Tweeters,

Jeff Gilligan makes a good point when he talk about the loss of
flat gravelled rooftops as nesting sites for Common Nighthawks.
In the Vancouver, BC area, as well as the Portland area, this
was probably the main type of nesting site used by nighthawks
30 or 35 years ago.

However, in the Vancouver area, not all the nighthawks nested on
rooftops, by a long shot. I would guess that about 70% of the
population used rooftops (and yes, there are still some suitable
rooftops out there). The other 30% or so nested on the ground,
mostly on sandy/gravelly soils in the Fraser Delta, in such places
as Iona Island, Sea Island, and Boundary Bay.

The ground-nesting nighthawks have disappeared around
Vancouver just as thoroughly as the roof-nesting ones. So
it looks to me that although loss of nesting sites may be a
minor factor in the disappearance of nighthawks, increased
avian predation is the main factor.

Although I pointed the finger at crows (as have many others) as a key
factor in nighthawk declines, Glaucous-winged Gulls may also be
a significant factor in areas close to salt water (e.g. downtown
Vancouver and the University of BC area). Gulls nest on rooftops
in some of these areas, and like crows, they have increased in
recent years, and are very effective predators of bird eggs and small
chicks.

Despite comments by Dennis Paulson and others, I am not aware
that anyone has even attempted to measure changes in the numbers
of flying insects in the Pacific Northwest-- at least, insects of the
kinds that Common Nighthawks would eat. (But then, I am not an
entomologist and I do not read entomological literature.) At least,
we do have some very concrete evidence that numbers of avian
predators such as crows and gulls have increased.


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




----- Original Message -----
From: "Jeff Gilligan" <jeffgill at teleport.com>
To: "Wayne C. Weber" <contopus at telus.net>; "Kelly McAllister"
<mcallisters4 at comcast.net>
Cc: "Tweeters" <tweeters at u.washington.edu>
Sent: Thursday, July 06, 2006 12:49 PM
Subject: Re: [Tweeters] Peregrines vs. Nighthawks?


I haven't read all of the posts regarding the decline of Common Nighthawks
in western Washington, but I can comment regarding one possible reason for
the species' decline in the Portland area.

Until about 30 years ago the species was found in limited numbers (although
easily detected) throughout urban Portland. Downtown Portland seemed to
have the highest concentration. Night baseball games at then Multnomah
Stadium were typically enhanced by nighthawks feeding around the outfield
lights. Nighthawks regularly flew over the northeast Portland house where I
grew up, and were were a delight to hear when I left my second floor bedroom
window open at night.

Some time around 30 years ago the practice of having pebble (or crushed
rock?) on the top of flat (or "built up" roofs as they are called in
Arizona) was changed to the use of some kind of flat spread-on synthetic
material. The nighthawks reportedly had nested on the on the rock covered
flat roofs - which approximated gravely river shores. Being on the tops of
buildings also apparently was a safe place to nest - at least from mammalian
predators. With the loss of that habitat there was apparently almost no
habitat to replace it in Portland. I do not recall nighthawks ever being
common in the Portland area outside urban Portland, with the exception of
seeing several at a new clear-cut on Larch Mt. - about 20 miles east of
Portland. I did see an occasional nighthawk elsewhere in the Portland area
though.

In the past 30 years I have only seen or heard Common Nighthawks twice in
Portland, both in the Laurelhurst neighborhood in northeast Portland. Both
occurrences were at times where I presumed the birds to be migrants. From
the office that I occupied for years in southwest Portland I was able to see
most of the roof tops of an extensive area of blocks, from Portland State
University well to the north and west. None of the flat roofed buildings
that I could see have rock covered roofs.

Although I think that there are now enough Peregrine Falcons to take care of
themselves without human intervention, I doubt that peregrines have been
much of a factor in the decline of nighthawks in the Portland area. The
decline began before the increase in Peregrines, and in the Portland area
nighthawks rarely came out before dusk.

Jeff Gilligan (Portland, OR and Nahcotta, WA)