Plegadis falcinellus x chihi
Status: Rare casual spring and summer visitor statewide.
Records: At least 35 presumed hybrids have been reported in Nebraska through spring 2021 since the first was photographed in Fillmore Co 21-22 May 2004 (Silcock 2004). Almost all records are in Apr and May, with early dates 13, 16, and 16 Apr. Records after May are 15 Jun 2018 Garden Co, 5 Jul 2020 Morrill Co, and 2 Sep 2019 Garden Co. A surprising 11 hybrids were reported in spring 2020 along with 22 Glossy Ibis.
Comments: Presumed hybrids with White-faced Ibis (P. chihi) occur with some regularity on the Great Plains, complicating identification (Arterburn and Grzybowski 2003). Oswald et al (2019) found weak reproductive isolation between the two species and no selection against hybrids; many individuals that had mixed ancestry were later generation hybrids, suggesting that hybrids were not selected against and were fully capable of breeding and producing offspring.
The number of hybrid ibises reported in Nebraska and elsewhere has lagged behind the increase in reports of Glossy Ibis, suggesting hybridization may only occur infrequently (Jorgensen and Silcock 2015) although Oswald et al (2019) found little evidence for assortative mating. It is likely that hybrids and introgressants may be under-reported as observers tend to study these birds less critically as time passes.
Photograph (top) of a Glossy x White-faced Ibis (hybrid) at Oak Lake Park, Lancaster Co 18 Apr 2020 by Michael Willison. Note pinkish-purplish facial skin.
Arterburn, J.W., and J.A. Grzybowski. 2003. Hybridization between Glossy and White-faced Ibises. North American Birds 57: 136-139.
Jorgensen, J.G., and W.R. Silcock. 2015. First Nesting Record and Status Review of the Glossy Ibis in Nebraska. NBR 83: 139-149.
Oswald, J.A., M.G. Harvey, R.C. Remsen, D.U. Foxworth, D.L. Dittmann, S.W. Cardiff, and R.T Brumfield. 2019. Evolutionary dynamics of hybridization and introgression following the recent colonization of Glossy Ibis (Aves: Plegadis falcinellus) into the New World. Molecular Ecology 2019: 1-17.
Silcock, W.R. 2004. Spring Field Report, March-May 2004. NBR 72: 38-58.
Silcock, W.R., and J.G. Jorgensen. 2021. Glossy x White-faced Ibis (hybrid) (Plegadis falcinellus x chihi). In Birds of Nebraska — Online. www.BirdsofNebraska.org
Updated 2 Jun 2021