A Texas trip highlight for me was watching the Cliff and Cave Swallows. Vast majority of birds we saw were Cliffs, but a few whizzed by and seemed to lack the cardinal dark throat of the former. Attempts to get flight shots buy both me and Jen were pretty futile, but I did manage so acceptable and educational ones perched.
The throat difference is pretty hard to see in the field, and most caves also seemed rustier washed on the uppers. A tricky species pair though – especially if you are watching it in a gale at the Butt of Lewis!
How long before Cave Swallow turns up in the Western Palaearctic?