[TN-Bird] Re: species apparently in decline (BBS data)

In a message dated 3/28/03 2:01:27 PM Central Standard Time, 
jwcoffey@xxxxxxxxxx writes:

> North American species apparently in decline according to Breeding Bird
> Survey (BBS) data.
> 

I was hoping someone could answer to the following question. BBS are fixed 
routes run over many years (The above report was just a 10 year period) how 
do they adjust or justify the numbers when there is a tremendous generational 
change in habitat along most routes that I know. Some formally rural routes 
are now settled. Some agricultural routes which once sported wide fence rows 
now are farmed to the fence lines. Generally, farm practices in regions 
change, such as extensive flooded rice fields where there had been cotton or 
soybeans. Tree farms where there had been mixed hardwoods. Once fallow fields 
are grown up in trees. If the exact habitat is not present over these periods 
then the exact birds surely are not present.

I do not deny a decline in many species but of those listed I have seen 
habitat changes shift the concentrations from one location to another. 
Therefore a species can increase or decrease on a route but the species 
numbers stay the same in the area. If you are looking for Red-headed 
Woodpeckers in an area where the prime older woods have been clear cut and it 
is now new growth, you are not going to find them, but 2 miles away in 
another woods that has matured or been selectively cut you will find plenty. 
It's habitat, habitat, habitat. Just as others, I have seen marked increases 
in some of the species listed in my area in the 20 plus years I've been 
birding.

I'm sure they have a mechanism that adjusts for this habitat change but I 
would like to know how it works.

Good Birding!!!

Jeff R. Wilson
OL' COOT / TLBA
Bartlett Tenn.


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