Let me start by stating that I do not have a science/biology background, but
I have been studying the owls on Bainbridge Island in the capacity of a
"citizen scientist" since 1995. My "surveys" are less than scientific, as I
do not follow a set protocol for conducting them.

I do however, posses a data base that shows a shift in owl species
populations.



When I first started owling on Bainbridge in 1995, the most common summer
time owl was the Western Screech-owl (WESO). I knew of over a dozen pairs
on the Island. Barred Owls (BDOW) did not find their way to the Island
until 1992, and I did not detect my first until December of 1995 on a
survey. My definition of "survey" was a birding trip out at night with the
purpose of locating owls that involved at least three different locations.



In the interim years, the screech owl population has plummeted here, to the
point where I can't find a screech-owl on the 27 square miles that make up
this Island. Last year was my first year without recording a WESO on the
Island. But I do have at least 24 pairs of BDOW. The human population here
has grown from 16,000 to 22,000, and while substantial , should have had a
more negative impact on large owls than small. It did not.



A few facts about the species here in the PNW, at least on Bainbridge
Island: BDOW lay eggs the first week of March. WESO lay eggs first week of
April. This means that BDOW are out of the nest before WESO, and that adult
BDOW are looking for a food source for young before the WESO are. BDOW here
are bird eaters. Yes, they eat mammals, and are generally opportunists, but
I haven't seen a BDOW nest yet that did not contain bird feathers-
particularly crow. I have even found wren feathers in a BDOW nest. Young
WESO out of the nest beg for food using a call that attracts parental
attention - also BDOW attention.



I have witnessed a BDOW make a pass (unsuccessful) at and adult WESO. I have
also found young WESO feathers in my driveway the morning following warning
"chuck" calls from a pair of WESO when a BDOW arrived.



I propose that the issue is not so much adult predation of WESO by BDOW,
but the inability of WESO to reproduce that is bringing the WESO population
down. Yes, there are areas in Sequim apparently that still have a healthy
WESO reproducing population, but I would suggest that it is merely a matter
of time until a BDOW pair moves in that the population crashes. As Stewart
pointed out, the best thing going for WESO now are the small parks that
can't support a BDOW and would normally be considered a population drain for
most avian species, as these are the areas that WESO can successfully
reproduce in, and get the young to adulthood, without BDOW threats.



There have been several emails that infer that Eastern Screech-owls and
Barred Owls cohabit the same area in relative peace. I have not seen
literature that supports this, though I have not looked for it either. It
could be that eastern BDOW have a mammalian diet rather than an avian based
one. I grew up in northeast Ohio, and while I can remember Barred Owl
around, I never saw or heard an Eastern Screech-owl. BDOW, being the
opportunist that they are, eat anything that moves that is smaller than
themselves, if it does not appear difficult to catch and kill.



-J. Acker

owler at sounddsl.com

Bainbridge Island, WA