Setophaga townsendi x virens
Status: Accidental in spring and fall.
Records: There are two:
8 May 2022 Wilderness Park, Lancaster Co (Shari Schwattz, John Carlini; eBird Checklist – 8 May 2022 – Wilderness Park – 40 species (+2 other taxa).
31 Aug 2018 Wildcat Hills Nature Center, Scotts Bluff Co (Mark Brogie; King et al 2021; https://ebird.org/checklist/S48275283).
Comments: The 2018 Nebraska record was pointed out by Jon King; it was originally identified as a Townsend’s Warbler, but hybrid characters can be detected in the eBird photo cited above, including increased black in the face and a yellowish breast.
Regarding the 2022 record, “Steve Mlodinow shared this insight: “The apparent black on crown and streaking on undertail coverts would rule (BTNW [Black-throated Green Warbler]) out. The absence of yellow below the black throat eliminates TOWA [Townsend’s Warbler], but the shape of the black throat and how it comes into the side streaking seems intermediate between BTNW and TOWA.” Mark Brogie and Caleb Strand added: “Classic Townsend’s face but Black-throated Green yellowish vent are major (hybrid) characteristics!””
This hybrid is well known as a result of recent studies by Toews et al (2011) and discussed by Mlodinow et al (2014) with respect to two such hybrids found in Colorado. Toews et al (2011) found “surprisingly extensive” hybridization, some 38% of individuals sampled within the narrow hybrid zone in the Rocky Mountains of northeastern British Columbia. However, most hybrids resembled one or other of the parent species and are thus difficult to detect. It seems quite reasonable to assume that such hybrids would migrate south in fall along the east edge of the Rocky Mountains, where both parent species occur, Black-throated Green albeit rarely (Mlodinow et al 2014; Jon King, pers. comm.). King et al (2021) list 16 records of this hybrid for the US but noted that there are likely many more that pass undetected.
Images
Literature Cited
King, J.C., T. Swope, K. Groeneweg, P. Janzen, and M. Brogie. 2021. Apparent Townsend’s x Black-throated Green Warbler (Setophaha townsendi x virens) hybrids in Kansas and Nebraska. NBR 89: 41-45.
Mlodinow, S.G., G. Walbeck, and D.A. Leatherman. 2014. Two recent records of apparent Black-throated Green Warbler × Townsend’s Warbler in Colorado. Colorado Birds 48: 102-106.
Toews, D.L.P., A. Brelsford, and D.E. Irwin. 2011. Hybridization between Townsend’s Dendroica townsendi and black‐throated green warblers D. virens in an avian suture zone. https://doi.org/10.1111/j.1600-048X.2011.05360.x.
Recommended Citation
Silcock, W.R., and J.G. Jorgensen. 2023. Townsend’s x Black-throated Green Warbler (hybrid) (Setophaga townsendi x virens). In Birds of Nebraska — Online. www.BirdsofNebraska.org
Updated 7 Jul 2023