hello tweets.

i just received this message and thought you'd enjoy reading it.

regards,

Deborah Wisti-Peterson email:nyneve at u.washington.edu
Department of Zoology, University of Washington, Seattle, Wash, USA
Visit me on the web: http://students.washington.edu/~nyneve/
<><><>Graduate School: it's not just a job, it's an indenture!<><><>


---------- Forwarded message ----------
3/6/00


COLUMBUS, Ohio - Legend says that the early bird gets the worm, but
research suggests that the bird that dines just before going to bed
has the real advantage.

A new study has found that socially dominant birds are generally
leaner than their subordinate peers of the same species, probably
because they can eat when they want and don't face as great a risk of
starvation.

Dominant birds stay lean during the day and then pack on the fat just
when they need it most - before a chilly winter night. Staying lean
helps birds stay more maneuverable during attacks by predators. Lean
birds also have more time during the day to watch for predators,
rather than spending the bulk of their time looking for food.

Natural selection would like to keep a bird as thin as possible, but
also have enough fat to get through the night," said Thomas Grubb, a
co-author of the study and professor of evolution, ecology and
organismal biology at Ohio State University.

By eating late, dominant birds can reduce their risk of predation
without increasing their risk of starvation."

The research appears in a recent issue of the journal The Condor.

Subordinate birds have a less predictable food supply during the day
because they must look for food in places that dominant birds wouldn't
normally bother with, according to Grubb. Also, dominants can displace
subordinates from food.

"It seems that subordinate birds must carry more fat during the day as
an 'insurance policy,' making them more vulnerable to capture by hawks
and other predators," he said.

Grubb and his colleagues used data taken from hundreds of birds of
known age and sex during a 10-year period. They found that, overall,
dominant birds carry less weight than subordinate birds in the same
species.

The researchers used feeding, foraging and body weight data taken from
birds caught alive in central and northeastern Ohio from November
through March 1988 to 1997. They focused on three woodland species:
the Carolina Chickadee, Tufted Titmouse and White-breasted Nuthatch.

In these birds, dominant status depends on gender and age. In each
species, adult males top the hierarchy, followed by juvenile males,
then adult females and, finally, juvenile females.

The researchers associated a bird's body mass to the time of day it
was caught. Dominant birds remained lean throughout most of the day,
while the subordinate birds tended to be heavier.

A bird can gain as much as 10 percent of its total body mass each day
in fat. Gaining fat before nightfall can help birds survive in winter
because they often go into hypothermia as a survival mechanism. Birds
can lower their body temperatures by as much as 42 degrees. (The
average body temperature for these birds was about 104 degrees.)
During the night, birds tend to lose their accumulated body fat.

"Extra fat at roosting time means a bird needs to go less far into
hypothermia at night because it has more energy for metabolism," Grubb
said. "Hypothermia is thought to be a cost, because it makes a bird
less aware of its surroundings, therefore increasing its vulnerability
to nocturnal predators."

Grubb co-wrote the study with Vladimir Pravosudov, a postdoctoral
researcher at the University of California, Davis; Paul Doherty Jr., a
graduate fellow in evolution, ecology and organismal biology (EEOB) at
Ohio State; C.L. Bronson, a graduate research associate in EEOB; Elena
Pravosudov, of the American River College in Sacramento; and Andrew
Dolby, a visiting assistant professor at the University of South
Florida in Tampa.

#

Contact: Thomas Grubb, (614) 292-0329; [9]Grubb.1 at osu.edu
Written by Holly Wagner (614) 292-8310; [10]Wagner.235 at osu.edu

References

1. http://www.acs.ohio-state.edu/units/research/archive/archive.htm
2. http://www.acs.ohio-state.edu/units/research/natnews/
3. http://www.acs.ohio-state.edu/units/cancer/cncrrpt.htm
4. http://www.acs.ohio-state.edu/units/cancer/frontier.htm
5. http://www.acs.ohio-state.edu/units/research/synergy/index.htm
6. http://www.acs.ohio-state.edu/units/cancer/hnbkhome.htm
7. http://www.acs.ohio-state.edu/units/research/scicom.htm
8. http://www.acs.ohio-state.edu/
9. mailto:Grubb.1 at osu.edu
10. mailto:Wagner.235 at osu.edu