Sunday, November 8, 2009

An amazing white-breasted robin finishes the season

This stunning and unusual American Robin with a white breast was the highlight of our final day of banding for the fall 2009 season today. Our short, final week was not particularly notable; I'll be posting a season summary in a few days. Meanwhile, let's check out this very cool robin!

American Robins with abnormal plumage are not terribly uncommon. There was the funky orange-faced bird I banded a couple of weeks ago. I band robins with one or a few white feathers at least once a season. In October 2007 I banded an adult female in which nearly all the gray feathers had a frosted appearance (scroll down on this page for a photo). I have found photos of quite a few robins that were the "opposite" of our bird, with pale backs but normal breasts (in Minnesota, Saskatchewan, Iowa, Pennsylvania, and Utah). However, I have never encountered or heard of a robin that had a completely white breast with a normal back, wings, and head like the bird we banded today.

Most of the gray plumage on this robin, which was a hatching-year bird (born this year), was normally-colored. It did have a few partially white feathers on each wing. Most of these feathers were short and/or deformed. On the left wing there was one slightly brittle short feather with a bit of white, and one mostly white feather next to it.

On the right wing, one primary was half white, stunted, and growing in this weird direction. About half of the tail feathers were also "messy" looking, due to some brittleness and twisting to them.

The only hint of orange pigment was on a few feathers under each wing.

This condition is usually called "leucism," which is an abnormal reduction in the deposition of pigment in the feathers. Some leucistic birds appear entirely washed out or pale if the reduction of pigment is roughly equal in all feathers (some authors now call this "hypomelanism"). More often, pigment is absent in only some feathers, and this is known as pied leucism, or "partial amelanism." Both the grayish-brown and orange/rust feathers on robins are colored by various types of melanin pigments.

There are a number of causes for this type of plumage abnormality. Some are environmental, including injury, disease, or malnutrition. Others are genetic. In the dozens of pied leucistic birds that I have handled, I have never noted the white or pale feathers being deformed in any way. This tends to make me believe that this robin's problems were genetic in some way. The bird appeared healthy otherwise.

This was the last robin -- the 391st -- of the season, and a pretty cool way to wrap up fall 2009.

12 comments:

Angie S said...

Very interesting.
I've never heard of a white-breasted robin before.

Sally Scheer said...

How cool is that??!! He's really beautiful too. Is it likely that the next crop of feathers will come in normally colored and shaped? Have other leucistic birds been recaptured and found to be normally colored in future years?

Julie Craves said...

Whether or not a non-pigmented feather will come in pigmented or not when it re-grows really depends on the underlying cause. The "frosty" robin from 2007 I mentioned had normal feathers that were growing in with a loss of pigment. That was probably due to something external, so that bird might be more likely to re-grow normal feathers next time around.

I think this bird probably had some other, physiological issue, and wouldn't be surprised if it always has a "pigment problem." The deformed feathers could be a liability. They were more fragile (so they'll break off) and the odd way some were growing could also reduce flight precision, especially if new feathers have an even higher incidence of deformity.

Julie Craves said...

I wrote that before my first cup of coffee. Pardon all the awkward phrasing!

OpposableChums said...

VERY cool bird!

As you point out, Robins are no strangers to leucism, but I've only seen it as the pied leucism you describe, not as a wash, as on this startling specimen!

Thanks for the pix.

Cristi in VA said...

Thank you so much for your blog. I just spotted an identical robin in my backyard and your photos and info on leucism helped me identify the bird and reason for his coloration! Very informative. I'll be sure to look at his leg for a band if I see him again!

Anonymous said...

I had never witnessed this before this year when I saw a Robin with white breast feathers. Curiosity led me to google this and find your blog. Very glad to learn about this phenomenon. Thanks! Tom, Indiana

Anonymous said...

I have had a white breasted robin hanging around my house for the past couple of weeks. It's belly is as white as snow. Amazing!

Fred Thompson said...

Interesting story and photos, the white breast on this robin is amazing. I have photographed a few leucistic birds and animals, the on you have the link to in Pa. is one of my photos. I have also photographed a leucistic Tufted Titmlouse, Whitetail Deer, Albino Squirrel, they all are neat to see.

Fred Thompson
wildlifebyfred.com

inchirieri apartamente cluj said...

Really nice pictures, and a great article. I never knew about this. I haven't seen a leustic bird before, or at least I haven't realised than that is something wrong with its plumage.

news games said...

wooow it is just stunning and I LOVE IT !! Amazing pictures...

SheilaSB said...

This morning (Friday, June 10, 2011), I saw a white-breasted robin in the street in front of my house in Argos, Indiana. The bird flew to the shade trees in my yard, so I will hope to see it again as robins usually are territorial birds.