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Wednesday, March 12, 2008 01:40 am

Winging it

At least 18 species of gulls have been spotted on Lake Springfield

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A ring-billed gull
PHOTO BY H. DAVID BOHLEN
Untitled Document They may look like little blizzards, but those fast-moving cloudlike formations over Lake Springfield aren’t precipitation. They’re gulls, flying low over the water. There are 51 identified species of gulls in the world — 28 in North America — and Springfield has played host to at least 18 of them.
Telling species apart can be quite difficult. Variations in plumage can be subtle, with whites, grays, browns, blacks, and occasional pinks. Adding to the complexity, variations within a species can be dramatic, depending on a bird’s age and hybrid can occur. To correctly identify a member of a species, an observer must analyze the bird’s size, shape, color of the back, wingtips, tail, legs, eyes, and bill, as well as recognize the pattern on the wings, tail, and underparts. Figuring out the stage of molt — when birds drop their old feathers and grow new ones — sometimes helps. One does not merely look at gulls, one studies them. People who specialize in studying gulls are known as larophiles. Around here we’re a diverse group, including a firefighter from St. Louis, a schoolteacher from Belleville, and a grocer from Peoria. Of the 18 species that have been recorded here, three are the most common, although none nests here. Ring-billed gulls, the most numerous, are present throughout the year but they are very migratory, and only a few immatures stay for summer. They nest as close as Chicago near Lake Michigan. Practically all of the species, save a few immature birds, leave during the summer. The larger herring gull frequents Lake Springfield mostly in the winter, and the much smaller Bonaparte’s gull stops by during migration. Bonaparte’s gull nests, oddly, in abandoned songbird nests in open coniferous forests.
Most gulls come to Lake Springfield during periods of maximum ice, making gull-watching even more difficult. At times my telescope is so cold that it sucks the heat from my eye, fogging the objective lens. But the dead of winter is also a time for rare sightings. One such memorable occurrence took place on Jan. 1, 1991. I was slipping and sliding on the ice near the dam when I spotted an unusual gull flying fairly low toward me. In my haste to stop, I slipped and fell on my back. With no time to get up, I raised my binoculars while still on my back, just in time to see an immature ivory gull gliding over me. It flew out to Lake Springfield and landed on the edge of the ice. I joined several other observers, and we watched, photographed, sketched, and took notes on the rarest bird ever recorded in Sangamon County. At the time, this was the southernmost point at which an ivory gull had been seen. These birds usually stay in the Arctic, where they follow polar bears, eating bear dung or the scraps of seals the bears have killed. The ivory gull is more at home on the Arctic ice floes than in the relatively warm environs of central Illinois, and it soon left. Thayer’s gull epitomizes the shades of difference displayed by gulls. Once, in the early 1970s, it took me two days to identify one. Fortunately improvements in field guides — some devoted only to gulls — and the Internet make identification easier. Even gull taxonomists cannot decide whether it is a full species and, if so, whether it is more closely related to the herring gull or the Iceland gull. Part of the problem is that these birds breed north of the Arctic Circle and studying them in their nesting colonies presents logistical nightmares. In December 2007 I found a large northern gull with white wingtips, called the glaucous gull, in its first-year plumage. It had apparently hit one of the many high wires crossing Lake Springfield, for it had a bloody spot on its right wing and could not fly. The gull steamed around the lake for several days and then disappeared, perhaps into a cove. Then, on Jan. 3, the day of the Springfield Christmas Bird Count, I saw it first thing in the morning, sitting on the ice with other gulls north of the beach house. Later that afternoon I decided to see whether it was still there. It was — but it was the only gull there, because adult bald eagles were standing on either side of it. Avian predators such as eagles make frequent passes over flocks of waterfowl and other birds to find those that cannot fly or do not attempt to get away. If they spot an incapacitated bird, they will single it out and try to kill it for food — I had watched some eagles kill and eat a herring gull a couple of weeks before. These eagles had cut the glaucous gull from the flock, and I watched through my 60-power scope what I thought would be a fight to the death out on the ice. One eagle stood in the gull’s way, making sure that the gull did not walk away; the other eagle was the aggressor. It flew over and grabbed the gull and threw it a few feet. The gull slid on the ice but took the abuse stolidly. Then the eagle flew and hovered just above the gull several times — but the gull pointed its fairly large bill up at it, and the eagle backed off. Predators cannot afford to have their wings or feet injured, because they use them in hunting and cannot survive without them. The aggressor eagle walked and slid over to the gull, flew up and grabbed the gull’s head with its talons, and flapped higher with the gull dangling by its head. I thought that this would be the end, but the gull started biting the eagle’s feet and the eagle let go, dropping the gull back to the ice. Several variations of this attack took place over the next several minutes, at which time I took the opportunity to digiscope some long-distance photos. The nonaggressive eagle flew off. The other eagle stood for what seemed like a long time and glared at the difficult gull, which just sat there as if trying to ignore the eagle. Finally the second eagle flew away as well. I thought that perhaps the eagle had punctured the gull’s body cavity with its huge talons and that it was going off to wait until the gull became weaker and then come back. I had to leave to continue my bird count, but the next day I was there at first light, and the glaucous gull was still sitting on the ice, none the worse for wear. I saw the gull for several days after that — still alive — the fighter of eagles! The next time you cross the dam at the lake and you see the “blizzard,” know that the world is an extremely varied and complex place. I hope that it will always be that way.
H. David Bohlen works in the zoology department of the Illinois State Museum.
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