G'day all
A couple of days ago I was rambling on about a theory for the declinme of some
of our woodland birds. It had to do with little islands
of favoured habitiat in forests and a birds reluctance to leave one island and
colonise the next one.
Reading the latest New Scientist (3rd Feb) today I came across an article
entitled "Safety in numbers".
It discusses how , for some animal species, undercrowding can lead to
extinction. Apparently a US zoologist
named Warder Allee (1885-1955) studied this in the 1940's but his ideas were
discredited and largely forgotten.
Now, however, "an awareness of these Allee effects looks set to transform
conservation practices."
"Allee effects centre on the observation that some species find it difficult to
breed successfully once the population
falls below a certain number or density"
There are several Allee effects that result from undercrowding:-
Harder to find mates (Blue Whales)
Species where males gather together to stimulate one another for breeding
(Kakapo)
Reduced predator protection (Flamingos, Banded Stilts)
Cooperative breeders finding themselves without helpers (African hunting dogs,
White-winged Choughs)
It is a nice bt of serendipity and I would like to hear the thoughts of any of
the ornithologists on birding-aus about Allee effects.
Please don't get too technical though.
Cheers
Steve
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Steve Clark
Hamilton, Victoria, 3300
HTTP://www.ansonic.com.au/clarks/sw_birds.htm
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