Yesterday evening, 8/25, at about 6:40, as we were eating dinner
outside in our yard (which is full of ash and apple trees, so that
not too much sky is visible), we saw maybe 30-40 nighthawks and
50-60 swifts migrating together. Not that they were "one happy
family," for clearly the swifts were flying with and, if it's fair
to say, however subjective it seems, relating to one another, as
were the nighthawks. There were groups of swifts, groups of night-
hawks. Yet these groups mingled. This observation lasted about
five minutes and was, needless to say, thrilling to see. What else?
The swifts were chittering, the nighthawks silent--a difference I
have observed previously. There must have been many more birds in
this "flock" than we observed, given the tree cover. Needless to
say, the nighthawks were out and about much earlier than their
usual dusk feeding time (they breed here in Ann Arbor, especially
on downtown roofs). Since moving to Michigan over 15 years ago,
I have seen this phenomenon of evening nighthawk migration a
number of times, and have twice (now) observed nighthawks migrating
south "with" swifts.

This observation strikes me as interesting insofar as it raises
questions:

(1) Would swifts and nighthawks feed as they go, and, if so, is
or would there be some sort of feeding cooperation?

(2) Since swifts and nighthawks, to my knowledge, otherwise feed
at different times of day, what would explain these birds' association
in migration?

(3) Hence, might their migrating together be a coincidence? It
didn't look like one, but looks can be deceptive.

(4) Finally, since the nighthawks weren't calling, as they do when
they feed at dusk, does this mean that they weren't feeding? Or does
it mean that they don't necessarily call when they feed, but rather
call on territory? (If I owned a copy of Bent, I might know the answer
to this last question.)
------------------------------from Macklin Smith

=============================

From: Nadine Litwin <nlitwin at WEB.APC.ORG>

I have no answers, just the same questions. Here in southern Ontario I have
also noticed nighthawks and chimney swifts migrating apparently together. I
just thought that they were taking advantage of similar flying and insect
needs for migration. And I, too, have noticed the silence of the
nighthawks. I'm wondering mostly about the calls: why do I hear the
nighthawks all through the summer, but not when they're moving?

Nadine Litwin
nlitwin at web.apc.org
Toronto, Ontario, Canada

====================

From: "Coin.Pat" <COIN%NIEHSE.BITNET at ARIZVM1.ccit.arizona.edu>

I noticed this too in Minnesota. As far as I could tell, the peenting call is
given only by birds (only males?) on territory. In early fall I often observed
territorial birds calling and attacking southward-flying silent birds. I
presume the latter were migrants from farther north, where winter starts early.
I love the behavior of these birds, and miss watching them in the summers.
(They are common in MN, but rare here in NC.) Does anybody have any recent
references on their behavior? There is some information in Bent's Life
Histories, but no systematic description of their displays.

Patrick Coin COIN at NIEHS.NIH.GOV
Durham, NC

==========================

From: PJOHNSON at COE.ENG.UA.EDU

Driving home from dinner last night I noticed some nighthawks circling
through the lights above a billboard alongside the river. The top was down
on the car, and Toni was driving, so I was able to to get a good look as we
sped past. There were at least 50 birds ghosting in and out of the lights
and the effect was quite lovely. Of course, I then looked a every billboard
on my way home (at least 20 more), and did not see a single additional bird.

Is flocking behavior preparatory to migration? They don't seem to be
migrating in ernest here, for, as we entered the restaurant earlier in the
evening we had stopped to listen to single birds buzzing. And then over
dinner we watched a pair of them dogfighting outside the restaurant window.
(Yes, there were swifts also, but before dark we saw no flocks of either
bird).

Philip Johnson
Tuscaloosa, AL
pwjohnso at coe.eng.ua

========================

From: Alvaro Patricio Jaramillo <jaramill at SFU.CA>

Macklin Smith asked:

> This observation strikes me as interesting insofar as it raises
> questions:
> (1) Would swifts and nighthawks feed as they go, and, if so, is
> or would there be some sort of feeding cooperation?

