For the Birds Radio Program: Cape May Warbler

Original Air Date: May 27, 2004 (estimated date)

Laura’s been enjoying Cape May Warblers, up close and personal.

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Transcript

Cape May Warbler

Many times over the years, I’ve tried to pick a favorite warbler only to realize that I have a lot of favorites. But one warbler that wasn’t a particular favorite was the Cape May. It’s not that I didn’t like it, but somehow it never stood out in my mind or heart. At least not until this year. With the early spring in April, and then the cool weather in May, many warblers headed north early only to arrive before a good supply of insects was available to sustain them. Some of the early birds succumbed to the cold or to starvation, though many managed to hang in there. The ones best-equipped to handle the situation were the two species that are capable of digesting foods other than insects. Yellow-rumped Warblers have unusually long intestines and produce an enzyme which enables them to digest the waxy coatings on berries. And Cape May Warblers have a tubular tongue, like a hummingbird, enabling them to sip on sap when insects are scarce. The books talk about their ability to sip sap thanks to that specialized tongue, but don’t seem to mention another very important adaptation—when a Cape May Warbler discovers a suitable feeding source, it spends part of its time eating, and a great deal more time chasing away potential competitors, both its own kind and other species. I’ve watched a Cape May Warbler chase a relatively huge sapsucker from the poor woodpecker’s own drill holes.

Anyway, this all seemed interesting, but somehow didn’t grab at my heart until this year. On May 12, a Cape May Warbler appeared in my yard, and started feeding on the oranges and jelly I’d set out for my orioles. Soon there were two Cape Mays, and then three, and suddenly I had a whole flock of them—as many as 7 males and 8 females at once, each taking over an orange half, a bowl of jelly, or a hummingbird feeder. They came to my window feeders as well as feeders farther from the house, giving me close views and an opportunity to get some photos, even allowing me to observe at close range a feature I never knew Cape May Warblers have—the soles of the feet of adult males are brilliant yellow. I have no idea what adaptive value that might have, but it was pretty cool to actually see it and photograph it at close range.

One male Cape May took over the maple tree next to my office window. His preferred perch was a little branch about a foot from my hummingbird feeder. He could hover only for two or three seconds at a time before he’d return to the perch, the closeness of the branch allowing him to get the maximum amount of calories for the least amount of effort. The problem was, that’s the window my chickadees and nuthatches come to to get my attention when they want mealworms. Anytime one approached, the Cape May Warbler took chase. That technique worked fine when other birds came to the tree—they didn’t see anything special about one maple tree in a neighborhood filled with them, and saw no point to standing their ground. But my chickadees and nuthatches know for a fact that the maple tree belongs to them, and both these species consider aggressive chases to be bad form, so any time the Cape May dive-bombed them, they took evasive action while single-mindedly weaving toward the window. At least in the case of chickadees and nuthatches, apparently the meek do inherit the earth, or at least the maple tree.

The aggressiveness of Cape Mays reminds me quite a bit of the aggressiveness of hummingbirds. In both cases, the birds depend on a food source that can dry up, and when flowers are depleted of nectar, some never replace it and others take hours or days to replenish the supply. Defending them takes a lot of energy, but is apparently the right strategy during times of scarcity. On cold days, I could tell the Cape Mays were desperate for food. One male came to the hummingbird feeder until 9:35 pm, well after sunset, and the first one of the day appeared at 5:25, well before sunrise. Most of the time it was impossible to see more than one feeding at a time, but in early evening, suddenly several would crowd into some of my feeders at the same time.

Cape May Warblers nest in coniferous forests, not in backyards, so mine will assuredly be moving on any day. But the unexpected sparkle they’ve brought to my backyard has been a delight, and they’ve given me a special gift by allowing me to take such close photos. You can see these lovely birds up close and personal by going to my webpage, www.lauraerickson.com.