ML129482661

Age

Not specified

Sex

Not specified

Observation details

Seen both at rest and in flight at about 50 to 100 meters in bright sunlight, sidelit. The bird was mainly perched on the mud near the shoreline and preening occasionally, and then took off on a short foraging flight near shore, with several plunge dives, before eventually flying south and west across the lake. Total observation time about ten minutes. This was a Sterna tern with pale upperparts, a prominent dark carpal bar, short reddish legs and a moderately-sized red bill with a dark tip. There was a black cap with a white forehead. In flight, the upperwings were rather uniformly pale gray-white, a bit like Forster's Tern - I did not detect any dark wedges or significant black color (although one of the photos showing the bird in the act of stretching shows a hint of dark markings on the upper surface of the primaries - see below). The underwings had a moderately thick triangular black line outlining the primaries on all sides, but not extending to the inner wing. The tail was whitish and slightly forked, but without long streamers. I failed to note the relative position of the wingtips and tail at rest. I did not notice any prominent contrast between the tail center and sides or between the tail, rump or back in flight, all appearing pale gray to white. I took a number of digiscoped photos, but the distance and heat haze limited their quality significantly. Based on the structure, leg and bill color, I am confident this was a Sterna sp. tern. The prominent dark carpal bar essentially rules out Forster's, and the short reddish legs also argue against that species, which I am very familiar with. Arctic Tern would be very unlikely here, and the moderately thick and prominent black markings on the undersurface of the primaries in flight argues against that species, with which I have limited familiarity from California pelagic trips. Although the pale and uniform uppersurface of the wing in flight seems atypical for Common Tern, this seems to be the best fit. I've tentatively aged the bird as immature based on the carpal bar - although adults in basic plumage can apparently have a carpal bar, this plumage is not usually seen in the US, I believe.

Technical information

Model

COOLPIX S9300

ISO

125

Focal length

16.5 mm

Flash

Flash did not fire, auto

f-stop

f/5.6

Shutter speed

1/200 sec

Dimensions

757 pixels x 609 pixels

Original file size

106.42 KB