Wild Side: Counting birds

Breeding Bird Survey results.

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The view from stop No. 2 on my route, at Lobsterville, Aquinnah. — Matt Pelikan

While I enjoy birding under any circumstances, I’m especially fond of “citizen science” birding: participating in projects or events that use amateur observers to generate data for scientific analysis. The Christmas Bird Count (CBC) may be the best-known example, a continent-wide annual event that puts thousands of observers into the field to census early winter birds. The late spring counterpart of the CBC is the Breeding Bird Survey (BBS), coordinated by the U.S. Geological Survey and consisting on a continent-spanning panoply of more than 4,600 routes in the U.S. and Canada.

Like all these routes, the Martha’s Vineyard survey that I conduct consists of 50 predetermined stops spaced a half-mile apart. Starting a half-hour before sunrise during a specified window in late spring or early summer, observers spend exactly three minutes at each stop, recording every bird heard or seen within a specified radius. Results from all these surveys are combined into one large data set, which over time can vividly illustrate changes in the abundance or distribution of breeding birds.

Set up years ago by Vern Laux, the Vineyard route passes through some of the best bird habitat on the Island. Up-Island portions in particular offer fun birding, from Lobsterville, along Lighthouse Road and Moshup Trail, and then along State Road into Chilmark. Later portions, including Old County Road in West Tisbury and a portion of the Edgartown–West Tisbury Road, are less fun, with drier, less varied habitat. Traffic, too, is a concern for the final half of the route; I run it on a Sunday morning if possible, but even so, more than 20 cars may pass during a three-minute stop, smothering the sound of any birdsong.

Part of the appeal of covering a BBS route certainly resides in the scientific purpose of the project; it’s satisfying gathering data that you know will be useful for bird study and conservation. But the project offers me more personal satisfaction, as well; in effect, a BBS survey is a four-hour crash course in what birds are around, and, as years go by, it’s a fascinating opportunity to experience the changes — sometimes abrupt, sometimes gradual — that are always going on in the Island’s bird life. As always, this year’s survey produced a lot to ponder.

First, regular readers may recall the “Wild Side” column that ran on May 15 (bit.ly/WildSideOvershoot), summarizing an unusual influx of rare or unseasonably early avian arrivals in late April and early May. Dominating that influx were indigo buntings, reported in numbers the Island hasn’t seen in many years. Recalling a similar event back around 2003, in which some of an early spring flight of buntings remained to establish a modest breeding population on the Vineyard, I speculated that this year’s influx might have a similar outcome.

If it did, it was not detectable on Sunday’s survey. All 50 stops were bunting-free, and I didn’t hear any singing, either, as I drove, car windows down, between stops. This doesn’t mean that the species has not resumed nesting here; they could be in places not sampled by my BBS route, and even along the route, the relatively short sampling period at each stop makes it very possible to miss an uncommon local breeder.

Arguably the most interesting find during my 2019 survey was, unfortunately, a casualty: I found a freshly road-killed American woodcock lying on the pavement near one of my stops along Moshup Trail. Still warm, the bird had probably been killed an hour or less before I passed by. For some reason, woodcock seem to be prone to collisions with cars; I find at least one or two every year, which seems like a disproportionate toll for a species that is not terribly common here. Something — either a food source of some kind or perhaps the combination of vegetation adjacent to completely open space on a roadside — must attract them to this hazardous location, and then when an oncoming vehicle startles them, they fly into its path. (And no, I couldn’t count the woodcock; birds must be alive to be counted!)

Other surprises included the number of willow flycatchers and yellow-billed cuckoos I counted (two in each case); while both species probably breed annually on the Vineyard, they’re scarce, and neither one is a sure thing on my route. The numbers, in this case, probably don’t say anything significant about the status of either species. But since I don’t see these birds often, it was fun to pause briefly and watch them do their thing.

On the downside, I was surprised not to encounter any wood thrushes at all. Again, one can’t conclude much based on one year’s data; assuming a species is present but uncommon, minor differences in blind luck can make the difference between finding none and finding several. But the number of wood thrushes I’ve picked up on the BBS seems to be creeping slowly but inexorably downward. Whether this reflects unfavorable changes in wood thrush habitat on the Vineyard, or equally harmful changes in the tropical habitats where our wood thrushes winter, I suspect this species is in trouble on the Island.