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Deformed bills in songbirds (passerines) are uncommon, perhaps because they are further down the food chain and have less opportunity to accumulate toxins, perhaps because bill deformities pose a more serious threat to survival for small birds, or for a host of other reasons. There are many factors that may contribute to deformed bills in birds.After banding a Gray Catbird with a grossly crossed bill in 1993, the Rouge River Bird Observatory's Julie Craves looked into the incidences of passerines with deformed bills. Her article, Passerines with deformed bills, was published in the journal North American Bird Bander. It provides a primer on the anatomy of bird bills, discusses possible causes for bill deformities, and several tables summarize reports of passerines with deformed bills from the literature. As you'll see in her paper, Icterids (the blackbird family) and Mimids (catbirds, mockingbirds, and thrashers) appear to have a higher rate of bill deformities than other families.
Since the publication of the article, other reports of birds with deformed bills have surfaced. The Tables below list reports that the author has become aware of.
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.This compilation of bill deformities is property of the Rouge River Bird Observatory. Do not use or cite without permission.
I've had to split up the page:
Flycatchers to European Starling (below)
Warblers through House Sparrow, and literature cited
Bill tumors, most due to avian pox
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Source |
| Western Wood-Pewee (Contopus sordidulus) | Fall 2003; Great Falls, MT; severely crossed | Judy Hoy (bwrehab AT mtwi.net) |
| Willow Flycatcher (Empidonax traillii) | 1996-2000; 13 birds with bill deformities in various western states | Sogge and Paxton (2000) |
| "Traill's" Flycatcher (Empidonaxtraillii/alnorium) | 21 Aug 1975; HY-U; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| (Least) Bell's Vireo (Vireo belli) | May 1980; AHY; Santa Barbara, CA | Jim Greaves (vireos.man AT erizon.net) |
| Red-eyed Vireo (Vireo olivaceus) | Ft. Morgan, AL | Bob Sargent (RubyThroat AT aol.com) |
| Red-eyed Vireo | 11 Sep 1987; HY-U; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Red-eyed Vireo | 30 Jul 2004; HY-U; Oxford, OH; upper bill crossed | David Russell (russeld AT muohio.edu) |
| Black-capped Vireo (Vireo atricapilla) | 8 May 2006; AHY-M; Fort Hood, TX; lower bill right, upper bill tip downward (condition not as pronounced when first captured on 5 Jun 2005) | Sperry et al. 2007 |
| Least Bell's Vireo (Vireo bellii) | CA | Jim Greaves (vireos.man AT verizon.net) |
| Steller's Jay (Cyanocitta stelleri) | 25 Jan to 10 Jun 2005; Berkely, CA; both mandibles strongly decurved downward | Terry Coddington (tlcodd AT earthlink.net) |
| Blue Jay (Cyanositta cristata) | Alberta, Canada | (gmbooth AT telusplanet.net) |
| Blue Jay | Pickering, Ontario, Canada; crossed bill | Spiers and Wilson 1994 |
| Blue Jay | 1 May 1973; SY-U; Rector, PA; crossed mandibles | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Blue Jay | 28 April 2007; AHY (ASY?)-U; near Bethlehem, PA; both mandibles decurved downward | Jim Figlar (figlar AT pdt DOT net) |
| Florida Scrub-Jay (Aphelocoma coerulescens) | 15 May 2003; Lake Wales Ridge State Forest, Polk Co., FL; top crossed left | Bill Pranty (billpranty AT hotmail.com) |
| Western Scrub-Jay (Aphelocoma californica) | 27 Apr 2004; Oakland, CA; hooked upper bill | Debbie Viess (amanitarita AT mindspring.com) |
| Clark's Nutcracker (Nucifraga columbiana) | 24 Feb 2007; Island Park, ID; top sideways, hugely overgrown, and curled upwards | Cliff Weisse (ClifffAndLisa AT octobersetters.com) |
| Clark's Nutcracker | Jasper Nat'l Park, Saskatchewan, Canada, crossed | Green 1969 |
| Corvus sp. (C. brachyrhynchos or C. caurinus) | 14 Jan 2008; Coupeville, Island Co., WA; upper bill slightly enlongated and hooked down | Craig Johnson highseasmarine AT comcast.net |
| Corvus sp. (C. brachyrhynchos or C. caurinus) | 5 Mar 2003; upper bill very elongated and curved down; Mukilteo, WA | Judy Rowe Taylor
(judyrowetaylor AT comcast.net) |
| American Crow (Corvus brachyrhynchos) | Chillicothe, OH; badly crossed | Joe McMahon (jmcmahon AT zoonet.net) |
| American Crow | 17 Apr 2004; Bellvue and Mukilteo, WA (presumably same bird) | Megan Lyden (meganlyden AT msn.com) |
