Mono Lake Gulls detected on Farallon Islands!
September 4th, 2010 by Kristie Nelson
Date of sighting: late August
Hello again,
Despite a rather dismal year for Mono Lake’s California Gulls that resulted in us banding very very few this year, use of individually numbered color bands has already resulted in detections!
As of August 31, at least two juvenile Mono Lake California Gulls were detected on Southeast Farallon Island. SEFI is a small rocky island located 30 miles west of San Francisco, out in the Pacific Ocean rather near the continental shelf drop off. Last year while I stayed there, I scanned roosting flocks of California Gulls searching for ones we had color banded. They turined out to be relatively easy to find! That year, all chicks had the same color band combination, so we could not determine the number of individuals my sightings there represented.
On SEFI in fall, hundreds of California Gulls gather to roost on the island for the night. We don’t know from how far they come to roost here. Each evening, a biologist counts them as they stream in to the island after having spent the day foraging out in the open ocean. This year, I have asked the folks there to do additional daily searches for color-banded California Gulls, and thankfully they are doing so. And they are seeing them! The chicks only fledged 3-4 weeks previously! They are detecting many more color banded gulls that hatched from the south San Francisco Bay colony than Mono. The SF Bay colony had a pretty good year this year, their breeding population was larger than Mono’s (and this colony before 1980 never existed) – 500 chicks were banded in SF, vs. barely 200 at Mono (vs. 756 banded at Mono last year in the same plots that only yielded 200 this year).
With the use of individually numbered color bands, we will be able to see how long individual birds return to SEFI to roost. As of Aug. 31, they had already seen two Mono Lake California Gulls (#005 and 075). One percent of the total we banded, and I’m sure more will be seen as fall progresses. And, the area where they roost is probably about 50 acres or less. And hundreds of miles away from Mono Lake. I think we are on the cusp of discovering that a large proportion of California-born California Gulls, at least, visit Southeast Farallon Island, which is a tiny little speck considering the distance and the number of gull detections seen so far. Very exciting.
This post was submitted by Kristie Nelson.
