An ornithologist at the University of Rhode Island who studies the physiological changes that birds undergo to migrate has found
that the capacity of a bird’s gut to change with environmental conditions is a primary limiting factor in their ability to adapt to the rapidly changing climate. And he believes that most other animals are also limited in a similar way.
Scott McWilliams, URI professor of natural resources science, says that spare capacity – the extent to which animals can modify their physiology to deal with ecological changes – varies from species to species, with some having great capacity to change while others do not.
“It’s all about the time scale over which evolution occurs in relation to the timing of the changes now occurring in the environment, because there are likely to be mismatches,” he said. “Our rapid climate change is happening too quickly for most animals to evolve a response.”
McWilliams and a colleague at the University of Wisconsin measured the spare capacity of white-throated sparrows, a common migratory songbird in eastern North America. He found that birds acclimated to a very cold environment (-29C) were able to eat 2 to 4 times as much food as sparrows acclimated to summer temperatures, although the sparrows could not eat enough to live at temperatures colder than -29C.