ML56694731

Age

Not specified

Sex

Not specified

Observation details

At least two Chapman's Storm-Petrels came to the popcorn chum where 10 Least and 3 Black St orm-Petrels were already feeding. Small size, but noticeably bigger than Least Storm-Petrel in direct comparison (much smaller than Black Storm-Petrel). Overall size impression small and without direct comparison to Least, probably difficult to tell from that species based on size alone. What drew my attention though was the completely different flight style compared to Least: slow flight with very deep wing beats and a high upstroke; wing beats rather slow, steady and deliberate; quite the contrast with the faster, irregular, jerky flight of Least Storm-Petrel. Wing shape also different, with rounded wing tips (outer three primaries of similar length). One bird appeared to be in primary molt, with a gap somewhere around P6. Tail moderately forked; rump dark. Alf Auerbach got a photo that shows all three species present, and illustrates well the size differences. In his photo, a Leach's Storm-Petrel is on the left. Note the wide pale upper wing bands, all the way down to near the rump (photo will be added later). Howell ("Petrels, Albatrosses and Storm-Petrels of North America", 2012) notes that the dark-rumped Chapman's ssp is smaller than the usually pale-rumped Townsend's ssp of Leach's Storm-Petrel. He also notes "bounding flight with high upstroke" (which is what first drew my attention to this bird). He goes on to say that the upper wings have a "paler, brownish gray to pale buff ulnar band broadest near carpal joint and usually extending to wing bend" (the latter two field marks can be appreciated in Alf's photo). This species is a surprise here in inshore waters, as it is more commonly reported off the Continental Shelf. Both photos by Alf Auerbach. The first photo shows, left to right, Chapman's, Black and Least Storm-petrels.

Technical information

Model

DSC-HX400V

Lens

4.3-215mm f/2.8-6.3

ISO

80

Focal length

80.3 mm

Flash

Flash did not fire, auto

f-stop

f/5.6

Shutter speed

1/500 sec

Dimensions

1125 pixels x 844 pixels

Original file size

270.42 KB