Date: 6/21/18 10:56 am
From: David T√łnnessen <davidtonnessenx...>
Subject: [cobirds] Peculiar Scaup Pairing
Hello Colorado birders and Ornithologists,

Here is a post I should have composed weeks ago. On June 11th of this month, at Antero Reservoir in Park County, I spent over 20 minutes observing a male Greater Scaup (unusual in Colorado in summer) paired with a female Lesser Scaup swimming around the small island on the far south corner of the reservoir. Occasionally they would participate in diving sessions that lasted a few minutes at a time, before becoming stagnant again at the surface for around the same period of time. Towards the end of my observation while I was profusely concentrated on training my phone at just the right angle so as to obtain successful "phone-scope" shots, the male scaup appeared to push the female mostly below the surface of the water so that her head was barely submerged, in what I assumed to be an event of copulation. I captured this with my phone but unfortunately it is very hard to make out.

As far as I'm aware, a pairing of this species combo or a hybrid between the two has never actually been documented (almost certainly as a result of the already quite challenging identification aspect). I would presume that any hybrid Greater x Lesser Scaup could not be safely IDed as such without requiring a capture or DNA analysis unless a parent of both species was observed present. That is why this particular pair is so significant.

While I obtained very poor quality phone-scope shots of the two ducks (focusing mainly on the male Greater since that is a very unusual species in Colorado in the middle of summer) it would be nice if someone with a larger lens than mine could venture out for more discernible documentation. So please consider fitting in an Antero Reservoir stop if you happen to be headed in that direction on Park County at some point in the next month. Photographs of the remiges in flight and head profiles would be best for ID.

Here is the eBird checklist from the observation with the best phone-scoped shots I was able to get:
Perhaps this peculiar pair will result in hybrid ducklings in the next few weeks(!)

Other notable birds present on Antero during my presence included a female Red-breasted Merganser and a Caspian Tern.

Good birding,
David Tonnessen

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