| Common Raven (Corvus corax) | 5 Nov 2006; Samish Flats, Skagit Co., WA; upper mandible curved and slightly hooked down at end, longer than lower mandible, gap between mandibles when bill was closed | Dennis Paulson (dennispaulson AT comcast DOT net) |
| Common Raven | 26 Sep 2006; Dunraven Pass; Yellowstone National Park (WY); upper mandible overgrown | Ralph Kerr (ralphk48 at Adelphia.net) |
| Common Raven | 18 Mar 2008; |
John (bewickwren AT earthlink DOT net) |
| Brown Creeper (Certhia americana) | 27 Oct 1996; HY-U; Rector, PA; mandibles crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Carolina Chickadee (Poecile carolinensis) | late Oct 2005; U-U; Crosby, Harris Co., TX; upper mandible twice as long as lower, curved down | Ricci Deibert (riccideibert AT hotmail.com) |
| Chestnut-backed Chickadee (Poecile rufescens) | Alaska | (libor@atlas.geomatics.com) |
| Black-capped Chickadee (Poecile atricapillus) | southcentral Alaska; 500+ birds, mostly with very elongated upper mandibles since 1991, most in the last couple years | Colleen Handel (colleen_handel
AT usgs.gov)
USGS Alaska Biological Science Center (click here for more info) Van Hemert 2007 |
| Black-capped Chickadee | Kenabeek, Ontario | Kinch 1998 |
| Black-capped Chickadee | 11 Oct 2005; HY-U; upper mandible was elongated and crossed over the bottom; Rector, PA | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Black-capped Chickadee (?) | 26 Nov 2006; HY-U; upper mandible 9mm long and twisted left, lower 7mm and twisted right, bird also small, possibly Carolina Chickadee (P. carolinensis) or hybrid; Schuylkill Haven, PA | Scott Weidensaul (scottweidensaul AT verizon DOT net) |
| Black-capped Chickadee | 2007; U-U; upper mandible slightly elongated; Whidbey Island, Island Co., WA | Craig Johnson (highseasmarine AT comcast.net) |
| Blue Tit (Parus caeruleus) | Great Britain | Andy Mitchell (andy AT witsend.freeserve.co.uk) |
| Tufted Titmouse (Baeolophus bicolor) | 1 Feb 1999; SY-U; Rector, PA; upper mandible crossed right | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Red-breasted Nuthatch (Sitta canadensis) | 28 Mar 2004; AHY-M; Dearborn, MI; lower mandible elongated and crossed to right | Rouge River Bird Observatory
Julie Craves (jcraves AT umd.umich.edu) |
| White-breasted Nuthatch (Sitta carolinensis) | Winter 2001-02; Gardener, MA | Sigrid Warren
(kolibri23 AT msn.com) |
| White-breasted Nuthatch | 8 Mar 2004; AHY-F; Grosse Pointe, MI; lower mandible greatly elongated and crossing up and to left, upper moderately elongated and crossing down and to right |
Bill Rapai via Julie Craves, Rouge River Bird Observatory jac AT rrbo.org |
| White-breasted Nuthatch | 25 Apr 2003; Jackson, NH; 'very crossed' | Scott Woodman (scotttheguy AT msn.com) |
| Winter Wren (Troglodytes troglodytes) | 29 Sep 2006; HY-U; Tip of mandible broken off, maxilla appeared extra long and downcurved; Metro Beach Metropark, Macomb Co., MI | Allen Chartier (amazilia1 AT comcast.net) |
| American Dipper (Cinclus mexicanus) | Spring 2004; bird banded as normal juvenile 18 Jul 2003 in Whitewood Creek, SD returned dead with bill slightly crossed at tip | Doug Backlund (Doug.Backlund AT state.sd.us) |
| Golden-crowned Kinglet (Regulus satrapa) | HY-F; 20 Oct 02; Holiday Beach, Essex Co., Ontario, Canada | Allen Chartier (amazilia1 AT comcast.net |
| European Blackbird (Turdus merula) | Great Britain | Andy Mitchell (andy AT witsend.freeserve.co.uk) |
| Nightingale (Luscinia megarhynchos) | Great Britain | Andy Mitchell (andy AT witsend.freeserve.co.uk) |
| Western Bluebird (Sialia mexicana) | U.S. | Eltzroth 1996 |
| Mountain Bluebird (Sialia currucoides) | late March 2008; Sanders Co MT; top mandible slightly elongaged and hooked | Jim Greaves (vireos.man AT verizon.net) |
| Veery (Catharus fuscescens) | HY-U; 14 Sep 2004; Burdette, NY; upper mandible crossed to left, gap 5mm [looks like an injury] | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| Gray-cheeked Thrush (Catharus minimus) | "...grossly deformed bill." Woodstock, VT | Anon. 1999 |
| Swainson's Thrush (Catharus ustalatus) | HY-U; 29 Sep 94; Dearborn, Wayne Co. MI; severely crossed, lower also curved down and gave jaw a dislocated look | Rouge River Bird Observatory
Julie Craves (jcraves AT umd.umich.edu) |
