Plegadis Ibis hybrids in Oklahoma
On 30 May 2002, Arterburn birded the Great Salt Plains in Alfalfa County and found three Plegadis ibises that he believed might be hybrids. He photographed these birds and sent the photos to Joe Grzybowski and David Sibley. Both agreed that these birds were probably hybrids, but Joe also left open the possibility that the third bird (bird D in photos below) was a White-faced in transition between age-class characters. Jim went back to the Salt Plains on June 6th & 7th and found and photographed another probable hybrid.
Hybridization at the Salt Plains may be a local phenomenon where Glossies are rare relative to White-faceds. White-faced Ibises were first found nesting on Ralston Island at the Great Salt Plains in 1995 and have been nesting there every year since. A few temporary nesting colonies of White-faceds also have been located recently in Kingfisher, Tillman and Beaver counties, Oklahoma. Glossy Ibises began showing up in Major and Kingfisher counties during the spring of 2000. This location is less than 30 miles due south of the Great Salt Plains. An adult Glossy in Oklahoma would have few choices other than a White-faced Ibis for a mate. In Texas, around Matagorda and Lavaca Bay Islands where both species nest, hybrids have not been found (or recognized) to date. This may be due to larger numbers of Glossy Ibises there making it easier to find a mate of the same species.
A timely article was published in North American Birds Volume 54 No. 3 2000 entitled "Range Expansion of the Glossy Ibis in North America" by Michael Patten and Greg Lasley. This article discusses the westward expansion that began in the mid to late 1980s. Also discussed in this article is the fact that "the identification of Plegadis ibis requires close views in good light, of bare-part pattern and coloration and feathering around these areas". The authors also wrote about the eastward expansion of the White-faced Ibis but noted that, although hybridization has not yet been detected in the wild, these species do interbreed freely in captivity. The authors state: "Potential hybridization obviously adds a complicated and tricky wrinkle to field identification----" and, as can be seen from the photographs below, these probable hybrids definitely do add to an already difficult identification problem.
We welcome any comments or alternate interpretations on these birds, or information on any other possible hybrids of this group.
James W. Arterburn: firstname.lastname@example.org
Joseph A. Grzybowski: email@example.com
Photos by James W. Arterburn
Photos A1 and A2 (above):
Adult hybrid? – This bird looks like a Glossy at a distance but notice the red in the eye, white in some of the feathers on top of the head just above the loral stripe and on the side of the face near the gape, the blue lines bordering the facial skin arching ever so slightly behind the eye, and the purplish to pinkish cast to the facial skin. Legs show pinkish red primarily at joints.
Photos B1 and B2 (above):
Sub-Adult hybrid? – This bird has characteristics of both species. Notice the brown to brownish-red eye, the facial skin that has both purple and dark gray color, the whitish to purple line bordering the facial skin and encircling the eye, and the white in the feathers on top of the head just above the loral stripe and on the side of the face near the gape.
Photos C1 and C2 (above and below):
Sub-Adult hybrid? – This bird also has characteristics of both species. The eye is red, the facial skin has pink, purple and gray color, and the line bordering the facial skin is white and encircles the eye. Also note white in some of the feathers on top of the head just above the loral stripe and on the side of the face near the gape.
Photos D1 and D2 (above):
Sub-Adult variant White-faced or hybrid? – This bird may just be a variant White-faced Ibis but notice the brown eye, and the purple and gray facial skin. Also notice the red to purple line bordering the facial skin and encircling the eye.
Glossy Ibis photos by Angus Wilson