Question about field marks for Cooper's

[gstacks]

(Today near Denver.)

I'm 97.5% sure that this is a Cooper's Hawk. Here's my question: is the white tip of the tail a good field mark to use a for Cooper's? Sibley's says that Sharpies have a narrow band of white at the end of their tail and a Cooper's has a broader one. Do you all ever use that field mark? Or is it too unreliable/hard to use?

 

[lonestranger]

If memory serves me right, the white on the tip of the tail feathers is subject to wear so it needs to be used cautiously as a field mark. I think it's one of those timely features that can be helpful if interpreted properly but is most accurate when the tail feathers are new.

Edited April 4, 2021 by lonestranger

[Tony Leukering]

15 hours ago, lonestranger said:

but is most accurate when the tail feathers are new.

Yes. Accipiter tails can wear severely, possibly due to chasing prey through veg. Molt takes place in older birds in late summer/early fall, somewhat earlier in first-cycle birds that don't breed. Some Coops have worn most of their pale tip off their tails by summer. However, a bird completely lacking a white tip is probably a SSHA, particularly before summer in the plumage cycle.

A perhaps more-reliable indicator of ID is provided by this bird's posture, with essentially straight leading edge to wings and large, jutting head. However, beware.

[Creeker]

I never use the white tip in separating the two.