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If you have any other reports of bill deformities (primarily crossed or overgrown bills) in passerines to report, please contact Julie Craves (jac AT rrbo.org); this page will be periodically updated. Please note that due to the high rate of bill deformities on eastern House Finches (which may be connected with the prevalent conjunctivitus disease or genetic bottlenecking) that House Finch reports will not be included.If you post your photos on the online photo sharing site Flickr, there is a photo pool called Birds with Deformed Bills. You can add your photos of any species of bird with a deformed bill by joining the pool.
This compilation of bill deformities is property of the Rouge River Bird Observatory. Do not use or cite without permission.
Maxilla = top; mandible = bottom
Flycatchers to European Starling
Warblers through House Sparrow, and literature cited
Non-North American reports
Bill tumors, most due to avian pox
| Species | Details | Source |
| Tennessee Warbler (Vermivora peregrina) | 25 Sep 1977; HY-U; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Tennessee Warbler | 15 Oct 2005; HY-U; near Amherstberg, Ontario; maxilla twisted and short, overlapping mandible | Holiday Beach Migration Observatory |
| Nashville Warbler (Vermivora ruficapilla) | 6 Nov 1974; HY-F; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Nashville Warbler | 19 May 1997; SY-U; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Yellow Warbler (Dendroica petechia) | Alberta, Canada | (gmbooth AT telusplanet.net) |
| Yellow Warbler | 26 May 1997; SY-F; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr@westol.com) |
| Chestnut-sided Warbler (Dendroica pensylvanica) | 10 Sep 2006; HY-U; both mandible and maxilla tips bent slightly left (like Wrybill); Metro Beach Metropark, Macomb Co., MI | Allen Chartier (amazilia1 AT comcast.net) |
| Cape May Warbler (Dendroica tigrina) | 27 Sep 1974; HY-F; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr@westol.com) |
| Cape May Warbler | 27 Spe 1975; HY-F; Rector, PA; slightly crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr@westol.com) |
| Cape May Warbler | 5 Oct 1984; HY-F; Rector, PA; maxilla crossed right | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Yellow-rumped Warbler (Dendroica coronata) | 27 Oct 1993; HY-M; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnrATwestol.com) |
| Yellow-rumped Warbler | 10 Oct 1994; HY-F; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Blackpoll Warbler (Dendroica striata) | 21 Sep 1986; HY-F; Rector, PA; maxilla crossed left | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Black-and-white Warbler (Mniotilta varia) | 12 Sep 1989; HY-M; Rector, PA; maxilla crossed right, due to injury? | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| American Redstart (Setophaga ruticilla) | 12 Sep 1971; HY-F; Rector, PA; maxilla crossed right | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Worm-eating Warbler (Helmitheros vermivorus) | Sept 2007; Walls of Jericho, Jackson Co., AL; maxilla elongated |
Elliot Schunke (ewschunke AT hotmail.com)
|
| Northern Waterthrush (Seiurus noveboracensis) | 30 April 2007; AHY-U; Dearborn, Wayne Co., MI; maxilla bill eroded and shortened, perhaps healed pox (cross referenced in bill tumor table) | Rouge River Bird Observatory Julie Craves (jcraves AT umd.umich.edu) |
| Hooded Warbler (Wilsonia citrina) | Female; Apopka, FL | Clay Black (clay.black AT swfwmd.state.fl.us) |
| Hooded Warbler | 5 Oct 1969; HY-M; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Hooded Warbler | HY-M; 6 Sep 2003; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Hooded Warbler | HY-M; 10 Sep 2003; Rector, PA; shriveled end of maxilla | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr aT westol.com) |
| Mourning Warbler (Oporornis philadelphia) | 18 Sep 03; HY-F; Burdett, NY; crossed, maxilla shorter than bottom | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo aT att.net |
| Common Yellowthroat (Geothlypis trichas) | 12 Sep 1984; HY-M; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnrAT westol.com) |
| Common Yellowthroat | Northampton Co., VA, fall 1998 | Larry Robinson (LarryRob aT aol.com) |
