In the last 30 years, the sea gull population has increased significantly in the South Bay -- last year, 46,000 gulls populated this area (compared to just a few hundred in the 1980's). Along with the possible issues this increase has been on local wildlife, it is also affecting San Jose residents. Why these gulls are finding new homes in ponds around the South Bay could be a number of reasons: landfills shooing the birds away or restoration of salt ponds in the area are a couple of the reasons researchers have predicted.
Thankfully, the library isn't having any gull invasions, but we do have lots of materials if you'd like to know more about animal behavior. Animal Migration: Remarkable Journeys in the Wild profiles several species and how they migrate via air, land, and water. Great Migrations is a book companion to the National Geographic mini-series. And for those who are interested in the behavior of gulls, there are several theses from San Jose State University you may like to take a look at.