Subject: BIRDXXXX highlights (fwd)
Date: May 26 17:20:12 1994
From: David A Rintoul - drintoul at KSU.KSU.EDU


The following is a regular monthly feature of the _Prairie Falcon_,
the newsletter of the Northern Flint Hills Audubon Society in
Manhattan KS. Other articles and poems from this newsletter can be
found on the Internet (courtesy of Jack Siler) at the gopher server

simon.wharton.upenn.edu

Look in the Bird Things section under the subheading Newsletters.

Or on the WWW server at:

http://compstat.wharton.upenn.edu:8001/

using Lynx, Mosaic or Cello or other appropriate web client software.
--
Dave Rintoul Internet: drintoul at ksu.ksu.edu
Biology Division - KSU Latitude 39.18, Longitude -96.34
Manhattan KS 66506-4901 Compuserve: 71634,32
(913)-532-5832 or 6663 FAX: (913)-532-6653

-----burning birding questions 06/94-------

Birding questions asked anonymously will be answered by the anonymous
answer person. Send your burning questions to the Prairie Falcon
editor, Dave Rintoul, Ackert Hall, Biology Division, KSU, Manhattan KS
66506-4901; or call him at 537-0781 (home), 532-5832 (work), or send
them by e-mail to drintoul at ksu.ksu.edu (Compuserve 71634,32). All
questions are appreciated (even though you might not appreciate the
answers), so keep those cards and letters coming in!

1. Since we are talking about nectar-feeders and the soon-to-be
arrival of the first hummingbirds to the N.E., I have a question for
other birders. I've heard (on good authority) that cool weather
really hurts the hummers, especially the early birds. I was told that
they can become torpid (i.e. "faint") in the middle of feeding if they
get too cold. Because of this problem, it was recommended to me that
one should remove the little perches on the nectar-feeders. This
would force the birds to keep flapping away while feeding thus
producing enough body heat to thwart the early morning cold. Is this
true? Should I remove the perches from my feeder(especially early in
the season)? If it is true, why do the bird-feeder makers still put
little perches on their feeders when they know it could hurt the
birds. Thanks for any info on the subject; I don't want to be the
cause of fainting humming birds.

Far from hurting hummingbirds (and other species like swifts,
swallows, chickadees, even snowy owls!), torpor is an adaptation that
helps birds survive low environmental temperatures. Birds do not go
into torpor while active. They do not "faint" in mid-air, crashing in
a stupor to earth. So don't worry about the perches on your
hummingbird feeder (why are there perches on hummingbird feeders
anyhow; I've seldom seen perches on flowers). Birds go into torpor
during non-active periods, typically at night, but not always. During
torpor, the body temperature falls below normal operating limits,
which decerases the amount of energy necessary to maintain a higher,
normal body temperature. At a new lower limit the birds begin
actively regulating again, but since the gradient between their body
temperature and the environmental temperature is now less, they need
less energy to survive. Indeed, they can make it through until they
can begin feeding again. For hummingbirds, torpor is often a daily
experience (some species of hummingbirds nest near tree-line in the
mountains of the western hemisphere). It is not an unusual event in
their lives.

2. For several weeks now, and especially this last week of March, the
juncos in our backyard woods in the Indiana Dunes have been very
aggressively engaging in chases. But this is their winter home only;
they are going to fly north to breed. So why are they fiercely
chasing each other now, and *here*, where it wouldn't do them any good
to establish territories because they are about to leave and breed
elsewhere?? If they are doing this not to establish territories but
to establish dominance, does this imply that the whole group now
living around our house will all fly north together to exactly the
same breeding area, so that the heirarchy they establish here will
still work in their new joint home??

No, they will not all fly together because as your fellow Hoosiers
down in Bloomington have demonstrated, there is segregation by age and
sex in dark-eyed juncos with the females wintering father south than
either the males or the juveniles. And no, the hierarchy is not for
future worth; the hierarchy works quite well in the here and now. By
this time in the early spring, food sources for granivorous birds are
getting scarcer and there is some immediate value to a dominant bird
in obtaining first choice of what is left. An alternate explanation
(which may well serve the previously suggested hypothesis as well) for
the increase in aggression that you have recently noted may be a
simple reflection of the increase in testosterone levels. This change
results from day lengths becoming long enough to overlap the circadian
period of photosensitivity so that the hypothalamic-hypophyseal-gonad
axis is experiencing its vernal resurgence.

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