| Common Yellowthroat | 8 Aug 2003; HY-M; Burdett, NY; entire bill missing back to nares - appears chewed | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| Common Yellowthroat | 1 Sep 2003; HY-M; Burdett, NY; crossed, mandible short | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| Common Yellowthroat | 19 May 2008; AHY-M; near Oahe Dam, Stanley Co., SD; slightly crossed and did not close properly | Doug Backlund (Doug.BacklundAT state.sd.us) |
| Wilson's Warbler (Wilsonia pusilla) | 4 Sep 1977; AHY-U; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnraT westol.com) |
| Yellow-breasted Chat (Icteria virens) | ASY-F; May 1995; CA; maxilla 6.77mm longer than mandible | Thomas Leeman (VentanaWS AT aol.com) |
| Yellow-breasted Chat | 27 May 1972; AHY-M; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Summer Tanager (Piranga rubra) | 10 Sep 2003; HY-F; Rector, PA; slightly crossed at tip | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr aT westol.com) |
| Scarlet Tanager (Piranga olivacea) | 13 Jul 1991; HY-M; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Scarlet Tanager | 20 Jul 1991; HY-F; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Eastern Towhee (Pipilo erythrophthalmus) | 20 Oct 1974; HY-F; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr aT westol.com) |
| Eastern Towhee | 21 Sep 2004; HY-F; Newburyport, MA; severely crossed | Brian Johnson, Joppa Flats Banding Station (baidaj AT yahoo.com) |
| Spotted Towhee (Pipilo maculatus) | AHY-M; 12 May 1999; near Pierre, SD | Doug Backlund (Doug.BacklundAT state.sd.us) |
| American Tree Sparrow (Spizella arborea) | IL; experiment involving high air temperatures caused bill deformities | West 1959 |
| Field Sparrow (Spizella pusilla) | 21 Oct 1961; U-U; Rector, PA; slightly crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Field Sparrow | 31 Oct 1987; U-U; Rector, PA; maxilla crossed right | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Field Sparrow | 15 Jun 1997; AHY-M; Rector, PA; maxilla slightly crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Lark Bunting (Calamospiza melanocorys) | 21 Dec 2007; U-F; Yuma Co., CO; maxilla elongated and downcurved | Bill Schmoker (bill.schmoker AT gmail.com) |
| Song Sparrow (Melospiza melodia) | AHY-F, 23 May 2000, Point au Sauble, Lower Green Bay, WI | Andy Paulios (paulat06 AT uwgb.edu) |
| Song Sparrow | 1 Sep 2002; HY-U; Burdett, NY; severely crossed | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| Lincoln's Sparrow (Melospiza lincolnii) | 8 Oct 1990; HY-U; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Golden-crowned Sparrow (Zonotrichia atricapilla) | AHY-U; 16 Jan 1997; San Francisco, CA; crossed; "overweight" at 41 gr! | Rita Colwell (birding AT ibm.net) |
| White-throated Sparrow (Zonotrichia albicollis) | U-U (not a banded bird); 31 Oct 2001; Tunbridge, VT; severely crossed | Anne Aversa (ataversa AT together.net) |
| White-throated Sparrow | 15 Oct 1971; HY-U; Rector, PA; maxilla long and decurved, slightly crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| White-throated Sparrow also here |
21 Nov 2006; HY-M; maxilla crossed to right; Spring Creek Meadow, High Park, Toronto, Ontario | Toronto Bird Observatory (tboweb ATsympatico.ca) |
| Dark-eyed Junco (Junco hyemalis) | 5 Dec 1976; HY-F; Rector, PA; maxilla badly crossed to right, gap of 2.5 mm | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Dark-eyed Junco | 28 Oct 1987; AHY-M; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Dark-eyed Junco | 9 Nov 1997; AHY-M; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Northern Cardinal (Cardinalis cardinalis) | AHY-F (not a banded bird); 26 Feb 2003; Marietta, GA; mandible severely elongated | Sam Buehner
stamnit AT earthlink.net |
| Northern Cardinal | 3 Sep 2003; HY-M; Dearborn, Wayne Co., MI; flange on left side of mandible (spoon-like) | Rouge River Bird Observatory
Julie Craves (jcraves aT umd.umich.edu) |
| Northern Cardinal | 8 Oct 2003; HY-M; Burdett, NY; excessive keratin on maxilla | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| Northern Cardinal | Jul-Aug 2004; AHY-F; Carol Stream, IL; maxilla spatulate | Dennis Biagoili (DennyRB AT aol.com) |
| Northern Cardinal | 22 May 2006 and 7 Oct 2006; AHY-F; Maxilla 2/3 length of mandible, and crossed over to the right; Metro Beach Metropark, Macomb Co., MI | Allen Chartier (amazilia1 AT comcast.net) |
| Rose-breasted Grosbeak (Pheucticus ludovicianus) | 9 Sep 1904; AHY-F; Illinois?; maxilla sharply downcurved, eye socket misshapen | Woodruff 1907 |
