Wednesday 16 December 2015

Western Meadowlark x Eastern Meadowlark

presumed Western Meadowlark x Eastern Meadowlark hybrid, Lower Latham Reservoir, Weld County (Colorado, USA), 21st March 2016 - copyright Steve Mlodinow
(photo ID: 2770)

Steve wites:
"This bird was making a continuous burbling noise (not the flight song of Western Meadowlark) that doesn't fit either species, though I gather can be given by either.  The call was much like that of a Western Meadowlark.

The very black and white head and nape striping is rather unusual for Western Meadowlarkas is the dark center to the one fully visible greater wing-covert and the rust-tinged black bordered tertial.  Excepting confluenta, the subspecies from the Pacific NW, those features are rather atypical for Western Meadowlark.  However, these features are all typical for Eastern Meadowlark.  The yellow malar extent is definitely more Western Meadowlark-like.

These photos were shared with 3 excellent and well-respected field-ornithologists. One said "Eastern Meadowlark" even after examining specimens, another said "Western Meadowlark", and perhaps the wisest, said "ugh!"

Since ~1% of meadowlarks at the zone of contact are hybrids, and we are not far from said zone of contact, occasional hybrids in Colorado are not unexpected.

presumed Western Meadowlark x Eastern Meadowlark hybrid (same bird as in photo ID 2770 above), Lower Latham Reservoir, Weld County (Colorado, USA), 21st March 2016 - copyright Steve Mlodinow
(photo IDs: 2771-2772)

Steve photographed the next bird, a juvenile (or juvenile transitioning to first-winter plumage), in an area where nominate Eastern Meadowlarks used to breed.  He says,
"This bird's tail appeared totally white on the outer 3 tail feathers (r6 is outermost, so r6 thru r4) and there is a substantial amount of white on r3.  This tail pattern is more consistent with Eastern Meadowlark, but probably is within the realm of possibility for Western Meadowlark.  The central tail feathers are barred brown without any dark brown along the shaft, which is consistent with Western Meadowlark (or Lilian's Eastern).  The dark post-ocular stripe is dark and equal in darkness to the lateral crown stripe.  From what I can tell from specimens, juvenile Western Meadowlark should have a paler and more diffuse post-ocular stripe.  This combination of features is intermediate between those of Eastern Meadowlark and Western Meadowlark and would seem to suggest Eastern Meadowlark x Western Meadowlark.  Molt-timing apparently eliminates juvenile Lilian's.

apparent Western Meadowlark x Eastern Meadowlark hybrid, Logan side of Jumbo Reservoir, Logan County (Colorado, USA), 14th August 2015 - copyright Steve Mlodinow
(photo IDs: 2301-2303)

Western Meadowlark Sturnella neglecta
Eastern Meadowlark Sturnella magna
Lilian's Meadowlark Sturnella magna lilianae

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