| Swainson's Thrush | 21 Sep 1977; AHY-U; Rector, PA; lower bill crossed to left | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Gray Catbird (Dumetella carolinensis) | 3 in Ft. Morgan, AL | Bob Sargent (RubyThroat AT aol.com) |
| Gray Catbird | AHY-F; 2 Jun 95, Dearborn, Wayne Co. MI; slightly crossed at tip | Rouge River Bird Observatory
Julie Craves (jcraves AT umd.umich.edu) |
| Gray Catbird | HY-U; 11 Sep 01, Dearborn, Wayne Co. MI; slightly crossed at tip | Rouge River Bird Observatory
Julie Craves (jcraves AT umd.umich.edu) |
| Gray Catbird | 28 Sep 1963; U-U; Rector, PA; slightly crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Gray Catbird | 2 Sep 1995; AHY-U; Rector, PA; crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT estol.com) |
| Gray Catbird | HY-U; 4 Sep 03; Rector, PA; severely crossed bill | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Gray Catbird | AHY-U; 17 May 2001; near Pierre, SD | Doug Backlund (Doug.Backlund AT state.sd.us) |
| Gray Catbird | AHY-U; 14 Oct 2004; Tiffin , OH; extremely elongated upper mandible showing erosion similar to pox | Deb Plotts, Miller Stonebraker
Bird Observatory
(dplotts AT woh.rr.com) |
| Gray Catbird | HY-U; 7 Sep 05, Dearborn, Wayne Co. MI; top slightly crossed at tip, 2 mm to right | Rouge River Bird Observatory
Julie Craves (jcraves AT umd.umich.edu) |
| Gray Catbird | HY-U; 19 Sep 05; Oahe Dam, Stanley Co., SD; severely crossed (see photo) | Doug Backlund (Doug.Backlund AT state.sd.us) |
| Gray Catbird | HY-U; 15 Aug 06, Dearborn, Wayne Co. MI; bill slightly short and curved to right, top more so than bottom; slight gap when closed | Rouge River Bird Observatory
Julie Craves (jcraves AT umd.umich.edu) |
| Gray Catbird | U-U; 26 Sep 2006; near Pierre, SD | Doug Backlund (Doug.Backlund AT state.sd.us) |
| Northern Mockingbird (Mimus polyglottos) | Adult, with young; 4 Sep 05; Santa Barbara, near Laguna Creek adjacent to sewage treatment plant, CA (see photo) | Jim Greaves (vireos.man AT verizon.net) |
| Northern Mockingbird | HY-U; 2 Oct 2007; Santa Clara, CA, upper mandible | Jim Chuq Von Rospach (chuqvr AT gmail.com) |
| Brown Thrasher (Toxostoma rufum) | Ft. Morgan, AL | Bob Sargent (RubyThroat AT aol.com) |
| Brown Thrasher | 1 Nov 1983; HY-U; Rector, PA; lower mandible crossed left | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Brown Thrasher | 28 Apr 2004; DeBary, FL; elongated and crossed | Peter May (peter.may AT stetson.edu) |
| Brown Thrasher | May 2007; AHY-U; Birmingham, AL; elongated and downcurved | Tom O'Neil, via Flickr |
| Bendire's Thrasher (Toxostoma bendirei) | 19 Apr 2006; Portal, Cochise, Co., AZ; lower bill elongated | Doug Backlund (Doug.Backlund AT state.sd.us) |
| American Robin (Turdus migratorius) | 31 Jul 2003; HY-U; Burdett, NY; bill and lower skull severely deformed | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| American Robin | 6 JOct 2003; HY-U; Burdett, NY; upper mandible slightly crossed right | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| American Robin | June to at least 8 Nov 2007; AHY-U (M?); Shoreline, King Co., WA; upper mandible short and curled upward | Christine Southwick (clsouth AT u.washington.edu) |
| Cedar Waxwing (Bombycilla cedrorum) | 9 Aug 1997; HY-U; Rector, PA; badly crossed mandibles | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Cedar Waxwing | 5 Jun 1991; AHY-F; Rector, PA; bill crossed | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Cedar Waxwing | 25 May 1996; SY-M; Rector, PA; upper mandible crossed left | Powdermill Nature Reserve
Robert S. Mulvihill (mulvipnr AT westol.com) |
| Cedar Waxwing | 6 Aug 2003; HY-U; Burdett, NY; upper mandible, missing from nares- appears genetic and not injury | John & Sue Gregoire
Kestrel Haven Avian Migration Obs. khmo AT att.net |
| European Starling (Sturnus vulgaris) | 2001; U-U; Nashville, TN; severely overgrown upper mandible (several inches), slightly downcurved |
Barbara
Harris |
| European Starling | Nov 2007; U-U; St. Louis, MO; severely overgrown upper mandible (several inches), slightly downcurved | Dana Perantie danap AT npg.wustl.edu |
| European Starling | 7 Oct 1992; HY-F; Dearborn, Wayne Co., MI; malformed upper bill | Rouge River Bird Observatory
Julie Craves (jcraves AT umd.umich.edu) |
| European Starling | 22 Dec 2007; Buena Vista CBC, Kern Co., CA; upper mandible greatly elongated and downcurved | Alison Sheehey (natureali AT lightspeed.net) |
Part 2: Warblers through House Sparrow, and literature cited