ML59802111

Age

Not specified

Sex

Not specified

Observation details

Id as Chapman's Swift in the field, but pictures show very short tail, and could then be just Short-tailed Swift. It was a large group of at least two species (Band-rumped and what I identified as Chapman), flying low at the end of the day chasing insects over an open field. I spent some time trying to photograph these birds, without much success... The mysterious swift had an uniform brown rump. I observed that clearly in the field against dark background, and you can see that on some pictures. I don't think it was an effect of the end of the day light. I would expect a much grayer rump for Short-tailed Swift. I usually identify Short-tailed Swift just by shape, especially the typical notch at the base of the wings. Watching these birds for about 15 min, I never saw the usual shape of Short-tailed Swift and so discarded that species. Maybe the way of flight (very fast flight, hunting at low elevation) made the shape change enough to mislead me... All these brown-rumped swifts were molting their primaries (any of the Band-rumped were). I have no idea when are supposed to molt the local Short-tailed and Chapman's.

Technical information

Model

Canon EOS 7D Mark II

Lens

EF100-400mm f/4.5-5.6L IS II USM

ISO

800

Focal length

400 mm

Flash

Flash did not fire, auto

f-stop

f/7.1

Shutter speed

1/400 sec

Dimensions

5472 pixels x 3648 pixels

Original file size

5.35 MB