Newly discovered hybrid zone between Colima and Virginia’s Warbler in Texas

Another case of hybridization in Wood-warblers.

If you want to study avian hybridization, the Parulidae family (Wood-warblers) is an obvious choice. Since 1980, hybrids have been documented in 24 out of 45 species (based on a 2014 paper). A recent study in Texas adds another hybrid to the list: Colima Warbler (Oreothlypis crissalis) x Virginia’s Warbler (O. virginiae).

A Virginia’s Warbler (from: http://www.audubon.org/)

 

Surveys in the Davis Mountains

In June 1999, extensive surveys in the Davis Mountains revealed the presence of singing Colima Warblers, the first documented occurrence outside of its main breeding distribution in the Chisos Mountains. More efforts were put into locating additional territories of this species. During this search it became apparent that some Colima Warblers showed plumage characteristics and song patterns that were similar to Virginia’s Warbler. Could these be hybrids?

A Colima Warbler (from: http://www.audubon.org/)

 

Intermediate Plumage and Song Patterns

Several birds were caught on camera or trapped with mist nests. Morphological analyses confirmed previous observations: they exhibited plumage patterns that were intermediate between both parental species. Overall, the body plumage is darker than the gray of a typical Virginia’s Warbler, but the yellow tail coverts and the lighter gray head and underparts lead to a more Virginia-like appearance. There is, however, considerable variation in plumage patterns, suggesting some degree of backcrossing.

The morphological evidence was corroborated with acoustic data. Between 1999 and 2006, the songs of several birds were recorded. Interestingly, putative hybrids responded more strongly to ‘hybrid songs’ compared to recordings of pure species.

The morphological and acoustic data already point to hybrids in the Davis Mountains, but genetic analyses will be necessary to characterize this newly discovered hybrid zone in more detail.

A hybrid Virginia’s x Colima Warbler (picture courtesy of Kelly B. Bryan)

References

Bryan, K.B. & Lockwood, M.W. (2018) Plumage Characteristics and Song Patterns of Presumed Colima x Virginia’s Warbler Hybrids in the Davis Mountains of Texas. North American Birds, 70(2): 142-154.

 

This paper has been added to the Parulidae page.

Thanks to Darren Irwin for pointing this study out to me and to Kelly Bryan for sending me the PDF and pictures!