Viewing tabasco's Garden Diary: Hummingbird Notes on Migration and Identification
Wednesday, August 26, 2009
Identification tips from Kevin on the Hummingbird Forum
August 2009
From: Kevin Morgan in Baton Rouge LA.
Judy,
You asked two very good questions. I can help definitely with one and partly with the other (and surprise, the answers are related!).
>>1) How can anyone be sure that the HBs you are seeing at your feeders are the 'same pairs' or 'the same two males', or 'new arrivals', etc.?<
As Joan noted, it's often virtually impossible to be sure. Banding and color-marking birds frequently reveals more birds present than a homeowner believes, especially during migration.
For Ruby-throated Hummingbirds, young males are (sometimes) the easiest to distinguish from each other because they each have a pattern of stippling on the throat, sometimes coupled with one or more iridescent gorget feathers. The gorget pattern may be distinctive for a given bird. However, in migration, you might have twenty, thirty, or more immature males pass through your yard in a day's time, so you may not get the opportunity to learn a particular bird's gorget pattern before it's moved on.
Adult males, and all females, usually vary less from individual to individual, at least to the human eye. Rarely, though, a bird will have some sort of distinctive mark or color pattern that can be spotted.
Beyond that, and banding, it's simply not possible. People often tell us "But he perches in the same tree, on the same branch, every time I see him!" The problem is, he's perching on that branch for a reason: either it gives a good vantage point to guard a feeder, or to see predators coming, or something of that nature. If it's good for him, it's good for any other bird who comes along.
During September migrant banding at Nancy's regular site, we often see swarms of birds at the feeders - as many as twenty in view at a time, with more in the gardens adjoining. But we have banded, in a single day, as many as 97 birds, with many more not banded and not color-marked still being seen in the yard. Almost always, there were as many unbanded birds in view as banded ones. So there was a constant turn-over of birds throughout the day.
We've even gone to yards in winter and had a homeowner tell us she had 4 Rufous, maybe 5 - and caught 8 and a 9th one was spotted after we finished. Another yard, the homeowner knew he had at least 2 Buff-bellied Hummingbirds and was almost certain he had a third-but we caught and banded 7.
One note, though: with the proper skills, one can at least learn to readily distinguish adult from young, male from female, and so it's possible to recognize the first immature birds of the season. For folks like me, who don't have nesting birds nearby, I at least know when the first adult male, adult female, etc. are spotted. And of course, if you see one bird chasing another, you know you've got at least two.
(2) Do the HBs migrate along with weather fronts, do you think? And are there identified 'flyways' for fall migration?...
Fronts do seem to push birds in sometimes during migration, or push them out. It's not a guaranteed effect, but if a front is expected coming FROM an area where there are still a lot of hummingbirds, and it's fall migration, you may want to look to see what's coming in.
As for flyways: this term is widely used but often incorrectly. Properly used, it refers (in North America) to four broad general paths birds may take from points north to points south, and is really most meaningful with regards to waterfowl. However, they're not narrow bands; the Central flyway, for instance, stretches across Texas at its widest point, and the Mississippi Flyway is substantially wide as well.
Hummingbird migration is slowly coming into focus (or at least, becoming not quite as murky) as banding and recapture data shows us more about where birds winter vs. where they nest. However, we have extraordinarily few examples on which to base conclusions. We know that at least a few hummingbirds from South Carolina have been recaptured somewhat to the south and west of their banding site. There's one which was banded in the fall in eastern OK that was found dead the following June in Duluth, MN - which indicates that bird, the year it was banded, was probably following a path more or less due south. One banded in Ontario on September 15 of 2007 was recaptured in Sweeney, Texas on October 2 of that year, about 1135 miles as the crow flies, but the bird may have flown south, then west. There's a record of one bird banded near Hickory, NC recaptured in Rockport, TX 12 days later, again suggesting a west/southwest path.
What the limited data seem to suggest to me (and this is just my interpretation, though it's shared by some others) is that Ruby-throats generally migrate south and west, heading for the Texas Gulf Coast, and generally follow the coast down into Mexico and then spread out over southern Mexico and parts of Central America, as far as western Costa Rica. Whether birds from, say, Massachusetts would move south first, then west, or west first, then south, is hard to guess.
