Black-Capped Chickadee Beak Deformity

First seen in the winter of 1991-92, Black-Capped Chickadee beak deformities are now quite common, according to the Alaska Science Center.  To date, there have been over 2100 reports of chickadee beak deformities in Alaska, and only 31 outside of Alaska.  In the photo above, you can see that the chickadee’s beak is at least twice as long as it should be, and the bottom part is crossed and curved up.

The Northwestern Crow suffers from this malady as well, with an astounding 17% of adult birds in Alaska exhibiting some level of beak deformity (as opposed to 6-10% of adult Black-Capped Chickadees).

Other birds with reported beak deformities are the Black-Billed Magpie, Red-Breasted Nuthatch, and Stellar’s Jay – although none of these reports come anywhere close to the high number of sightings of the Black-Capped Chickadee.  Other species of chickadee have been seen with the problem too but they number under 10 total.  Whatever the source of the problem, Black-Caps are especially vulnerable to it.

This map (from shows locations of Black-Capped Chickadee beak deformity sightings.  At first they were centered around Bristol Bay and the Mat-Su Valley but they soon spread to Fairbanks (where I live) and elsewhere.  There are plenty of sightings in remote locations so the problem does not exist only in populated areas.

The poor creatures with deformed beaks often have a very hard time eating – it’s actually kind of amazing that they do get by at all.  The one on the right kept rubbing the elongated portion of its beak on the wood of our feeder, as if attempting to rub it off.  No doubt feeders and even garbage help to keep them alive but mortality is undoubtedly higher among them.  Normal preening is greatly disrupted.  And though many of them do find a mate and breed, fewer eggs hatch to a pair in which the female is deformed and fewer young survive when the male is deformed.

Possible causes are contaminants, nutritional deficiencies, disease, genetic abnormalities and parasites.  Read more about those at

On the left is an example of a normal beak.


6 responses

  1. The poor things 😦 My Audubon Encyclopedia of Birds also suggests that malformations may occur after injuries. Apparently when the upper and lower beaks are out of line and no longer wear on each other, either is more likely to start growing unchecked. Could there be some food that chickadees mostly eat that’s causing them to injure their beaks? I know that even in winter, most of their diet consists of insects, but they’re quite keen on those black oil sunflower seeds too if they can find them at feeders. I don’t know about magpies, but red-breasted nuthatches and jays love those particular seeds too. Mold at feeders might be another problem.

    June 11, 2012 at 1:39 pm

    • I would wonder about it having something to do with feeders, or the food itself, but beak deformities occur in areas with no feeders, and sometimes the affected birds have other deformities along with the beaks. Also, crows aren’t really feeder birds and they are greatly affected. Mold at feeders is a problem though, I do believe that. I’ve been thinking of switching to metal so it’s easier to clean.

      Thanks for your comments 🙂 It’s a fascinating, if sad, subject, and all scientists really have been able to figure out is that there are multiple things that can cause beak deformities. Let’s hope there is a breakthrough soon and that whatever it is, it’s something we can fix.

      June 13, 2012 at 4:50 am

    • New York Times article with links to more information on “avian keratin disorder”:

      June 23, 2012 at 6:21 am

  2. Probably not a bad thing that the survival rate is lower among the deformed bird’s chicks because the more they breed the more deformed birds you get.

    July 28, 2012 at 6:18 am

    • I suppose that would be true if it’s genetic, or if it’s a sickness or fungus or something that could be passed along to the chicks.

      July 28, 2012 at 7:06 am

  3. lee

    Saw a chickadee with an extra-long beak at one of my pine cone suet feeders yesterday afternoon. Thanks for the info about it on this blog.

    March 13, 2015 at 6:23 pm

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