An instance of hybridization with Common Grackle (Quiscalus quiscula) and male parental care by Great-tailed Grackle (Q. mexicanus)

Abstract

Great-tailed Grackle (Quiscalus mexicanus) and Common Grackle (Q. quiscula) are phylogenetically distant among grackles and were historically allopatric. Northward range expansion of Great-tailed Grackle and westward expansion of Common Grackle brought these species into increasing contact over the past century but has not led to notable interactions. Hybrids of Great-tailed Grackle with Boat-tailed Grackle (Q. major), Brewer's Blackbird (Euphagus cyanocephalus), and Red-winged Blackbird (Agelaius phoeniceus) have been reported, whereas hybridization of Common Grackle has never been documented with any species. We report a brood of 2 hybrid offspring of a male Great-tailed Grackle and female Common Grackle in Dillon, Montana, in 2015. For about a week after their discovery, both parents defended and fed the fledglings, the latter behavior extraordinary for a male Great-tailed Grackle. Moreover, whereas the female parent was no longer seen, the male continued to feed the young for at least another 7 weeks after they left the nest tree, during which time the trio moved ∼2 km across town and the young began prebasic molt, growing iridescent blue-black secondary coverts as expected for male Great-tailed Grackle but not for Common Grackle or female Great-tailed Grackle. Analysis of DNA from a feather of one offspring confirmed that it had hybrid nuclear DNA, had Common Grackle mitochondrial DNA, and was male. In 2016, the male Great-tailed Grackle again courted a female Common Grackle that nested in his tree, a nest which he defended, but she was also attended by a male Common Grackle. She produced 5 young, all of which were genetically pure Common Grackles, not hybrids. Also notable in 2016, another male Great-tailed Grackle in the general vicinity was observed feeding young in 1 of 3 nests that he defended, suggesting that male parental care may be more common in that species than has been appreciated.