Verification of Unusual
Rec. # 2021-16
|Scientific name:||Anas diazi|
|Date:||March 5, 2021|
|Length of time observed:||25 minutes|
|Location:||Utah Lake Parkway Trail (North Shore)|
|Distance to bird:||Spotted the bird with a female mallard from 150-200m while scanning the lake through scope. I walked closer as it made its way onto the shoreline and began feeding on the mudflats. Observed at 20-25m at the closest, for about 15 minutes of total observation time.|
|Optical equipment:||10x42 Nikon Monarch Binoculars, Swarovski 20x60 spotting scope, Canon 7D w/ 100-400mm lens.|
|Weather:||Sunny, warm. Slightly hazy from pollution. 65-70 degrees. Partly Cloudy.|
|Light Conditions:||Strong glare from mid-day sun, partially backlit until I was able to get closer. Better angle improved lighting and reduced effects of heat wave.|
|Description: Size of bird:||More or less the same size as a Mallard; perhaps slightly smaller. Larger than Green-winged Teal.|
|(Description:) Basic Shape:||Dabbling Duck, Anas family.|
|(Description:) Overall Pattern:||Warm, dark-brown coloration overall with a mottled pattern across the underparts and shoulders; breast especially dark brown. Contrasting dark eye line and crown stripe, continuing vertically down the back of the neck (thinning away from crown).|
|(Description:) Bill Type:||Bright yellow bill, virtually identical to Drake Mallard.|
Field Marks and
Spent approx. 25-minutes watching the Mexican Duck in the immediate company of
three Mallards, including a female with which it seemed particularly acquainted.
While in the field, I made a considerable effort to compare the bird to online
references and field guides that I had available, such as the Macaulay and
Sibley Field Guide.
Field Marks: Bright yellow bill, suggesting male bird. Contrasting dark eye line and dark cap. Mottled, dark, warm-brown body, much darker than Mallards, but not “black.” Bluish purple speculum, same color as Mallards in lighting conditions. White borders along top and bottom edge of the speculum, although thinner and less conspicuous than that of the Mallards. The thickness of the white borders along the speculum are intermediate between Mallard and Mottled Duck, with thicker white edging than expected for Mottled and noticeably thinner edging than Mallards present. The tail is uniformly dark brown, lacking any white feathering. The tail was also flat, without any curl whatsoever.
I did not see any signs of hybridization after close scrutinization in the field (and still do not after careful review of photos). Note: Some photos do show what looks like light-colored edging on wing and/or tail feathers, which is a glare, or reflection caused by the lighting...Will include photos that show the tail at various angles.
eBird Checklist: https://ebird.org/checklist/S82820415
|Song or call & method of delivery:||NA|
|Behavior:||Feeding in phragmites/mudflats along the north shore of Utah Lake with a female Mallard and another m/f Mallard pair.|
|Habitat:||Phragmite stubble/mudflats along freshwater lake shore. Small creek inlet nearby, trickling into mudflats and flowing into lake.|
were they eliminated:
Mallard | Mallard/Mexican Duck Intergrade | Domestic Mallard: I believe the
following characteristics rule out any Mallard influence, domestic or pure:
Completely flat tail with no sign of curl. Lack of any white coloring in the
tail feathers, or anywhere else across the body, head or wings. Distinct black
central line running vertically down the nape, thickening towards the crown, and
thick dark eyeline a match for the expected plumage of MEDU. Crisp, uniform
patterning overall without any patchiness or oddity. The thickness of white on
top and bottom edge of the speculum were noticeably thinner than all other
Mallards able to be compared in flight, and matched well with comparison photos
of previously documented individuals.
Mottled Duck: Presence of relatively thick white edging along the top and bottom of speculum rules out Mottled Duck. Body color darker and colder than expected for Mottled.
this & similar species:
|Have seen Mexican Duck and intergrades on many occasions throughout the southwest, mainly in Arizona. Hundreds of Mottled Ducks most recently in Texas, July of 2020. Have never seen a Mallard.|
|References consulted:||Macaulay Library – Cornell Lab of Ornithology, Sibley Guide to Birds.|
|Description from:||NOTES TAKEN AT TIME OF SIGHTING, NOTES MADE LATER|
|Observer's address:||2622 W Dry Creek Drive, Riverton, 84065|
|Observer's e-mail address:||**|
|Other observers who independently identified this bird:|
|Date prepared:||March 6, 2021|