research papers and writes on natural history subjects in a monthly column for The Deddington News, England. Last year saw the successful publication of his book, Portrait of a River. Most recently he has completed a revision of his study of the flora of El Charco, first published in 1994, and now the second edition is scheduled for publication, in Spanish, in 2007.