I'll add to what Todd Hass wrote that it's in the best interest of the
immature birds not to hang around the colonies, where (a) there is a lot of
competition for the food resource, and (b) aggressive behavior may be
directed toward them by the adults. I remember when we conducted aerial
seabird censuses, we would see a lot of immature Glaucous-winged and
Western gulls all along the coast, but when we got within a mile or so of
one of the nesting islands, not an immature was to be seen! I'm speaking
statistically, you understand; I'm sure there are occasional immatures
around nesting colonies.

Todd was alluding to the error made by many in assuming that what an
individual does is for the good of the *species*. We have essentially no
evidence that this phenomenon, which has been called "group selection,"
drives evolution, and abundant evidence that what an individual does is
good for itself (individual selection). This includes altruistic behavior
such as defending the young, warning siblings about danger, even--in
long-lived animals with good memories such as humans--helping a friend.

To show how easy it is to fall into this error, in the 50s a premier
shorebird biologist tried to explain why adult shorebirds migrate so
quickly south from the Arctic after breeding (why we see them here at the
end of June). He hypothesized that they did this so the resources present
on the breeding grounds would be available for their young. The
alternative hypothesis that they were heading quickly for wintering grounds
to which they were much better adapted and to which they needed to go to
accomplish their annual molt was found to be much more in line with the
facts.

People have tried for a long time to defend group selection, and there are
still some aspects of it that may pertain to populations, but most of what
we see in nature can be fairly readily attributed to the "selfish gene."

Dennis Paulson, Director phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416