For the Birds Radio Program: Migration Update 2007
May and September are the most happenin’ months of the year, when absolutely nothing is constant from day to day. Last week my yard was filled with Blue Jays—every time I counted them I tallied at least a hundred. They were pigging out at my feeders, eating berries, taking baths, resting, coming in from migratory flights, and taking off anew on migratory flights. This week I haven’t counted as many as a dozen at a single time, and many times when I look out I don’t find any. Even when they were most abundant, my yard was surprisingly quiet. I’d only hear a squawk when a hawk was flying in. Migrating hawks are also the order of the day in May and September, and since I’m right under Hawk Ridge, they’re wandering through my yard all the time this month.
Meanwhile, my lawn is crawling with sparrows—mostly White-throats and White-crowneds at this point, but soon Harris’s Sparrows and Fox Sparrows will be joining them. Juncoes are coming through now, too. I thought the White-throats had peaked last week, but I have twice as many this week. Purple Finches and goldfinches are also on the move, along with plenty of Red-breasted Nuthatches.
Warbler migration has already peaked, but quite a few warblers haven’t heard the news. This weekend I saw Blue-headed Vireos and several warbler species. They were mostly yellow-rumps and palms, but a smattering of redstarts, magnolia warblers, and other species added color and vivacity to the scene. My last hummingbirds cut out around September 6, but suddenly two more appeared on Friday, September 21st. This isn’t the latest ever for me seeing Ruby-throated Hummingbirds, but it’s close. The two I have appear to be an immature male and an immature female. Immatures normally leave later than adults. Adult male ruby-throats typically leave their breeding territories in late July or early August. Ones we see late in August and in early September are usually birds from much farther north that are passing through. Adult females leave as soon as their babies are independent and their own bodies are ready to face the rigors of migration. This leaves the dwindling supply of flowers and nectar for the young of the year, as they bulk up so they, too, can head south. Ruby-throats have a powerful instinct to migrate, and need insects as well as nectar. The ones in my yard are still feeding on lots of insects—I can see them darting here and there in hot pursuit of tiny bugs between the boughs of my trees. Once they’re properly plumped up, off they’ll go. But I’ll keep the feeders filled with fresh sugar water into December. The probability is extremely low that any rare hummingbirds will turn up—that’s the very definition of the word rare. But if I don’t keep the feeders out, I’ll have zero chance of seeing one. So keeping out a hummingbird feeder in late fall is like a free lottery ticket.
Scott Weidensaul, the extraordinary nature writer who wrote Living on the Wind: Across the Hemisphere with Migratory Birds, has postulated that right now we’re watching evolution taking place with hummingbird migratory routes. I think Rufous Hummingbirds, hardy enough to nest in the mountains of Alaska and northern Canada, are more likely to survive wintering in the southeastern United States than in Mexico, where so much deforestation is taking place. Even though plenty of them are still following the route used for millennia, the individuals who head southeast instead of due south, who before warmer winters would have succumbed for sure, are surviving and passing on their genes to a new generation of easterly-migrating Rufous Hummingbirds. And in this unpredictable season, other oddities are always possible, too. The rarest right now is a Green Mango—a tropical hummingbird who’s visiting a feeder in Beloit, Wisconsin. Migration is like a box of chocolates—you never know what you’re going to get.