On Mexican Ducks and the notion that not every bird is identifiable

[Peter Burke]

COBirders,

A bit of armchair birding on my part. There have been several migrant waterfowl reported in Boulder County this weekend. In addition, a male Mexican Duck has been reported at Hecla Lake in Lafayette. I'm not sure if a Mexican Duck is considered to be a migrant, vagrant or resident in Northern Colorado in November, but it's a good bird in any respect.

While I've yet to see this bird in person, I've seen some excellent photos on eBird. There has been quite a bit of chatter regarding the slightly curled tail feathers (upper tail coverts), which I've often heard are evidence of Mallard genes. A little bit of Googling revealed several excellent articles on the topic, among them: a 2012 essay in Colorado Birds by Tony Leukering and Steve Mlodinow arguing for full species status for Mexican Duck. (The AOS split Mallard and Mexican Duck in 2020.) Jack Bushong wrote a thorough article on the field identification of Mexican Ducks for the ABA website, which also has a terrific photo essay by Steve Mlodinow. Steve argues that "pure" Mexican Ducks can exhibit Mallard-like features, like the curly tail feathers.

So how comfortable can we be in identifying Mexican Ducks in Northern Colorado? I'd be interested to learn what others have to say on this topic. But one thing is certain -- we should all brush up on the differences between these two species and make an effort to document sightings in eBird, particularly with photos, keeping in mind that selecting "Mallard/Mexican Duck" is a good option when one is not certain.

If the links embedded in the post don't work, here are the URLs:

Leukering/Mlodinow - http://web.corral.tacc.utexas.edu/UAF/arctos/mediaUploads/demboski/In_the_Scope_CB_October_2012.pdf

Bushong - https://www.aba.org/mexican-duck/

Mlodinow - https://www.aba.org/mexican-duck-photo-essay/

Good birding,

Peter Burke

Managing Editor, Colorado Birds

edi...@cobirds.org