Nancy L. Newfield has been watching hummingbirds at her Louisiana home and lots of other places since 1975. Nancy lost her amateur status years ago, and now writes and lectures on hummers. She is co-author of Hummingbird Gardens, reviewed elsewhere on this site. Nancy is also a licensed hummingbird bander and a recognized authority on hummingbird distribution, behavior, and taxonomy.
Movin' Onmn air. Others see huge kettles of Broad-winged Hawks drifting along a mountain ridge. Vast flocks of shorebirds blanket coastal mudflats with thousands of individuals taking off in unison. These are three different kinds of avian seasonal movements, but hummingbird migration bears little resemblance to that of many other birds.
In fact, hummingbird migration encompasses many species, each moving in accord with its own genetically defined pattern and season. Individual birds may vary their movements considerably within the parameters of their species. From wintering grounds in Mexico and Central America, male Ruby-throated Hummingbirds arrive at their southernmost haunts in the United States by early March. And, females of that population may be initiating incubation while Ruby-throats that will nest in Minnesota and Michigan are yet enjoying the ambience of tropical hospitality.
Northward movement for members of the nominate (migratory) subspecies of the Allen's Hummingbird, which breeds along the Pacific coast of California, occurs during the winter months (for the northern hemisphere), with egg-laying and incubation beginning long before the vernal equinox. Rufous Hummingbirds begin arriving in the forests of the Pacific Northwest in late February. They, too, may have young on the way whilst Alaska breeding members of their kind are just establishing homesites. Therefore, the term "spring migration" is not particularly fitting. I prefer to use "northward migration," as this term is more directional.
Similarly, post-breeding or "southward migrations" are diverse with males of early nesting populations, especially Allen's and Rufous, departing well before the first calendar days of summer. Male Ruby-throats may be basking in the Mexican sun shortly after the summer solstice. Over the entire twelve month span of the year, some North American hummingbirds may be found to be migrating. Obviously, a single factor cannot be influencing all of them, or at least, not all in the same way.
Many people believe incorrectly that hummingbirds leave a region because of a shortage of nectar. But, most species begin their movements while native wildflowers are at or near their peak of bloom. If these birds waited until resources were scarce, they would not be capable of putting on the fat required to fuel their arduous journeys.
The month of August is probably the most exciting for hummingbirders around North America. Hordes of hummers crowd feeders and there is a satisfying sense of plenty. A successful nesting season will have doubled spring populations - and all the hummers, old and young, need extra nectar to be able to migrate.
Sites along any migration route see an enormous turnover of birds, with some individuals remaining only a few hours. And, unlike many other kinds of birds, hummers migrate singly. The presence of a large number only indicates that all have found the same resource. Propelled by an inborn impetus, most hummingbirds are movin' on.
Copyright © 1997
Nancy L. Newfield
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