Thursday, September 24, 2009

Winter hummers

It's late September. Got a hummingbird in your yard?

Most people think of hummingbirds as tropical, and indeed most of them are. But a fair number of species have moved quite far north into the United States (including Alaska!) and Canada since the last glaciers receded. The Southwest has a great diversity of species, as many as 15 species breeding north of the Mexican border. But many of the border species migrate south for the winter, and all that occur north of the border region are migrants to Mexico and beyond, except one—Anna’s Hummingbird (Calypte anna).

This species was historically resident in southern and central California and northern Baja California, areas that remained warm enough in winter that the birds could remain through the cold season and find enough insects and winter-blooming flowers to sustain them. But that was then, and this is now. Over a half century ago, people discovered they could attract hummers to their yard by hanging out special feeders filled with sugar water, typically one part sugar dissolved in four parts water. It worked like a charm. People feed hummers all over North America now, and birders gather to watch these birds at southern localities with dozens of feeders and, sometimes, hundreds of hummers. These sites are especially rich during fall migration, as hummingbirds are streaming south through the western states on their way to Mexico.

All species may have benefited from the existence of these feeders, but none more than Anna’s. This species has extended its breeding range all the way north to southern British Columbia and east to the Arizona-New Mexico border, with occasional breeding attempts even outside this range. Nonbreeders have wandered east as far as Minnesota and Florida and north to southern Alaska.

Several other species of hummingbirds (Black-chinned, Rufous, Calliope) nest widely in the Pacific Northwest, but all except Anna’s leave in late summer and head for Mexico, not to return until the following spring. Anna’s is supremely adapted to live with people, taking advantage of nonnative plantings and feeders in a way the other species have not been able to do, and this has allowed it to overwinter in regions apparently too cold and/or food-free for the other species. All hummingbirds go into torpor during low temperatures at night, so why can’t the other species take advantage of feeders that are provided throughout the winter? Perhaps the fact that Anna’s was resident in the first place, with no genes for migratory behavior, allowed it to be perfectly adapted to take advantage of the changes we make in the natural world.

Dennis Paulson

1 comment:

Lindy said...

I enjoyed reading your blog today and found it to be especially informative about the Anna's Hummingbird. (I also liked your "feeding birds" blog).

Living in Southern California, I feel very fortunate that I get to feed and enjoy the hummingbirds year round. Of course, in addition to the hummingbird attracting plants I've included in my garden, I make sure the hummingbird feeders are kept full.

During the winter months, my East Coast friends are quite envious as I chat with them and tell them about the hummingbird friends that I had visit that day. Sometimes I think that having the hummingbirds here year round, makes up for all the unexpected shaking and quaking we get from time to time.

Keep up the good work!