This post is going to be brief cause I have to keep working on grant proposals to keep this research going... the results of our post-breeding tern chasing work are getting more and more interesting. (We and collaborators spent thousands of hours from late July - late September counting flocks and identifying individually banded roseate terns their "staging period" when they're resting and feeding in preparation for flight to South America).
Ben Carroll photo. Flock of roseate and common terns, Wood End flats, Provincetown, Sept 21, 2009.
So, although it will take many months for us to compile over 20,000 observations of colorbanded adult roseates from 11 observers... we were happily surprised to find some very interesting things, just from compiling our incidental observations of metal-banded fledglings. Some of the young terns that were produced on the breeding islands this year are given two metal bands, one of which is so-called "field readable" with a unique four-character combination of numbers and letters etched into the metal. With a good scope, good light, and close proximity to the flock, you can read these bands and figure out which breeding colony that tern came from (along with at least one adult still feeding it).
The exciting thing is, without even really focusing on this task, we made 760 observations of 422 individual fledglings, 13 of which were actually color-banded. More on those anomolies in a moment. Turns out we saw about 15% of the fledglings that were banded this year, coming from eight breeding colonies (from Great Gull, NY all the way to Country Island, Nova Scotia!)... we saw fledglings from any colony that banded more than five individuals! This gives even more weight to the notion that almost the entire population of northeastern roseate terns (there are about 6,000 total breeding birds in the population) come to the greater Cape Cod region to rest and feed before migrating to South America!
Fledgling roseate tern and colorbanded adult, Popponesset Spit. John Van de Graaff photo.
And the even more exciting finding... those colorbanded roseate chicks. Due to some short-term banding for purposes of estimating productivity, 14 roseate tern chicks got a combination of a single colorband and metal band or two colorbands at their breeding colony of about 24 pairs on Country Island, Nova Scotia. The Canadian Wildlife Service (CWS) intended to catch the chicks and remove the bands, but they weren't able to find them due to dense vegetation. When colorbanded fledglings started showing up on Cape Cod beaches, we were initially confused... but then tracked down the source and were thrilled to let CWS know that we had spotted 13 out 14 of their colorbanded fledglings (93%)!!
We tripled their productivity estimate, AND learned a lot about where roseate terns go after they leave the breeding colonies. Some of these fledglings stuck to one staging beach for weeks on end, while others (with parent(s)) moved from beach to beach, staying in the region anywhere from one to 38 days. Exciting stuff! And more to come... also check out old posts for some more info and photos of masses of terns...