Could you explain why this bird should be a hybrid ?

To my eyes this bird looks like Red-winged Pratincole. The areas of red at the base of the bill are right on the spot for Red-winged (too much for Black-winged), and the coverts are the typical muddy brown of red-winged, contrasting well to darker flight feathers.

Dear Henrik!

Sorry for the late answer, but I was in Belarus and just now arrived.

I'm not an excellent Black-winged Pratincole observer. I have been seen only 7-8x.

That's bird strange for me, because more red on the bill ( other birds were less red at the bill base). Tail was a sligthly longer, than on the pure birds. Tail was equal long as the wingend.

Just few times breeding pure Black-winged pair in Hungary, often hybridization the both pratincoles.

Best Regards

Andras

P.S.: Klaus! This bird has pure black underwing color!