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)




On 7/5/06 10:30 PM, "Wayne C. Weber" <contopus at telus.net> wrote:

> Kelly and Tweeters,
>
> Even if the occasional Common Nighthawk is captured by a
> Peregrine, I am quite certain this is not a significant factor in the
> decline of nighthawks.
>
> The decline of Common Nighthawks, from a status of common in the late
> 1960s and early 1970s to rare today, has occurred over a huge area.
> The decline covers, at a minimum, south coastal BC and all of
> Washington and Oregon west of the Cascades. Most of this area
> has NO nesting Peregrines. (E.g., in Greater Vancouver, with well over
> 2 million people and formerly hundreds of pairs of nighthawks,
> there were and are no breeding Peregrines.)
>
> Declines in flying insects are often suggested as a reason for the decline
> of Nighthawks. However, I know of no evidence for any such declines.
> As Stan Kostka has pointed out, other species (e.g. swallows) that
> depend on flying insects have shown no sign of declines-- if anything,
> just the opposite. Yes, "biological insecticides" such as Bt
> (Bacillus thuringiensis) have been used in efforts to control gypsy moths
> and possibly other insect pests. However, these control efforts have
> occurred in very local areas. The strains of Bt used normally affect
> Lepidoptera only-- not all insects. And, for a number of reasons, any
> local declines even in Lepidoptera are unlikely to persist for than 2-3
> years
> if a Bt application is not repeated in later years. (I have done extensive
> research on this subject.)
>
> The fact is, we simply don't know why Common Nighthawk populations
> have declined so dramatically over such a huge area. However, it is very
> unlikely to have anything to do with either Peregrines or Bt.
>
> The theory that increased predation by crows is the main factor in the
> nighthawk decline makes more sense to me than any other theory.
> At least in my area-- Greater Vancouver-- crow populations have increased
> by a factor of at least 4 since 1970. Crows are effective and tireless
> predators of bird eggs and newly-hatched young. I'm sure that a number
> of species have suffered from the proliferation of crows, but
> nighthawks seem to have suffered the worst.
>
> Hypotheses make a poor substitute for documented facts. However, it's
> difficult to study the reasons for the decline of a species which is almost
> gone (west of the Cascades). We should have been studying Nighthawk
> breeding biology 20 years ago, when they were declining but not yet
> gone in our cities.
>
> Fortunately, as noted both by Tweeters subscribers and by me in my travels
> around western WA, Nighthawks actually seem to be increasing a little
> in the last few years. I see them most often in and near clearcuts in
> rural areas, but often not far from the big cities (e.g. in Kitsap Co.)
> Maybe the crows haven't found those areas yet, or the nests are too well
> concealed. Even though clearcuts will not be the salvation of Spotted Owls,
> Marbled Murrelets, or many other species, perhaps they may help to
> prevent Common Nighthawks from completely disappearing from
> our area. So let's just be glad that clearcuts have some wildlife value,
> rather than none at all, as some of us would like to believe.
>
> Wayne C. Weber
> Delta, BC
> contopus at telus.net
>
>
>
>
>
>
> ----- Original Message -----
> From: "Kelly McAllister" <mcallisters4 at comcast.net>
> To: <tweeters at u.washington.edu>
> Sent: Monday, July 03, 2006 8:44 PM
> Subject: Re: [Tweeters] RE: Nighthawks - ? The Kevin Li Memorial
> NighthawkRoofTrail?
>
>
> Interesting, as always, Stewart.
>
> I wonder if peregrines take many nighthawks. There are some birds that
> peregrines really get the best of, on a regular basis. Homing pigeons and
> Rock Pigeons both come to mind. Bufflehead seem to be taken frequently.
> Nighthawks are definitely agile in the air, perhaps too agile to be regular
> peregrine prey. On the other hand, their habit of flying about in wide open
> spaces might make them vulnerable.
>
> I was just trying to think of alternative "limiting factors" besides nesting
> habitat and crows. Certainly, changes in abundance of flying insects might
> be another. Can you say Bt?
>
> Kelly McAllister
>
>
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