| Rose-breasted Grosbeak | 8 Aug 2002; HY-M; Burdett, NY; deformed on right side, both maxilla and mandible twisted | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| Rose-breasted Grosbeak | 10 Oct 1984; HY-M; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Rose-breasted Grosbeak | 30 Aug 2002; HY-F; Burdett, NY; excessive keratin on maxilla, nearly double normal size | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| Rose-breasted Grosbeak | 27 Aug 2003; AHY-F; Burdett, HY; growth on maxilla - appears to be excessive keratin formation | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| Rose-breasted Grosbeak | 5 Sep 2003; HY-F; Burdett, NY; deformed bill - both excessive keratin on maxilla and misshapen mandible which opened to the sides in an omega shape | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| Yellow Grosbeak (Pheucticus chrysopeplus) | ~27 Jan to 1 May 2006; HY-M; Albuquerque, NM; mandible larger and more massive than maxilla. Image here. May be same bird that appeared in Inyo Co., CA 31 Jul - 2 Aug 2006; image here. Bills looked similar. | |
| Red-winged Blackbird (Agelaius phoeniceus) | July 1992; AHY-M; Ventura Co., CA; mandible split | Jim Greaves (vireos.man AT verizon.net) |
| Red-winged Blackbird | SY-M; 25 May 1976
Livingston Co., MI; maxilla a recurved stump |
Fialia 1981 |
| Red-winged Blackbird | 1 Jun 1968; SY-M; Rector, PA; tips crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Red-winged Blackbird | 19 Mar 2006; two males, SY?; Rowe Sanctuary, Gibbon, NE; elongated with apparently divergent tips | Sharon Stiteler (sharon AT birdchick.com) |
| Red-winged Blackbird | 19 Mar 2006; male, ASY?; Pojoaque, NM; maxilla greatly elongated and wavy, mandible elongated and downcurved | Chuck Hathcock (hathcock AT lanl.gov) |
| Red-winged Blackbird | 26 Feb 2007; ASY-M; Kuna, ID; maxilla greatly elongated (4-5 inches) | Neva Black (nevablack AT hotmail DOT com) |
| Meadowlark sp. (Sturnella magna/neglecta) | Winter 2002; Patagonia, AZ; maxilla and mandible greatly elongaged, especially maxilla | Earle Robinson
(birdfoto2 AT aol.com) |
| Rusty Blackbird (Euphagus carolinus) | 24 Apr 1968; AHY-M; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Common Grackle (Quiscalus quiscula) | 4 Jun 1967; AHY-M; Rector, PA; severely crossed and deformed maxilla | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Common Grackle | June 2008; grossly elongated, keratinized, deformed and downcurved maxilla; Houston, TX | Flickr |
| Brown-headed Cowbird (Molothrus ater) | 20 Jun 2004; SY-M; Ft. Riley, KS, maxilla crossed over bottom | David Rintoul (drintoul AT ksu.edu) |
| Brown-headed Cowbird | 1 May 2000; AHY-M; Brackettville, Kinney Co., TX; crossed | Kevin Ellison (kellis_6 AT yahoo.co.uk) |
| Brown-headed Cowbird | 4 Aug 2004; HY-U; Ft. Hood, Killeen, TX; severely crossed; specimen at Chicago Field Museum Nat. Hist. | Kevin Ellison (kellis_6 AT yahoo.co.uk) |
| Orchard Oriole (Icterus spurius) | 21 Aug 2005; HY-F; upper mandible shortened from tip, and thickened at base; no crossing. Metro Beach Metropark, Macomb Co., MI (photo available from bander). Cross posted at Bill tumor page. |
Allen Chartier (amazilia1 AT comcast.net) |
| Baltimore Oriole (Icterus galbula) | HY-U; July 1996; Rensellaerville, NY, crossed | Anthony Hill (Anthony_Hill AT hotmail.com) |
| White-winged Crossbill (Loxia leucoptera) | AHY-U; 11 Feb 1973; Fairbanks, Alaska; maxilla 15.2mm beyond lower | West 1974 |
| American Goldfinch (Carduelis tristis) | HY-M; 28 Dec 2003; Dearborn, MI, mandible elongated, maxilla crossed | Rouge River Bird Observatory
Julie Craves (jcraves AT umd.umich.edu) |
| 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) |
| Evening Grosbeak (Coccothraustes verspertinus) | Boise, ID; mandible curved to left | Al Larson
(allarson AT micron.net) |
| 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 (see link) |
| House Sparrow | approx fall 2001; maxilla curved down | Flickr |
| House Sparrow | Ohio; 17 Sep 2004; maxilla elongated and scoop shaped | Becky Stanton |
Literature Cited and New ReferencesAnon. 1999. Vermont Institute of Natural Science, Atlantic Flyway review: northeast coastal region 1 -- Fall 1998. N. Amer. Bird Bander 24:54-55.
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. 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. 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.