--_000_8A132C4E1B45CF4C9F8F778D6624907A25A53DC9mb03aggiesusued_
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
As Craig mentioned, I quickly went out to Logan's First Dam to study the mystery duck he reported earlier today. I believe it is a Mexican Duck, a.k.a., Mexican Mallard.
The very definition of a Mexican Duck is still subject to controversy. Currently the American Birding Association considers it a subspecies of Mallard, largely based on reports of extensive hybridization with Mallards in the 1970s. But several different recent investigations in the genetics of ducks have shown Mexican Ducks to be most closely related to Mottled Ducks, and they are also more closely related to American Black Ducks and even Eastern Spot-billed Ducks than they are to Mallards.
The extent of hybridization with Mallards is also subject to controversy. David Sibley has said that "virtually no pure Mexican [Ducks] occur in North America." Others have said that hybridization is very rare. The picture is certainly complicated by natural clines in the species, with more northern individuals having more in common with Mallards than more southern individuals. It is difficult to know whether this increase in Mallard-like traits in the northern part of the range reflects extensive hybridization, clinal variation in a species that rarely hybridizes, or some combination of hybridization and inherent variation within a "good" species. Here are two good recent summaries that come to very different conclusions:
http://www.azfo.org/journal/volumes/Volume2-3.pdf
http://www.sibleyguides.com/2011/05/intergradation-between-mexican-duck-and-mallard-in-arizona/
With regards to the duck seen today in Logan, I believe it is close to a pure Mexican Duck, if such a thing exists. It is an adult male, which greatly simplifies things. There are a few traits that are somewhat Mallard-like, but I don't know how variable these traits are within pure Mexican Ducks. At certain angles, a slight green sheen can be detected in a small part of the top of the crown. The central retrix (tail feather) curls up just slightly, not looping around like that of a Mallard's, but lifting just subtly off the plane of the other tail feathers. Otherwise, the duck looks to me like a pure Mexican Duck. The tail is very dark, with no white patches (compare Sibley's photo of a "Male Mallard close to Mexican-type" in the link above. The rump seems concolor with the back and flanks in most shots, not noticeably darker. (It does look darker in one or two photos, but I believe this is an effect of shading from the wingtips. When directly illuminated, it does not look darker.) The white at the front and back of the speculum is rather limited, although it would be nice to see a photograph of the full spread wing. (To clarify, Craig's email implied that this bird had no white and was therefore an American Black Duck. To the contrary, this bird does have some white in the speculum, and that it is therefore NOT a Black Duck.)
Here is a link to an album of my photographs of this bird on Flickr:
http://www.flickr.com/photos/tsirtalis/sets/72157629191690717/
Good birding,
Ryan
Ryan P. O'Donnell
Logan, UT
--_000_8A132C4E1B45CF4C9F8F778D6624907A25A53DC9mb03aggiesusued_
Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<html dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css" id="owaParaStyle"></style>
</head>
<body fpstyle="1" ocsi="0">
<div style="direction: ltr;font-family: Times New Roman;color: #000000;font-size: 12pt;">
As Craig mentioned, I quickly went out to Logan's First Dam to study the mystery duck he reported earlier today. I believe it is a Mexican Duck, a.k.a., Mexican Mallard. <br>
<div><br>
</div>
<div>The very definition of a Mexican Duck is still subject to controversy. Currently the American Birding Association considers it a subspecies of Mallard, largely based on reports of extensive hybridization with Mallards in the 1970s. But several different
r<font class="Apple-style-span" size="3">ecent investigations in the genetics of ducks have shown Mexican Ducks to be most closely related to Mottled Ducks, and they are also more closely related to American Black Ducks and even Eastern Spot-billed Ducks than
they are to Mallards. </font></div>
<div><font class="Apple-style-span" size="3"><br>
</font></div>
<div><font class="Apple-style-span" size="3">The extent of hybridization with Mallards is also subject to controversy. David Sibley has said that "virtually no pure Mexican [Ducks] occur in North America." Others have said that hybridization is very rare.
The picture is certainly complicated by natural clines in the species, with more northern individuals having more in common with Mallards than more southern individuals. It is difficult to know whether this increase in Mallard-like traits in the northern
part of the range reflects extensive hybridization, clinal variation in a species that rarely hybridizes, or some combination of hybridization and inherent variation within a "good" species. Here are two good recent summaries that come to very different conclusions:</font></div>
<div><font class="Apple-style-span" size="3"><br>
</font></div>
<div><font class="Apple-style-span" face="Tahoma" size="2"><a href="http://www.azfo.org/journal/volumes/Volume2-3.pdf" target="_blank">http://www.azfo.org/journal/volumes/Volume2-3.pdf</a></font></div>
<div><a href="http://www.sibleyguides.com/2011/05/intergradation-between-mexican-duck-and-mallard-in-arizona/" target="_blank">http://www.sibleyguides.com/2011/05/intergradation-between-mexican-duck-and-mallard-in-arizona/</a></div>
<div><br>
</div>
<div>With regards to the duck seen today in Logan, I believe it is close to a pure Mexican Duck, if such a thing exists. It is an adult male, which greatly simplifies things. There are a few traits that are somewhat Mallard-like, but I don't know how variable
these traits are within pure Mexican Ducks. At certain angles, a slight green sheen can be detected in a small part of the top of the crown. The central retrix (tail feather) curls up just slightly, not looping around like that of a Mallard's, but lifting
just subtly off the plane of the other tail feathers. Otherwise, the duck looks to me like a pure Mexican Duck. The tail is very dark, with no white patches (compare Sibley's photo of a "Male Mallard close to Mexican-type" in the link above. The rump seems
concolor with the back and flanks in most shots, not noticeably darker. (It does look darker in one or two photos, but I believe this is an effect of shading from the wingtips. When directly illuminated, it does not look darker.) The white at the front
and back of the speculum is rather limited, although it would be nice to see a photograph of the full spread wing. (To clarify, Craig's email implied that this bird had no white and was therefore an American Black Duck. To the contrary, this bird does have
some white in the speculum, and that it is therefore NOT a Black Duck.)</div>
<div><br>
</div>
<div>Here is a link to an album of my photographs of this bird on Flickr:</div>
<div><a href="http://www.flickr.com/photos/tsirtalis/sets/72157629191690717/" target="_blank">http://www.flickr.com/photos/tsirtalis/sets/72157629191690717/</a></div>
<div><br>
</div>
<div>Good birding,</div>
<div>Ryan</div>
<div><br>
</div>
<div>
<div>
<div style="font-family: Tahoma; font-size: small; "><font size="3" face="Times New Roman">Ryan P. O'Donnell</font></div>
<div><font class="Apple-style-span" size="3">Logan, UT</font></div>
</div>
</div>
</div>
</body>
</html>
--_000_8A132C4E1B45CF4C9F8F778D6624907A25A53DC9mb03aggiesusued_--
