Believe it or not, ring-billed gulls were scarce in Pennsylvania 100 years ago.
Along with many other birds, gulls were killed for their feathers to adorn ladies' hats. Back then their breeding range shrank to the areas uninhabited by humans -- the prairie potholes of the U.S. and Canada.
After the 1917 Migratory Birds Convention Act was passed, it took the gulls a while to recover but by the 1970's they were on a roll. Between 1976 and 1984 their breeding numbers increased 11% per year in the Great Lakes region.
The reason for their success can be summed up in this picture: It's safe to be around people now and gulls are opportunistic feeders. They're more than happy to eat what we eat.
"Get away! This bread is mine!"