Wild Side : Downtown wildlife
When Vineyarders think of wildlife habitat, our minds gravitate to tracts of land (especially conservation land) with little or no development. But wildlife is where you find it, and given how thoroughly the human species dominates portions of Martha's Vineyard, it's worth reflecting on how the Vineyard's most densely settled areas look from the perspective of wild plants or animals.
A wide variety of resources that wildlife might use can be found in or near our town centers: landscape plantings, bird-feeding stations, vacant lots, snippets of unbuildable land. The precise mix varies depending on where you look. But in general, three rules prevail in densely settled areas. First, the land is covered by a patchwork of small and varied pieces of habitat, rather than large, unbroken tracts. Second, native vegetation has largely (though not entirely) been replaced with introduced species, in the forms of lawns, ornamentals, agricultural weeds, and invasive species such as bittersweet. And third, certain threats (predators such as cats and skunks, collision with cars and windows, even the spread of disease around feeding stations) are much more prevalent in town than in natural areas.
Predictably, wildlife varies in its tolerance of these conditions, and that tolerance determines what flourishes in a human-dominated neighborhood. It's clear, for example, that there simply isn't enough unmanaged land in a typical neighborhood for many bird species, or most of our native plants, to persist. And when you lose native plants, you also lose the insect species that depend on them. It has been depressing for me to watch the steady decline in the numbers and variety of butterflies I've been able to attract to my yard in Oak Bluffs over the last decade; development of nearby abandoned farm land, I'm convinced, has eviscerated butterfly populations in this portion of town.
Perhaps surprisingly, though, some of our breeding birds flourish in densely settled areas. Generally speaking, birds are more sensitive to habitat structure than to species mix: a thicket of exotic bittersweet, that is, works as well as a nest site as does a thicket of native greenbriar. And human-altered areas offer ample food for species equipped to find it. Robins, for instance, are prodigious harvesters of earthworms at various points in the year, and lawns (while ecologically worthless in most respects) are a fine source of this prey. Aggressively defending their nests in shrubs or thickets, pairs of "urban" robins breed successfully enough for the parents to replace themselves or even produce a surplus.
Indeed, the conditions offered by a residential neighborhood are optimal for some birds. Our two breeding species of orioles, for example - the familiar orange Baltimore and the less-known brick-red orchard - favor semi-open habitat dominated by scattered large shade trees. Because these birds spend most of their time high in tree canopies, they aren't very susceptible to threats at ground level. So a given area of an older neighborhood, such as the residential areas near downtown Vineyard Haven, supports more orioles than a comparable tract of our best native woodland.
More broadly, though, the fact that a species nests regularly doesn't mean that it reproduces successfully. The suitability for nesting of a thicket on a vacant lot may be undermined by effects spilling in from nearby houses. Roaming housecats, for example, undoubtedly kill a high percentage of fledglings in settled areas, especially affecting birds that nest close to the ground. The subject has never been studied on the Vineyard, but my impression is that many species of birds nesting in our neighborhoods experience too much mortality for their local populations to be sustainable.
There is even a sense in which wildlife that flourishes in a town center can have negative value. European starlings, for example, are positively encouraged by human settlement. They nest in our attics, flock to feeding stations, devour the fruits of landscape plants, and are astonishingly deft at eating grubs out of lawns. They also eat the eggs of smaller birds, displace native woodpeckers, nuthatches, and chickadees from potential nest sites, and out-compete smaller birds for rich sources of food. By encouraging this exotic bird, a residential neighborhood produces negative ecological effects that radiate out as far as the starlings themselves wander during the course of a year.
So there is no simple answer to the question of how well-settled areas work for wildlife. In general, diversity is lower than in natural areas, and a small number of generalist species often dominate; some of the most successful species are also, regrettably, destructive ones. Yet more wildlife persists in settled areas than the casual observer might expect; whether local breeders, migrants from off-Island, or overflow from populations in natural areas, the Vineyard's "urban" wildlife displays surprising variety and resilience. And the habits and adaptations of these species amply reward careful study.