MV Breeding Bird Survey Data

Martha’s Vineyard Breeding Bird Survey

The Breeding Bird Survey (BBS) is a collaborative project of the U.S. Geological Survey (USGS) and Environment Canada that enlists “community scientists” – in this case, skilled birders – to collect data for the long-term monitoring or North American breeding bird populations. About 4,100 routes, each 24.5 miles long and consisting of 50 predetermined stops, are surveyed for the BBS once each year, early in the morning during a temporal window centered on the avian breeding season. Participants spend precisely three minutes at each stop, recording all birds heard and seen within a quarter-mile radius, before moving on to the next stop. The accompanying spreadsheet presents raw data from the Martha’s Vineyard route; this information was extracted from the BBS website and will be updated as additional years of data become available.

While the numbers tallied on any given route can vary dramatically year to year due to a host of variables, the BBS project as a whole smooths out those local variations by building a huge continental data set. BBS data have proven to be a powerful and reliable way to track changes in bird abundance and distribution.

The Vineyard’s sole BBS route was established in 1996, winding from Lobsterville through Aquinnah via Lighthouse Road and Moshup Trail, along State Road to Chilmark, up the Menemsha Crossroad to North Road, east to State Road in West Tisbury, along State Road to Old County Road, south along Old County Road to the Edgartown/West Tisbury, and then east to the route’s terminus near the airport. Regular coverage of the route began in 2000; the BBS was suspended because of  COVID-19 in 2020, so no data are available for that year.

Note that this table presents all birds recorded during surveys. While most of these birds can be safely presumed to be breeders, some non-breeding birds (lingering migrants or wintering individuals) are detected most years and are included here. Also keep in mind that the number of individuals detected does not equal the number of individuals actually present: the BBS methodology was developed mainly to monitor trends by producing comparable year-to-year results, not to produce precise census numbers. Species may be under- or over-represented in the results, sometimes dramatically, depending on how detectable they are during the surveys, and many individuals and even entire species surely go undetected during the three-minute count periods.

From 2000 through 2022, the same observer — Martha’s Vineyard Atlas of Life Program Director Matt Pelikan — has covered this route, removing one potential source of inconsistency in the data (differing skill levels or sensory acuity among multiple observers). As another effort at consistency, the route is run each year, weather permitting, on the Sunday morning (to minimize interference from automobile traffic noise) closest to June 10. In reviewing or using the data we present here, though, it is important to remember that in addition to bird population size, factors such as the weather when the route is run or the date of the survey relative to the timing of the breeding season that particular year can influence the number of birds present or recorded along the survey route. Therefore, conclusions about local population trends should be drawn with extreme caution from this data set.

Still, these data give a useful and interesting picture of the Vineyard breeding avifauna, including at least a rough sense of relative abundance. And some trends, such as the well-documented regional decline in Wood Thrush numbers or the appearance and then disappearance of Indigo Bunting as a Vineyard breeding species, emerge quite clearly from these survey results. And some other apparent trends, such as a gradual increase in American Redstart numbers, may ring true to experienced Vineyard birders.