In message <199701120142.RAA11399 at mx.seanet.com> writes:
> I'm hoping someone can recommend good sources of info on the status of the
> Olive-sided Flycatcher. I understand their numbers have declined
> substantially, but I'm looking for specifics. How much has the population
> declined, over how many years, and why? Is there another factor in this
> decline besides habitat destruction (I'm assuming that's the main reason)?
>
> Feel free to respond to me directly.
>
> Michael B. Brown "You don't have to apologise for
> 13406 125th Av. Ct. E. not knowing the names of the birds
>
> Puyallup, WA 98374 and the stones." -Frank Moorhouse
>
> H-206-841-4281 _ _
> W-206-841-8733 (o!o)
> C-206-208-9588 ((___))
> borealis at borealis.seanet.com " "
>
>
>
Michael and Tweeters,

I've observed Olive-sided Flycatchers for over 20 years from Colorado to
Alaska, but to try to deduce any population trends from these scattered
observations is useless. If I did I might conclude that they were on the
increase, because it just so happens I take my students to a place near
Lake Wenatchee where they are fairly common. So for the last six years they
show-up in my field notes more than they use to. One of primary reasons for
conducting the Breeding Bird Survey (BBS) is to look at bird population trends.
The inductive method (collecting specific data and then infering population
trends) involves some math. I'll give the Population Trend data I have for
Olive-sided Flycatcher. These data are from BBSs and are available from a
variety of sources, including The Summer Atlas of North American Birds by
Price, Droege, and Price.


Population Trend (% change)

1966-1993 -48.8*** (764)

1984-1993 -24.5*** (528)

This means that Olive-sided Flycatchers have decreased on survey routes by
48.8 % and 24.5% during the years analyzed. The *** is a probabality measure,
showing how statistically significant the value is. Three asterisks means the
these values have a less than 1% chance of being obtained by chance alone.
Few species show such a decline, thus cause for alarm. For comparison some
eastern warblers have higher values of decline (e.g Tennessee Warbler:
-69.3***).

Hope this helps.
Cheers,
Dan



Dan Stephens (509) 662-7443
Dept. of Biology fax: (509) 664-2538
Wenatchee Valley College e-mail: dstephen at ctc.edu
1300 Fifth Street
Wenatchee, WA 98801