This compilation of bill deformities is property of the Rouge River Bird Observatory. Do not use or cite without written permission. Copyright for photos is held by photographers. Please do not use without permission from individual listed.
Flycatchers to Horned Lark (pg 1)
Swallows through bluebirds (pg 2)
Thrushes through European Starling (pg 3)
Warblers through towhees (pg 4)
Sparrows through orioles (pg 5)
Purple Finch through House Sparrow + Literature Cited (below)
Bill Tumors, Most Due to Avian Pox
Crossbills through House Sparrow + Literature Cited
|Purple Finch (Haemorhous purpureus)||24 Oct 2016; U-F; Thompson Falls, MT; maxilla slightly elongated||Jim Greaves (lbviman AT blackfoot DOT net)|
|White-winged Crossbill (Loxia leucoptera)||AHY-U; 11 Feb 1973; Fairbanks, Alaska; maxilla 15.2mm beyond lower||West 1974|
|Common Redpoll (Carduelis flammea)||6 Apr 2012; Thompson Falls, MT; maxilla slightly miniaturized||Jim Greaves (lbviman AT blackfoot DOT net)|
|Pine Siskin (Spinus pinus)||19 Oct 12; U-U; Santa Fe, NM; no maxilla; mandible elongated and frayed looking||Maria Higuara (maria AT higuerapope DOT com)|
|American Goldfinch (Carduelis tristis)||HY-M; 28 Dec 2003; Dearborn, MI, mandible elongated, maxilla crossed||Rouge River Bird Observatory, Julie Craves (jac.rrbo AT gmail.com)|
|American Goldfinch||AHY-F; 9 Apr 2007; Walden, Orange Co., NY; very elongated mandible||Mark Eis (markeis AT mac DOT com)|
|American Goldfinch||17 Aug 2007; Lolo, MT; maxilla appears to have been put through a shredder||Jeanne Elliott (jeanne.elliott AT bresnet DOT net)|
|American Goldfinch||20 April 2008; AHY-F; near St. Ignitius, Montana; very slightly shortened maxilla; bird also has patches of white feathers||Eugene Beckes via Judy Hoy (bjhoy AT localnet.com)|
|American Goldfinch||April 2008; AHY/ASY-M; near St. Ignitius, Montana; shortened maxilla||Eugene Beckes via Judy Hoy (bjhoy AT localnet.com)|
|American Goldfinch||20 Oct 2011; U-F; Richland, MI; extremely elongated and downturned maxilla||Reported on MLive news web site|
|Evening Grosbeak (Coccothraustes verspertinus)||Boise, ID; mandible curved to left||Al Larson (allarson AT micron.net)|
|Evening Grosbeak||photo dated 26 Oct 2012; U-M; VT; maxilla thickened and decurved, crossed at tip||Flickr|
|House Sparrow (Passer domesticus)||Cuyahoga, Co., OH; July 2004; male with hugely elongated maxilla, curved down||Maureen McEneryu|
|House Sparrow||23 Sep to at least 14 Oct 2006; Potomac, MD; entire bill greatly enlarged||via Birder's World forum|
|House Sparrow||approx fall 2001; maxilla curved down||Flickr|
|House Sparrow||Ohio; 17 Sep 2004; maxilla elongated and scoop shaped||Becky Stanton|
|House Sparrow||Photo labeled 25 Apr 10; southern NV; tips crossed||Flickr|
|House Sparrow||20 Aug 2010; U-U; Dallas, TX; maxilla nearly absent, mandible grossly enlarged and scoop-shaped||Flickr|
|House Sparrow||21 July 2015; HY-U; Illinois; maxilla spoon-shaped||Flickr|
|House Sparrow||16 Oct 2015; U-F; Kennebunk, ME; slightly crossed at tip||Flickr|
Maxilla = Top, Mandible = Bottom.
Anon. 1999. Vermont Institute of Natural Science, Atlantic Flyway review: northeast coastal region 1 — Fall 1998. N. Amer. Bird Bander 24:54-55.
Craves, J. A. 1994. Passerines with deformed bills. North American Bird Bander 19(1): 14-18.
Fiala, K.L. 1981. Survival of a demaxillate Red-winged Blackbird. Wilson Bulletin 93:563-565.
Green, D. S. 1969. Bill deformity in Clark’s Nutcracker. Blue Jay 27:36.
Eltzroth. E. 1996. Cross-beaked Western Bluebirds. Sialia 18:3-4.
Ferreira de Vasconcelos, M. and M. Rodrigues. 2006. Bill deformity in a White-winged Becard (Aves: Subsocines: Tityridae) from Minas Gerais, Brazil. Revista Brasileira de Ornitologia 14:165-166.
Kinch, B. 1998. Deformed chickadee. Ontario Birds 16:45-46.
Small, M. F., & C. L. Pruett. 1998. Rhamphothecal hyperkeratosis in a Bronzed Cowbird. Bull. Texas Ornithol. Soc. 31: 27–29.
Sogge, M. K. and E. H. Paxton. 2000. A summary of observed physical deformities in the Willow Flycatcher: 1996-2000. U.S.G.S. Forest and Rangeland Ecosystem Science Center, Colorado Plateau Field Station, Flagstaff, AZ.
Sperry, D, D. Cimprich, and J. Marquess. 2007. Beak deformity in the endangered Black-capped Vireo. N. Amer. Bird Bander 32: 1-3.
Speirs, J.M. and M. Wilson. 1994. Blue Jay with “crossed” bill. N. Amer. Bird Bander 19:100.
Van Hemert, C. R. 2007. Alaskan Birds at Risk: Widespread Beak Deformities in Resident Species (pdf). Birding 39 (5):48-55.
West, G.C. 1959. Effects of high air temperature on the bill and claw keratin structures of the tree sparrow. Auk 76:534-537.
—–. 1974. Abnormal bill of a White-winged Crossbill. Auk 91:624-626.
Woodruff, F. M. 1907. Malformed bill of Rose-breasted Grosbeak. Auk 24:220-221.