Following Jeff MacQueen's UVB report of earlier today:

Peculiar growths of bills in birds have recently been a research area  
receiving major attention.

Scroll down to see photos of red-breasted nuthatches at
http://alaska.usgs.gov/science/biology/landbirds/beak_deformity/gallery.html

General account on topic:
http://feederwatch.org/learn/articles/deformed-bills-alaska/

Research studies by a leading investigator of bill deformities:
http://alaska.usgs.gov/staff/staffbio.php?employeeid=152
See publications list, e.g., Handel and Van Hemert 2015, Van Hemert et  
al.
2013, Van Hemert et al. 2012a, Van Hemert et al. 2012b, Van Hemert  
2012c,
Handel et al. 2010, Van Hemert and Handel 2010

In Britain:
http://www.bto.org/volunteer-surveys/gbw/about/background/projects/bgbw/extra
and especially
http://www.bto.org/sites/default/files/u23/downloads/publications/bird-table
/bt65_lr_20-21.pdf

George Clark
Norwich, VT

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