As our excellent planet wraps up another orbit around its star, most naturalists probably reflect a bit on their activity over the past 12 months. In my case, this includes hundreds of hours in the field, thousands of photographs, a few notable observations, and more mistakes than I care to admit!
But I’m also thinking about what a single year doesn’t tell you, no matter how energetic you’ve been. The natural world can be wildly variable; it’s easy to miss a species entirely in a given year, and it’s equally easy to mistake a year of apparent abundance as the rule rather than the exception.
And above all, a single year gives you no information at all about long-term change, a limitation exacerbated by the present-time focus of the human mind. Whatever we’re currently seeing, we tend to assume it’s a permanent, unchanging state of affairs.
The poster child for biological change on the Vineyard is surely the tufted titmouse. This drab, grayish songbird, close cousin to the chickadee, is common across the Vineyard, and indeed across our region; a beginning birder or a new arrival might easily assume it has always been this way.
But titmice were rare in Massachusetts until about 1960, when this species (along with several others such as cardinals, Carolina wrens, mockingbirds, and red-bellied woodpeckers) began a remarkable march northward into New England. The reasons are not wholly evident, but it is generally assumed that the spread of suburban patterns of human settlement produced ideal conditions for these birds.
The semi-open habitat of a suburban yard offers the right mix of cover and foraging opportunities; fruit-bearing ornamental shrubs offer provisions deep into the winter; and increasing human interest in feeding wild birds produce a reliable food supply through the hardest part of the year.
But the titmouse, famously, bypassed the Cape and Islands as it pushed northward; the species apparently hates flying over open water, and until about 25 years ago, this bird was known here only from a handful of accidental records. In the mid-1990s, the discovery of what was obviously a titmouse-chickadee hybrid at Seven Gates tipped local birders off to the fact that at least one titmouse had set up shop here.
How the birds got here is unknown, but pure titmouse pairs were soon observed in the same area, and from that beachhead, the species expanded rapidly westward along the moraine, eastward into Vineyard Haven, and ultimately across the Island. The species is unmissable these days, and unless you know the history, you’d have no reason to suspect that titmice were ever novelties on the Vineyard.
It’s easy to add examples, each with its own story. The bald eagle, for example, was nearly driven to extinction by pesticide poisoning. Well within living memory, the species was rare in Massachusetts, and as recently as 10 or 20 years ago, a bald eagle was a notable find on the Vineyard. But as the environment gradually purged itself of DDT and related chemicals after they were banned, eagles quickly grew in numbers, and began recolonizing their former range. Today, the species is present more or less year-round on the Vineyard, and it’s no real surprise to encounter one, or even several at a time.
Change works in the other direction, as well, of course. For example, vesper sparrows bred reliably here for much of the 20th century, benefiting from an open, grassy landscape left over from the Island’s sheep-farming days. (“Formerly abundant summer resident … still common in 1934, now rare and local,” wrote Ludlow Griscom and Guy Emerson in 1959.) As oak woodlands returned, our breeding population of vesper sparrows dwindled, and finally disappeared. Today, the species occurs here only as an uncommon migrant.
The point is that while these changes are stunningly rapid in terms of the history of the species involved, they still take place over timespans that represent a good portion of a human lifetime. And they certainly don’t stand out from a single year’s data. So we either perceive them as very gradual changes, or — if we’re not paying attention over the long term — we miss them altogether, and mistake the current condition for an unchanging fact.
Changes in status may not make much difference in how enjoyable your time in the field is: Titmice are fun birds to watch, and you don’t need to know the local history of the species in order to enjoy their antics. But obviously, from a conservation perspective, these long-term trends are of great importance.
So as interesting and useful as day-to-day observations may be, any year’s records offer just a snapshot. This is why long-term monitoring projects, like the Christmas Bird Count and the Breeding Bird Survey are crucial. It’s why archival resources (like Griscom’s and Emerson’s “Birds of Martha’s Vineyard”) matter so much. And it’s why the memories of our oldest birders are worth listening to. Things change in nature. But the human perspective can be too limited to notice.
