Chickadees with Deformed Bills

WC has had emails from several readers reporting Black-capped Chickadees at their feeders with seriously deformed bills. As an example, this photo was taken by WC last week at WC’s feeders:

Black-capped Chickadee with Deformed Bill

The leading researcher on this issue is Colleen Handel, who works out of Anchorage. WC has relied upon her research for this post, and interested readers looking for more information can visit the Alaska Science Center site for more information.

The condition has been observed in some 30 species, but it is most common in Black-capped Chickadees and Northwestern Crows, followed by less common Red-breasted Nuthatches, Black-billed Magpies and Steller’s Jays.

Species	# Individuals
Black-capped Chickadee	2,160
Northwestern Crow	148
Red-breasted Nuthatch	75
Black-billed Magpie	6
Steller’s Jay	39

But as the data show, it is overwhelmingly a problem for Black-caps. Why the condition doesn’t affect Boreal Chickadees and, in Southcentral, Chestnut-backed Chickadees, who inhabit the same areas and share the same feeders, is just one of the mysteries.

The locations of birds with the bill deformities have been mapped:

Reports of Black-capped Chickadees with Bill Deformities

You’ll note at once that the maps tracks primarily the areas with feeders: southcentral Alaska and the interior. But the reports from western Alaska suggest it may be more than folks with feeders noticing a pre-existing problem.

In Black-capped Chickadees, the bill deformities probably result in higher mortality rates, both from inability to forage effectively and from heat loss from the inability groom and preen. When birds with bill deformities nest, their children have higher mortality rates as well.

Research has failed to turn up a clear cause. Right now, the focus is on calcium uptake problems, but the cause of those problems isn’t clearly undestood.

You can help Colleen Handel with her study by reporting birds with bill deformities to her project. There’s a report page with instructions here.