The Black-browed Reed Warbler that wasn't

By Abhijit Menon-Sen <ams@toroid.org>

2015-11-10

I am a big fan of written descriptions of field sightings.

Forcing myself to write down my observations and present them in an organised manner has helped me to learn to make better use of however little time I get with a bird in the field. Unless I did this consciously, it was all too easy to spend time looking at birds without seeing very much.

Written descriptions are not always reliable, and the reliable ones not always conclusive. A photograph, regardless of the quality, can often serve to clear up an incomplete description; but photographs can't be the beginning and end of identification, because they come with their own problems.

Here's an old thread from delhibirdpix that shows how photographs can mislead even a succession of expert observers. The ingredients were all in place: a location that has an extraordinary (and well-deserved) reputation for being a vagrant-trap, a small warbler with an unmistakable black brow, and only one species anywhere in the region matching that description.

Mystery warbler

But two and two did not add up to Black-browed Reed Warbler in this case. The identification hinged entirely on the black brow, which turned out to be an artifact introduced while lightening a dark photograph, as shown in the comparison above. The bird was (probably) a Booted Warbler with an entirely unremarkable pale brow.

Here's another post (from about the same time) about a similar problem.