Early migration

More and more birds are hitting the Island ahead of their expected dates.

A male prothonotary warbler was spotted in Sheriff’s Meadow Sanctuary in Edgartown. —Eugene Hester

Migration always interests birders, increasing diversity and numbers, and greatly increasing the odds of something unusual turning up. While fall probably brings the best birding to the Vineyard, spring migration generally brings its fair share of oddities. And even watching the return of our common migratory breeding birds is interesting.

So far, this spring migration has not disappointed. As usually happens, the arrival of our very first migrants — red-winged blackbirds and common grackles — took place as soon as winter started ease off, but was followed by weeks of generally dismal weather during which little seemed to be moving.

But the first half of April brought warmer temperatures and sustained southerly winds, and predictably, a pulse of incoming songbirds followed. A few notable rarities have already turned up, but the pattern even of arriving common species has been an interesting one.

The best bird of the season so far, hands down, was a black-necked stilt found in Edgartown — an odd-looking black-and-white shorebird with preposterous, lengthy, bubblegum-pink legs. But shorebirds move around according to their own logic, so for this column I’ll confine myself to songbirds.

Most significant among that group of species was surely a prime-looking male prothonotary warbler, found on April 8 by Maria Thibodeau at Sheriff’s Meadow Sanctuary in Edgartown. A beautiful species with a bright orange head and chest, the prothonotary warbler falls into the class of “regular rarities” on the Vineyard: While far less than annual in frequency, records of this species still add up to a pattern of repeated occurrence.

Wintering largely in the tropics, this species is among the earlier migrants to hit the Gulf Coast and begin its movement northward. Prothonotaries breed only up into southern New Jersey, but as these birds head toward their breeding grounds, a few individuals often “overshoot” their destination, sometimes turning up as far north as the Maritime Provinces.

A very similar pattern applies to another notable recent find, a summer tanager found out on Chappy on April 9. Like the warbler, this species is a breeding bird of the Southeast that arrives early from its tropical wintering grounds and, in moving northward, tends to forget to stop. It’s a bit more common here than the prothonotary warbler, turning up nearly annually.

Oddly, though, the existing patterns of vagrancy for these birds tend to bring them here later in the season — the second half of April and early May. Early April records, while probably not unprecedented, are unusual. Their arrival here was not associated with storm circulation or even particularly strong southerly winds, both of which can blow birds off course. Rather, these birds appeared to have been engaged in more or less “normal” migration — just ahead of schedule, and continuing farther north than usual.

While the orchard oriole is a regular Vineyard breeding bird, one found by Ken Magnuson at the head of the Lagoon on April 11 may have been the most unexpected songbird so far in April. Like the vagrants discussed above, this species winters in the tropics, arrives early in the South. But unlike the warbler and the tanager, the orchard oriole does not seem prone to overshooting, and its arrival at our latitude before the end of April is unusual.

A bit less surprising were a couple of Baltimore orioles, usually a late April arrival, seen or heard in the second week of April. Just a decade or two ago, these would have been remarkable records. But in an apparent response to a warming climate, more and more Baltimore orioles are skipping the long trip to the tropics and overwintering, or attempting to overwinter, in our region or even farther north. So these early arrivals may simply have begun their journey from a point not too far south of us.

Finally, a couple of common breeding birds that typically arrive in mid-April showed up somewhat ahead of their normal schedule. Pine warblers were found by multiple observers in the first week of April, perhaps a week ahead of their average arrival date. Chipping sparrows were likewise on the early side, with a big wave of migrants hitting our region around April 10. These are both relatively short-distance migrants, wintering as far north as they feel they can given the conditions of a particular season. Their early arrival suggests that this past season, more individuals than usual hung in close to New England through the winter.

A wide variety of birds, then, with widely varying migration strategies, have all hit the Island ahead of their expected dates. Presumably the moderate southerly winds that prevailed in early April began the push northward. And nothing about the conditions they encountered — condition of the vegetation, availability of food, or temperature — obliged them to stop before reaching our latitude.

Such early springs seem to be becoming more frequent, a response by birds to climate change and perhaps the increasing prevalence of useful resources, such as bird-feeding stations. The result is extra time for us to enjoy these seasonal residents, and, from the perspective of the birds themselves, a lengthened breeding season that may help some pairs successfully fledge their young.