Gull-billed Tern (Gelochelidon
nilotica vanrossemi)
San Mateo County, California
Digiscoped with Panasonic DMC-LZ5 | Nikon FieldScope 3 | 30X WA | hand-held
(no adapter).
After learning that a Gull-billed Tern first seen yesterday was back at Redwood Shores, Robbie Fischer and I decided to look for it. When we arrived, about a dozen other birders were viewing the bird through spotting scopes. The bird was sitting on a small islet at the south end of the pond at the end of the road. Click here for map.
Most records of northward dispersal of Gull-billed Tern in California have been in May/June (two Santa Barbara County records, two of the three Los Angeles County records and one probable Ventura County record). Apart from a few spring/summer birds at Bolsa Chica and other coastal Orange County localities in recent years, that is about all the records there are for northerly dispersal in California. It is likely that this is the same individual seen and photographed by Mike Danzenbaker at Palo Alto, Santa Clara County on 3 May 2009. Distant photos were obtained of that bird.
There is a sight record for Sacramento County that some people think is correct but I have not seen the details if they exist. Gull-billed numbers in San Diego Bay have increased since they first colonized that area in 1985, with current numbers at about 50 pairs; but that remains the only coastal nesting site (fide Kimball Garrett).
Otherwise, in California, this species is known to breed only at the Salton Sea where about 100 pairs nest. Gull-billed Tern is a "California Species of Special Concern:"
http://www.nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=10400
The subspecies G. r. vanrossemi is based on specimens from the Salton Sea. The validity of this race has
been disputed, but it is recognized as valid by Clements and BNA. It is said to be larger than G. r. aranea
which replaces it on the East Coast of North America, but has a shorter tail and thicker bill. Four other subspecies
are recognized around the world differing slightly in measurements.
Danzenbaker photos from 3 May 2009:
http://www.avesphoto.com/SBB/TRN-20090503_MD_5927.jpg
http://www.avesphoto.com/SBB/TRN-20090503_MD_5928.jpg
http://www.avesphoto.com/SBB/TRN-20090503_MD_5935.jpg
http://www.avesphoto.com/SBB/TRN-20090503_MD_5936.jpg
Updates
A flight shot by Kris Olsen is here.
Additional photos by Kris Olsen are here.