(Transcript of For the Birds for January 17, 2012, sponsored by Vickie and Barry Wyatt. Thanks so much!)
Russ and I are headed to Florida for a few days next week, to visit our son and so I can help out with the Space Coast Birding and Wildlife Festival. I love being in northern Minnesota in winter because I truly love chickadees and owls and all our other splendid winter birds, but every now and then it’s lovely to break away and see birds that never make their way north, and when there’s all the cold of winter with none of the snow, I must say I don’t mind wandering south for a bit.
The Florida coast is filled with a rainbow of spectacular birds, but of all the ones I enjoy down there, a few stand out as my favorites. And one of these is the Black Skimmer.
Every time I see skimmers, I’m blown away yet again by their bizarre bill. It’s brilliant orange and black, and the lower mandible is significantly longer than the upper, jutting out well beyond the upper bill in a wonderfully peculiar adaptation that allows them to capture fish in a unique way. Skimmers glide low over the water, usually on motionless wings, their lower mandible tip slicing surface of water. When the lower bill contacts a fish or other object, usually within just three centimeters of the surface, the upper mandible clamps down while the head and neck tuck downward, securing the fish, which is then turned and swallowed headfirst or carried crosswise in the bill to the nest. Skimmers do most of their fishing at low tide, and so may fish at any time of day or night.
From the side, the bill looks thick and bulgy,
but from straight ahead, it is surprisingly flat as a knife.
At hatching, a baby skimmer’s mandibles are equal in length, but by the time it fledges at 4 weeks, the lower bill is already nearly 1 cm longer than the upper.
This kind of unique adaptation seems like all a bird would need to set itself apart from other species, but skimmers have another unique feature. Their relatively large pupil constricts to a narrow vertical slit—something the eye of no other bird species can do. Scientists haven’t settled on the reason why skimmers have this cat-like feature, but it may be an adaptation to protect the retina from the glaring bright light of sun above and sparkling water below, or it may enhance their vision for nocturnal feeding. I personally never noticed this before I read about it in the Birds of North America Online, so I carefully went though all my close-up shots of Black Skimmers. The black eye is so difficult to see against their black head feathers that I had to tinker with the “Fill Light” feature of my photo editing software to fade the iris just enough to see that sure enough, the pupil is a slit. If you click on the next two photos, and then right-click them on Flickr.com, you can view them in a larger size to try to see this cool thing.
Except while fishing, Black Skimmers gather in large flocks. Like most birds, they usually face directly into the wind, which keeps their feathers aligned and unruffled.
A gathering of skimmers is a gorgeous study in black and white and orange whether they’re all standing still, all asleep, all preening, or all flying. Interestingly, they show what’s called contagious behaviors, and you can’t help but notice that if one skimmer is doing something, so are its neighbors, the behavior spreading through the whole flock.
The more I learn about Black Skimmers, the more fascinating I find them, and the more I want to capture each one of their features and behaviors. So whatever else I find myself doing in Florida, I know I’ll be taking photos of skimmers wherever they may be.
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(Production of today’s For the Birds was made possible in part by a generous grant from Vickie and Barry Wyatt.)