My experience is that they do feed as they go. Back in Toronto I lived
right on their migratory path and saw hundreds, if not thousands every
August. I frequently observed them feeding on "alate" ants that had emerged.
These hatches are biggest after rain and nearing the full moon. Usually the
nighthawks and swifts were accompanied by flocks of Ring-billed Gulls also
feasting on the ants. Here in Vancouver, nightawks and swifts are not nearly
as common as back east, but I have noticed that numbers of migratory nighthawks
correlate well with hatches of "alate" termites.

I doubt that there is any cooperation between the nighthawks and swifts, they
just happen to share similar foods, and similar migratory "flyways". In Toronto
, the peak of migration of the swifts was a little later than the nighthawks if
I remember correctly. Often the swifts kept going right into October, much later
than the last nighthawk.

> (2) Since swifts and nighthawks, to my knowledge, otherwise feed
> at different times of day, what would explain these birds' association
> in migration?

My guess is a mix of several elements, such as a)taking advantage of when
food is most plentiful. b) avoidance of obstacles such as water bodies. c) both
being drawn to areas of particular insect abundance, "hotspots". As I am writing
this, it occurs to me that most swifts and at least one other species of
nighthawk (the Nancunda Nighthawk) tend to forage in flocks when not breeding,
and sometimes while they are breeding. Flock foraging may actually be efficient
if these insect hotspots are local and patchy, the flock may be better at
detecting a hotspot than a lone foraging individual perhaps. The other side of
the coin would be that the flock forms around the hotspot, maybe by the indivi-
dual that finds the hotspot communicating the information to others. So I
take it back, maybe they do cooperate in some way. I imagine that very little
work has been done on foraging swifts or nightjars.

> (3) Hence, might their migrating together be a coincidence? It
> didn't look like one, but looks can be deceptive.
> (4) Finally, since the nighthawks weren't calling, as they do when
> they feed at dusk, does this mean that they weren't feeding? Or does
> it mean that they don't necessarily call when they feed, but rather
> call on territory? (If I owned a copy of Bent, I might know the answer
> to this last question.)

I seldom hear nighthawks calling after about the middle of August, this is
probably because the calls are associated with the breeding season, but I am
taking a guess. I have never heard Common Nighthawks calling in the wintering
grounds in Argentina either, but I have seen few flocks down there.

Al Jaramillo
jaramill at sfu.ca
Vancouver, B.C.

=======================

From: Susan Hazelwood <SUSAN at IMED.MISSOURI.EDU>

The migration of common nighthawks has moved to south central
Missouri (Dent county) as of last evening. I was driving home
from a day float on the Current River when out of the dusk and
low hanging clouds I saw numerous cm nighthawks -- one here and
one there and another further over. I could see them through the
open sunroof and out the windows. The sighting lasted for over
10 miles, until there wasn't enough daylight left to see birds
any longer.

No, I didn't stop to listen to see if they were calling. BTW,
there were no chimney swifts with this flock -- unless the clouds
were so low they obscured them. I liked Philip Johnson's
description of "ghosting in and out" because that is what I too
experienced. Very ephemeral.

Susan Hazelwood
Columbia, MO
Susan at IMed.Missouri.Edu

=========================

From: "Jean M. Hoffman" <fb704 at CLEVELAND.FREENET.EDU>

> Driving home from dinner last night I noticed some nighthawks circling
>through the lights above a billboard alongside the river. ----deleted---
>
>Is flocking behavior preparatory to migration? ----deleted---

Every year from the latter part of August to mid September we go a couple
of times a week after dinner to a local church with a very tall,
illuminated tower to watch feeding Common Nighthawks. There are often only
a few, but sometimes there may be 20 - 30 silently sailing around the
tower, in and out of the surrounding darkness. Once we have seen this
after hearing one before dark, but otherwise they have been silent. Here
along Lake Erie we see migrating birds, sometimes in groups totalling 100 -
300 birds. Normally this is in the evening, but before dark. Other times
they are apparently moving in mid-day. Chimney Swifts are active at the
same time, but I have never connected the movements of the two species.

Jean Hoffman
Cleveland Heights, OH
fb704 at cleveland.freenet.edu