Thick-billed Fox Sparrow (Passerella iliaca megarhyncha group) is the oddly large-billed Sierra Nevadan taxon of the genus Passerella. It is currently classified as a subspecies group within Fox Sparrow.
Thick-billed Fox Sparrows are is almost identical in plumage to Slate-colored Fox Sparrows but have a more extensive blue-gray hood and less rust in the tail.
The most striking feature of this bird is its enormous beak which can appear to be three times as large as that of Slate-colored.
The name “megarhyncha” comes from the Greek mega-, meaning ‘great’, and rhunchos, meaning ‘snout’. A Thick-billed’s beak also differs in color from that of the Slate-colored.
Although the culmens of both groups are grayish brown, Slate-coloreds have yellow lower bills instead of the steel blue of the Thick-billeds’ (Rising 1996).
Breeding / Distribution:
The megarhyncha complex breeds in mountains from southern Oregon to southern California east to the Sierra Nevadas and shows little geographic variation; however, schistacea interbreeds with megarhyncha along a narrow contact zone from southern Oregon to western Nevada.
Call / Song:
Sibley (2000) indicates that this group has the most diagnostic call note, “a high, flat squeak (sic) teep like California Towhee“.
- Rising, J. D. (1996). A Guide to the Identification and Natural History of the Sparrows of the United States and Canada. London: Academic Press.
- Sibley, D. A. (2000). The SibleyGuide to Birds. New York: Chanticleer Press, Inc.
- Zink, R. M. (1994). The Geography of Mitochondrial DNA Variation, Population Structure, hybridization, and Species Limits in the Fox Sparrow (Passerella iliaca). Evolution 48: 96-111.
- Zink, R. M. and Kessen, A. E. (1999). Species Limits in the Fox Sparrow. Birding 31: 508-517.