Sialia sialis x currucoides
Status: Accidental in summer
Record: Two broods were produced by a pair comprised of a male hybrid Eastern X Mountain Bluebird and a female Mountain Bluebird in Dawes Co in 1985 (Wilson 1985, 1986).
Comments: Hybridization between Eastern and Mountain Bluebird has been found to occur on occasion; in the Nebraska case cited above, the young in both broods showed some warm brown in their underparts (Wilson 1986). Hybrids are fertile and readily mate with both parental species (Rounds and Munro 1982). Hybridization between these species occurred in less than one percent of over 8000 pairs of the two species in southwestern Manitoba (Rounds and Munro 1982). eBird.org (accessed Feb 2021) shows only four records of this hybrid, three from Canada and one from Wisconsin; in all four cases, one of the pair was far out of range. Wilson et al (1986) suggested that hybridization in the Nebraska case may have resulted from low numbers of summering Eastern Bluebirds in the area and the resulting shortage of mates. A male Mountain Bluebird, far east of its normal range, mated with a female Eastern Bluebird in Riley Co, Kansas, in 1997 and fledged several young (Cavitt et al 1998).
Cavitt, J.F., A.T. Pearse, and D.A. Rintoul. 1998. Hybridization of Mountain Bluebird and Eastern Bluebird In Northeastern Kansas. Kansas Ornithological Society Bulletin 49: 21-25.
Rounds, R.C., and H.L. Munro. 1982. A review of hybridization between Sialia sialis and S. currucoides. Wilson Bulletin 94: 219-223.
Williams, F. 1985. Southern Great Plains Region. American Birds 39: 931-933.
Wilson, B.L., J. Minyard, H. Minyard, and T.E. Bray. 1985. Hybrid bluebirds in the Pine Ridge. NBR 53: 67.
Wilson, B.L., J. Minyard, and H. Minyard. 1986. Hybrid bluebird update. NBR 54: 26-27.
Silcock, W.R., and J.G. Jorgensen. 2021. Eastern x Mountain Bluebird (hybrid) (Sialia sialis x currucoides). In Birds of Nebraska — Online. www.BirdsofNebraska.org
Updated 24 February 2021