Dennis,

I have enormous respect for your knowledge and your accomplishments
as a scientist. However, I find some of your comments about declines
of birds and insects to be disturbingly unscientific and poorly-documented.

I do not disagree with you that the net effect of human population growth
and development on biodiversity is negative. If even a few species of
birds or insects disappear from a large area, that is a bad thing and a
cause for great concern. This is certainly happening in North America
and elsewhere.

However, your statement that "we're making the world worse for birds and
other wildlife, except for a select bunch of species that are
adapting very well to the conditions we create ..." strikes me as
inaccurate and alarmist. For birds at least, there is a large number of
species, not a small number of species, which have increased in
abundance as a result of human-caused habitat changes. I can provide
documentation for this statement.

For birds in North America, one of the best indicators of population change
is the Breeding Bird Survey, sponsored by the US Fish & Wildlife
Service-- a project which includes numerous TWEETERS subscribers
as participants. I looked at the latest summary of bird population changes
in Washington on the BBS website, for the period 1968 to 2004, based on
results from more than 90 BBS routes. These results indicate that,
for 199 species included in the table, only 78 have shown population
declines over this long time period, while 121 have shown increases.

It should be emphasized that most of these "increases" and "decreases"
are small, and are not statistically significant. However, even if one
restricts
comments to species that show statistically significant changes, in
general the BBS shows as many species with increases as with
decreases.

Let's look at the 3 species you specifically mentioned-- Violet-green
Swallow, Barn Swallow, and Vaux's Swift. It may be that all 3 of these
have significantly decreased in your neighborhood, or even in greater
Seattle overall. However, this does NOT mean that they have all
decreased statewide. You may be unreasonably extrapolating from
your own local area to a much larger area.

Barn Swallows have definitely shown a major long-term decline in
Washington, which is evident also in BC and probably in other nearby
areas. For the period from 1968 to 2004, Barn Swallow populations
have declined at a rate of 3.2 percent PER YEAR, which is
statistically significant at the 95% level-- a shocking rate of
decrease. (However, there are still an average of 17 Barn Swallows
seen per BBS route-- they aren't extinct yet.)

On the other hand, Violet-green Swallows have INCREASED statewide
at an average rate of 2.0% per year. At the 95% rate, this increase is
not statistically significant, but it is significant at the 90% level.

Vaux's Swifts show a small decrease-- 0.7% per year-- which is not
statistically significant, and may not be real.

So of the 3 bird species about which you expressed concern, one
is definitely decreasing, one is increasing, and the third shows
no significant population change at the statewide level.

I frequently hear from various long-time birders that Species X or
Species Y, or birds in general, have dramatically decreased over
the last 30, 40, or 50 years. However, I attribute many (not all)
such comments to over-generalization based on a very small local
area, or even to a faulty memory about "the old days". The role
of declining hearing, at least, in older birders should also be
taken into account. This almost certainly does not apply to your
swallows and swifts, Dennis, but many supposed "declines" of birds
described by older observers are a result of declines in their hearing,
NOT declines of the actual birds.

So Dennis, if you expect to convince us of the reality of some of these
supposed declines, please provide better evidence in future!


Wayne C. Weber, Ph.D.
Delta, BC
contopus at telus.net





----- Original Message -----
From: "Dennis Paulson" <dennispaulson at comcast.net>
To: "Tweeters" <tweeters at u.washington.edu>
Sent: Friday, July 21, 2006 7:53 AM
Subject: Re: [Tweeters] insects and swallows


Like Diann MacRae, we have lost the Violet-green and Barn Swallows
and Vaux's Swifts that we would see just about daily over our house
when we first moved in here 15 years ago. I occasionally see all
three species, but very infrequently now.

It's worth considering that these species have declined (also)
because of loss of nest sites or nest material, subtle but continuous
changes that would be very difficult to monitor (just like insect
abundance). Violet-greens need crevices - maybe there are fewer all
the time. Houses are being replaced by condos, which perhaps are very
well sealed against the outside world, as are the houses being built
currently. Barn Swallows need mud, as well as ledges, and I've often
thought that mud is surely declining in urban areas, as our
surroundings are tidied up. I think both of these species have
declined all over Seattle since I've lived here. Vaux's Swifts need
either snags or chimneys, and the former may well be decreasing,
especially of the size needed by the swifts, while fewer and fewer
chimneys may present nesting opportunities because of the way they
are constructed.

It's fascinating to read the accounts of insect abundance by
different contributors, reporting disappearances, declines,
abundances, "too many." I would say that insects have not changed in
abundance in my yard in 15 years, but there weren't many to begin
with. Because of my long time spent in the East, as well as recent
visits in summer, I will reiterate that "bugs" back there are 10x as
abundant (and at least several times as diverse) in forested habitats
as they are in forested habitats in the western Washington lowlands.
In any little sunny clearing back there, you could catch or
photograph insects for several hours and not begin to exhaust the
species present, whereas around here I see the same small number of
species again and again. I see in my wooded "natural" yard pretty
much the same list of 30 or so insects and spiders that Christine
Southwick reported in her Shoreline yard (and thank goodness there
are at least that many), but I consider it a woefully inadequate
representation of biodiversity, when you realize there are 91,000
described species of insects in the US. I'm sorry I haven't had the
time or foresight to make a continuing collection of all the insect
species in my yard, and that would be a great project for an urban
entomologist anywhere.

But that's a digression; the same things are happening continentwide
and worldwide. Basically, we're making the world worse for birds and
other wildlife, except for a select bunch of species that are
adapting very well to the conditions we create as we destroy natural
habitats and replace them with human habitats. If we understood all
the variables, what we see happening is probably quite to be
expected. It should be relatively easy right now to predict which
North American birds will still be common in 50 or 100 years!
-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson at comcast.net