NY Times suggests that CO2 caused an island's gull population to drop by half in 10 years

Scientists in Washington State Adopt Tiny Island as Climate-Change Bellwether - NYTimes.com

Among the declines the researchers are noticing: historically hardy populations of gulls and murres are only half what they were 10 years ago, and only a few chicks hatched this spring. Mussel shells are notably thinner, and recently the mussels seem to be detaching from rocks more easily and with greater frequency.
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During a research trip in 2000, Dr. Pfister and Dr. Wootton first began testing the pH of water samples. They found the water around Tatoosh and along nearby coastlines to be 10 times as acidic as what accepted climate change models were predicting. Even after collecting seven years of data, when they published their findings in the Proceedings of the National Academy of Sciences in 2008, their data were met with skepticism.

Controlling gull damage

In the Great Lakes region, the number of ring-billed gulls has been increasing at about 10% per year since the early 1970s. Bent (1947) said of it, “the ring-billed gull yields readily to persecution, is easily driven from its breeding grounds and seems to prefer to breed in remote, unsettled regions far from the haunts of man.” However, a colony on Leslie Spit on the waterfront of Toronto, Ontario, increased from 20 pairs in 1973 to 75,000 to 80,000 pairs in 1982 (Blokpoel 1983). It appears that ring-billed gulls have changed some of their habits in recent years and have adapted to humans in their environment. A colony of laughing gulls in the Jamaica Bay Unit of Gateway National Recreation Area, New York, increased from 15 pairs in 1979 to 7,600 pairs in 1990 (Richard A. Dolbeer, pers. commun.).
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Increasing gull populations in North America during the past century have led to a variety of problems for different segments of society.