April 27, 2004
Summary of 2003 Martha’s Vineyard Christmas Bird Count
December 28, 2003
Count Code MAMV
There are numerous items that make the 2003 Martha’s Vineyard Christmas Bird Count very unique, including the weather, a record number of species observed, including three unusual species, an invasion of migrating common redpolls, and that slightly more than one quarter of the species observed set new highs (for all counts since 1960).
First, the weather was ideal for the second consecutive year. We had unseasonably warm temperatures, with a high of 50oF and virtually no wind. There was no sign of weather that would make birds hide deep within thickets and the seas were flat calm.
This ideal weather undoubtedly contributed to our finding 130 species on Count Day, a new record for the Vineyard Count. Although I have not yet computerized the various measures of effort for our Count, I believe our effort was slightly lower than in the past several years because one of our regular territories received only partial coverage this year.
I have flagged three unusual species: long-eared owl, Bohemian waxwing, and clay-colored sparrow. The following supports these three sightings.
· The long-eared owl is unusual since it has not been seen on a Vineyard count since 1992. And this year two different owls were found (heard calling), one off North Road in Chilmark and one on West Chop Vineyard Haven.
· The second ever Bohemian waxwing was found by Frank Gallo and Lanny McDowell –this individual was observed twice in a flock of cedar waxwings less than 100 feet away – the closest observation was from underneath while it was perched on a telephone wire, so its rufous undertail coverts were plainly visible.
· The third unusual species is the clay-colored sparrow that was observed by Matt Pelikan under ideal lighting and at a distance of only ten feet. It was in a flock of field sparrows and “… it was a textbook clay-colored sparrow.” This individual was not observed again.
Common redpolls were truly amazing! This winter eruption of redpolls shows all the characteristics of fall migration on the Island, with migrants arriving from the south off the Atlantic Ocean at dawn (having flown past the Island at night), small flocks across the Island (10 of 13 field teams reported redpolls) and with flocks of redpolls leaving the island’s western tip. At dawn on the southeast corner of the Vineyard I (Robert Culbert) observed 2 separate flocks of about 20 individuals each (and one flock of 10 white-winged crossbills) arriving on island from the south (over the Ocean); these flocks immediately landed in the pitch pines and began foraging voraciously with pieces of pine cones raining down from the trees. Also spectacular was the dawn movement of redpolls from the western end of the Island, where over 500 individuals were observed leaving the Vineyard heading to the northwest and the mainland (about 10 miles away across Nantucket Sound and Buzzard’s Bay). These observations are characteristic patterns of southward migration during the fall on the Island.
Finally, one quarter of the species observed on the Count (33 species) set new highs for number of individuals observed on the Count. And the increases were substantial, ranging from about 3% (Carolina wren) to almost 3000% (common redpoll). The percent increases are documented in the following table, showing the high counts from 1960-2002, the new high counts established this year, and the percent increase for that species.
Species setting new highs on the 2003 Martha’s Vineyard Count.
Several comments concerning this chart are in order.
· Species living on land were more likely to set new highs than birds living on the water (80% of the species in this chart are landbirds while only 60% of the species observed on this year’s count were landbirds).
· I do not believe that increased effort is responsible for these increases because this year’s effort was not higher than in past years.
· While the conditions for viewing and counting all birds were ideal, I do not believe that weather alone can account for all the observed increases since we have had other count days with ideal weather (most recently 2002).
Therefore, I believe that populations of some (but not all) of these species are higher this year than they have been in the past. A detailed analysis of the 44 consecutive years of data from Martha’s Vineyard should be able to separate the effects of effort to reveal population trends on the Island.