Hi all,
FYI, of course this is not applicable to finding rarities;-)
Alan
http://www.smh.com.au/news/national/when-chips-are-down-health-of-
urban-gulls-takes-a-dive/2007/07/03/1183351209783.html
THE seagull may seem ravenous, but don't give it a chip.
Research shows that, as in humans, silver gulls supersizing on junk
food are the poorer for it.
Urban silver gulls are fatter and less successful breeders than their
counterparts living a wilder life, the Animals and Society conference
will be told this week.
Heidi Auman, an ornithologist, believes these findings, among the
first to examine the physiological effects of human food on urbanised
birds, could be behind a fall in a gull population she studied. And
they may have implications for other species that live on people's
scraps.
Flocks of gulls quickly descend on stray fast food around our cities.
The birds also swarm across city rubbish tips, which Ms Auman said
provided more junk food equivalent for these "garbivores".
In her doctoral thesis, the University of Tasmania scientist compared
birds at two remote sites in the Furneaux Group of eastern Bass
Strait with a colony on the shore of the Derwent River in Hobart.
"The remote birds take flight away from you, whereas the urban birds
practically sit up and beg," she said.
There were physical differences too. "Urbanised gulls had greater
body condition and were heavier than their non-urbanised
counterparts. Across the genders, this meant a mass - or size -
difference of about 10 per cent."
But Ms Auman said the most significant part of her research was the
difference in egg quality. Furneaux eggs had a greater yolk mass,
were larger and heavier.
"The Furneaux egg clutches averaged 42.6 grams, while the Hobart
gulls averaged 41.3. It doesn't sound like much, but it's
significant. With gulls particularly, a high quality clutch means a
higher hatch rate and healthier egg.
"Urban gulls have a greater access to protein and fat. Normally
that's a good thing, and they ought to be producing better eggs. But
this was not true. So it leads to concern about the quality of food
rather than quantity."
Hobart's silver gull population is in decline, and it is possible the
poorer diet may be one reason, along with better management of
rubbish tips and greater competition from other larger gulls.
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Alan McBride
Birding Guide +
http://web.mac.com/amcbride1
Be green and read from the screen
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Skype me: mcbird101
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