Cape May Grapes

Cape May Warblers, John Cassin
Cape May Warblers, John Cassin

New birders learn early on, sometimes to their startlement, that birds are not distributed generally across the landscape. There’s this thing called habitat, you see, and as a well-known birder once wrote,

You would never expect to see a Meadowlark in the woods, although the Flicker might leave its grove of trees to dig up an ant’s nest at the edge of a field.

With a little experience behind us, most of us most of the time can remember that and many other of the often subtle relationships between birds and their environments. At least, that is, in the breeding season. We are — by which I suppose I mean “I am” — less keenly aware of the habitat preferences of the birds we see in migration and winter. And that’s a shame, since even in fall, when many southbound birds are more catholic in their choice of stopovers, a careful eye for certain landscape features can still increase your chances of running into some of the sought-after migrants.

Looking for migrating Connecticut Warblers? Check open field edges with dense stands of goldenrod and ragweed.

Wintering Sagebrush Sparrows? Look for patches of inkweed among widely scattered mesquites.

And autumn Cape May Warblers? Grapes seem to do the trick.

On September 12, 1914, at West Grove, Chester Co., Pa., … I observed three Cape May Warblers … feeding upon ripe grapes…. for several days a few of them might be seen at almost any time in the tree over which the grapevine grew.

Isaac Roberts‘s observation might seem just an incidental curiosity. But exactly a year earlier, Frank Burns had found that species to be “a destructive grape juice consumer at Berwyn, Pennsylvania,” where two trees in his yard had been taken over by “fugitive” grape vines:

on September 12, 1913, I took a specimen … and on the 14th and 15th observed twenty and thirty adult and immature female Cape Mays…. six shots failed to drive the survivors from the tree…. on the 20th, I saw an individual alight on a bunch of Niagara grapes, deliberately puncture the skin and eat greedily; this and several other specimens were taken with dripping bills.

Cape Mays gorged themselves on Burns’s grapes until October 7, 1913, laying on important energy reserves for the rest of their flight south:

Specimens secured early … were rather lean, but after some days of feeding became fat, inactive and even sluggish; an adult female shot in the act of eating from a grape … was positively enveloped in fat, and the skin became so saturated with oil I had the greatest difficulty in saving it.

The following year, Burns found Cape May Warblers in his grapevines beginning September 6; within ten days, his entire grape crop, red, purple, and white, was “utterly destroyed.” The last bird was seen six weeks later, on October 20.

Like Roberts, Burns’s neighbors suffered the same depredations:

complaints of the ‘little striped yellow bird’ were many, and so far as I am able to learn, all unbagged grapes were ruined; the loss must have been many tons worth several hundred dollars.

A century later, I’ll be paying special attention to grapevines these next few weeks.