Spring's on the way – birdsongs tell us so
For me, the most enjoyable sign of spring's approach is the gradual resurgence of birdsong on the Vineyard. One by one, our resident species are tuning up and contributing their tunes. And before long, the earliest migrant songbirds will arrive to add their voices.
Having paid close attention to birdsong for years, I've found that many species are quite regular about the date on which they resume song in late winter. The middle of February invariably brings the first music from one of my favorite species, the song sparrow.
Accordingly, on Friday, February 11, I stepped out onto our front porch and heard the seasonal debut of this species from the thicket across the street.
There is nothing fancy about this species, which, like most sparrows, is a utilitarian, streaky brown above and white beneath. Distinctive on a song sparrow is the pattern of black markings on the breast: an array of short streaks surrounding a pronounced central spot. Even so, sparrows are confusing, and even serious birders are sometimes taxed to decide if a particular bird is merely a song sparrow or one of several less common look-alikes.
They aren't, however, called song sparrows for nothing, and the remarkable song of this species sounds nothing at all like the song of any other sparrow likely to be heard singing here. A highly variable mix of trills, buzzes, and piping notes, the song of this aptly named sparrow is loud, persistent, and, by the time spring has fully sprung, almost inescapable on the Vineyard. And it is highly unusual in the world of birdsong.
The songs of most of our songbirds are relatively constant among individuals of a species, with a distinctive tone quality and pattern of notes. If you've heard one yellow warbler's sibilant "Sweet, sweet, sweet, I am so sweet," you've heard them all, and indeed you will be able to recognize the pattern sung by this species anywhere within its wide geographical range. Not so with the song sparrow: each member of this species learns a unique mix of about a half-dozen song types, which may have no obvious resemblance to each other, or to the songs that other song sparrows are singing.
This variability raises the question of how to recognize a song sparrow song (or, for that matter, how song sparrows recognize each other). I can't speak for the sparrows, but for humans, some help comes from the fact that building blocks of song sparrow songs always show some consistency. Clear notes, trills, and buzzes come in different sequences, at different pitches.
But it often sounds like song sparrows are assembling personal songs from the elements of a common vocabulary. Also, the tones and intervals used by a song sparrow often fit closely to standard human musical scales, helping us recognize the species and often making it possible to learn the songs of a particular sparrow. (The bird that began singing last Friday, I feel confident, was the same male that bred in the thicket last summer.) Research has shown that song sparrows learn their song repertoire early in life and keep it, unchanged, for the rest of their lives (typically about three years, sometimes as much as nine).
The song sparrow is one of a dozen or so songbirds that I consider truly abundant, not merely common, on the Vineyard. Extrapolating from the 35 or so I find most years on a Breeding Bird Survey route I'm responsible for, I estimate our breeding population at perhaps 1,500 birds. Many leave for the winter; some, like my friend across the street, remain, joined by large numbers of migrants from farther north. The Vineyard Christmas Bird Count sometimes tallies more than 500 song sparrows; allowing for the many birds that survey misses, this species may be more numerous here in winter than in summer.
Part of the success of this species is attributable to its tolerance of a wide range of habitat types. Song sparrows are probably happiest nesting in the shrubby margin of a freshwater wetland. But they also nest in dry woodland edges, in clumps of shrubs on grassland, and even in densely settled areas (several pairs typically nest in yards within a block of Main Street in Vineyard Haven). Song sparrows, with a tendency to nest on or near the ground, suffer high rates of nest predation by cats, skunks, and raccoons. But the species is prolific, with two broods in a season seeming to be the rule and not the exception on the Vineyard.
A familiar sight both at feeding stations and in the wildest parts of the Island, song sparrows rank among the most versatile breeding bird on the Vineyard. And their physical and psychological ability to create individualized song is unique among the birds Islanders get to hear.