Vermivora chrysoptera x VERMIVORA cyanoptera
Status: Rare casual spring and fall migrant east.
Documentation: Brewster’s Warbler: photograph, 18 May 2020 Madison Co (Brogie, in gallery); Lawrence’s Warbler: photograph 25 May 2021 Sarpy Co (Swanson, in gallery); F2 or later backcross.
Taxonomy: This species and Blue-winged Warbler V. cyanoptera hybridize frequently and produce fertile hybrids; their genomes are 99.97% identical, with plumage genes accounting for the difference (Toews et al 2016). The genetic basis of this hybridization was described by Confer et al (2020) and appears to be a simple Mendelian system whereby the black transocular line and plain throat of cyanoptera are dominant and the black auricular and throat of chrysoptera are recessive. Thus, Brewster’s Warbler is the F1 hybrid between the two parent species and exhibits the black transocular line and pale throat of cyanea that are inherited together, and Lawrence’s Warbler the (F2 or later) backcross form that exhibits the Mendelian recessive gene combination of the black auricular and throat of chrysoptera. Brewster’s Warbler is more common than Lawrence’s Warbler, as predicted by Mendelian inheritance; Lawrence’s types occur only in the F2 and subsequent generations.
Rather startling was a hybrid between a male Chestnut-sided Warbler and a Brewster’s Warbler found in Pennsylvania 7 May 2018, known as the “Burket Triple Hybrid”; it sang a Chestnut-sided Warbler song, as expected since DNA determined the genetic makeup and found that the male parent was a Chestnut-sided (Grove 2019).
Records: There are six Nebraska records of Brewster’s Warbler, four in spring and two in fall, and one of the recessive form Lawrence’s Warbler. The spring records are rather late in the migration window; hybrids often follow different migration routes and timing than their parent species.
Among the six Brewster’s records, at least two appear to be F2 introgressants, likely F1 hybrids backcrossed with Blue-winged Warblers, in Madison Co 18 May 2020 (Mark Brogie, eBird.org), and Sarpy Co 21 May 2020 (Phil Swanson, eBird.org). See gallery for photographs.
18 May 2020 Madison Co (Mark Brogie, personal communication, photo eBird.org)
19 May 1982 Keya Paha Co (Brogie and Mossman 1983)
21 May 2020 Sarpy Co (Phil Swanson, photo in gallery)
22 May 2022 Sarpy Co (Phil Swanson, personal communication, photographs)
6 Sep 2007 Fontenelle Forest, Sarpy Co
13 Sep 2008 Oak Grove WMA, Seward Co.
The lone Lawrence’s type record is of one photographed by Phil Swanson in his Sarpy Co yard 25 May 2021; it has been suggested it is a backcross between an F1 hybrid and either Blue-winged or Golden-winged Warbler or possibly with an F1 or F2 backcross (Tom Stephenson, personal communication).
Comments: Genetic studies indicate introgression of cyanoptera haplotypes into chrysoptera phenotypes with no reverse movement (Confer et al 2020), indicating that chrysoptera is being replaced by cyanoptera (Confer et al 2020). The only known phenotypically and genetically pure populations of chrysoptera breed in Manitoba, where numbers are increasing (Confer et al 2020), possibly even to the extent of increasing numbers being reported in Nebraska.
Hover mouse over photos below for captions.
Acknowledgements: Photographs (top; Mark Brogie; bottom, Phil Swanson) of apparent F2 backcrosses between Golden-winged Warbler x Blue-winged Warbler and Blue-winged Warbler.
Literature Cited:
Confer, J.L., P. Hartman, and A. Roth. 2020. Golden-winged Warbler (Vermivora chrysoptera), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.gowwar.01.
Grove, D.S. 2019. The Identification of the Burket Triple Hybrid- a Brewster’s/Chestnut-sided Warbler. Pennsylvania Birds 33: 223-225.
Toews, D.P.L., S.A. Taylor, R. Vallender, A. Brelsford, B.G. Butcher, P.W. Messer, and I.J. Lovette. 2016. Plumage Genes and Little Else Distinguish the Genomes of Hybridizing Warblers. Current Biology 26: 2313-2318.
Recommended Citation
Silcock, W.R., and J.G. Jorgensen. 2024. Golden-winged x Blue-winged Warbler (hybrid) (Vermivora chrysoptera x cyanoptera). In Birds of Nebraska — Online. www.BirdsofNebraska.org
Updated 26 Dec 2024