Wild Side: Killdeer plovers

These cold-tolerant shorebirds can be spotted year-round.

Killdeer plovers favor open pastures or the shoreline of ponds. — Grayson Smith/USFWS

Three species of so-called “banded plovers” occur regularly on Martha’s Vineyard. Of these, the piping plover, an intensively managed species that nests in modest numbers on our beaches, gets all the press. And the semipalmated plover, a boreal breeder that occurs here as a common migrant, is most often seen.

But it is the third species, the killdeer, that’s on my mind. Nesting here in small numbers (locally, it is less numerous than the federally threatened piping plover), the killdeer is one of our earliest arrivals each spring. Mid-March through April sees the noisy return of this species, giving its ringing call overhead as it explores the Island.

All three banded plovers are in the same genus, Charadrius. Accordingly, they resemble each other in overall pattern (brown or gray above, white beneath, and marked in at least some of their plumages by bold black striping across the breast). And some aspects of their behavior are similar, as well. Their breeding displays, for example, involve prolonged flights with repetitive calls by the male.

But while the piping and semipalmated plovers are both birds of the oceanic shoreline when they’re here, the killdeer associates more with fresh or brackish water and, indeed, does just fine with no water around at all. And the killdeer is significantly larger than its relatives, roughly robin-sized with a long tail.

While I’m sure the Vineyard is visited by truly transient killdeer in the spring, spring migration for the species seems to consist mainly of the arrival of breeders. (This is true of most birds; on the way to their nesting grounds, migrants tend to take the most direct route possible, and hence the Vineyard is largely bypassed during spring migration.)

Killdeer are much more common in the fall, sometimes showing up in groups of a dozen or so on mud flats, well-grazed pastures, or other flat, open habitats. The species is surprisingly cold-tolerant for a shorebird, which as a group tends to engage in long-range migration to contrive a perpetual summer. Killdeer are recorded on the Vineyard’s Christmas Bird Count with some regularity and, in mild seasons, may linger deep into or even through the winter. The fields around the Agricultural Hall in West Tisbury, for some reason, seem to attract this species if it is present in winter.

For nesting, the killdeer favors large, open areas with low vegetation, or, better still, no vegetation at all. They will nest on farm fields, well-grazed pastures, or on the shores of drawn-down great ponds. Needing a scant month from nest-building to dispersal of the young, which are mobile almost from the moment of hatching, killdeer can nest successfully in transient habitats.

Elsewhere, the species has been observed nesting in some surprising places: On flat rooftops, for example, and at least once, according to historical accounts, between the ties of a railway that was in active use. Because of their habitat preferences, most or all of our nesting killdeer occupy sites along the south shore of the Island. Insects, studies have shown, constitute virtually 100 percent of a killdeer’s diet.

I don’t have a strong sense of how many pairs of killdeer the Vineyard supports, but the number cannot be great — a dozen? Two dozen? This relatively low density is not surprising for the species. But the killdeer has a vast geographical breeding range that encompasses most of temperate North America, and even at low densities, that range translates into a lot of birds. One estimate pegs the continental population at about two million, with the bulk of these birds nesting in Canada. The species has been plagued by overhunting, insecticide impacts, and the loss or modification of farmland, and its numbers declined quite sharply during the latter half of the 20th century. There are some indications that the trend has reversed.

Once a male has staked out a claim and attracted a mate with his courtship displays, the female killdeer lays four eggs, rarely more or fewer, in the simplest possible nest: a shallow scrape, usually decorated with stones or other debris. In this, the species resembles the related piping plover. Both species give a “broken wing” display when they feel their eggs are threatened: One or both of the adult birds crawl pitifully across the ground, dragging a wing, calling, and in the case of the killdeer, flashing a rusty top surface of the tail, to lure the intruder away from the nest.

This is your signal to leave. Plover eggs are exquisitely camouflaged and appallingly easy to step on. My advice is to follow the displaying adult, which knows where the nest is and where it wants you to go. Leaving as quickly and carefully as possible is your unambiguous legal and ethical obligation in the case of piping plovers, protected under endangered species laws. Killdeer, protected by the somewhat less stringent terms of the Migratory Bird Treaty Act, also deserve to be disturbed as little as possible.

You’re welcome, though, to watch from a distance the birds themselves deem comfortable. An active, intelligent species with complex behavior, the killdeer is an underappreciated gem of the Vineyard avifauna.