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Tuesday, December 10, 2013

Leucism in Birds

Two weekends ago I was birding with Peter, Kevin and Klemens at Calvert Vaux Park in Brooklyn. As the afternoon wound down and it got close to sunset, Peter, Kevin and I started heading back to the subway. Klemens, however, decided to stick around and take some more photos. That night he sent me photos of a very unusual looking bird he discovered after we left.

At first glance one might think that this is some vagrant exotic species, like a White-faced Robin, or somebody's escaped pet, but it is neither. It is actually the very common Dark-eyed Junco. The white patches on this bird's face is the result of a genetic condition known as leucism, which is not that uncommon in birds. Over the two plus decades that I've been observing birds I've come across numerous interesting individuals that have caused me to scratch my head a bit before finally figured out the bird's identity.

So what exactly is leucism? Simplified, it is a defect in pigment cells that results in either all cells failing to develop or just patches of body cells incapable of making pigment. This is very different from albinism, which results in the reduction of melanin production. Albinistic animals are easily differentiated from leucistic individuals by their pink eyes. It is interesting to note that albino birds are rarely seen because the lack of melanin in their eyes cause vision problems, usually leading to a very short lifespan. The website "Avian Genetics" has a brief comparison of the two conditions here.

Below are a few of my favorite leucistic birds over the years:

I was at Jamaica Bay Wildlife Refuge with my friend Steve Nanz when we spotted this distinctive gull standing at the edge of Grassy Bay. This was nearly 10 years ago and neither one of us had much experience with rare gulls (which we assumed it was). Returning to the visitor's center, I spotted Kenn Kaufman walking towards his car. I thought, great, if anyone would know what this gull is, he would. Kenn is very modest and his first comment was, "Well, I'm no expert." Yeah, right. He studied the image in Steve's viewfinder for a moment then suggested that perhaps it was a leucistic Laughing Gull. That night I posted a question and the image on the excellent, but now defunct forum called "Frontiers of Bird Identification". By the end of the week the general consensus was just as Mr. Kaufman suggested.

Unlike the gull, this one isn't too difficult to figure out. What is truly amazing about this American Robin, though, is that he returns every year to Prospect Park in early Spring to breed. I first photographed him in 2008. To my knowledge, he was last seen near his territory next to the Upper Pool in 2012. I wasn't aware that robins had such a long life expectancy. I can't recall how many times I was approached by non-birders to ask me a question about "an unusual bird that looks sort of like a robin", but I always knew exactly who they were referring to. If anyone has seen and photographed him in 2013, let me know. Leucism seems to be fairly common in robins, just check out the results of this Google search.

In 2005 I went birding out at Jones Beach with Sean Sime and Joe DiCostanzo. While scanning a flock of Yellow-rumped Warblers next to the Coast Guard Station we spotted this white-headed bird. (Sorry about the quality, I digiscoped it through my bins.) To my eyes, it looked like a Snow Bunting, but acted like a warbler. Had I not been with these two, very experienced birders, I probably would never have figured out that it was a Yellow-rumped Warbler.

I find it fun spotting something out of the ordinary within our local bird populations, even if it is just a leucistic individual. On Brooklyn's Prospect Lake we also have the added challenge of sorting through a growing number of hybrid/leucistic waterfowl.

If you have any pics of leucistic birds that you'd like to share, I'd love to add them to this collection.

Check out Ryan's great pic of our favorite robin taken this past Spring.

1 comment:

Ryan M said...

Here is your leucistic robin buddy alive and well in April of 2013, right by the upper pool, as you would expect:

My aunt speaks fondly of a leucistic cardinal that's been coming to her feeder on Long Island for a few years now. I will have to try to get a picture one day

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