When a birder sets out to
spend
substantial
time
studying,
monitoring
or otherwise getting to know
a particular
species,
it
becomes
apparent how little even keen naturalists
know
about
such
species' habits and behaviour.
During the 1980s, I had
the enjoyable
opportunity
to study
a
bird that I knew
(at least through
personal
experience) very
little about.
Even the writings of other naturalists
and
the
experience
of my many naturalist friends were rather spare
in many
details.
I had long had an interest in night birds, and
had always found Whip-poor-wills
particularly fascinating. Never active during the day, singing
loudly and long during the deep twilight and night,
virtually unfindable during the day,
gobbling up flying insects in the dark-all these
mysterious traits made them a challenging and attractive species
to study.
How do slow moving humans with poor night vision
study such creatures? At that time,
radio telemetry was becoming
fairly
sophisticated,
and I made use of this powerful tool
for studying
animal behaviour.
Radio telemetry first requires the placing of a
small radio transmitter of a particular frequency on a free
roaming animal and then involves the monitoring of its activity
using a portable radio receiver.
To use commercial radio parlance,
the animal is a moving
radio station,
and the scientist is a nearby radio.
Male Whip-poor-wills are easy to catch.
(You must have a
CWS
permit.)
By using a mist net and a loud
tape
of
a territorial
song, they are easily lured in and caught.
Females are rarely
attracted in this way,
although I did catch a few.
Once caught,
I placed the radio receiver on the bird. The
receiver was like a little backpack with straps made of elastic
hairbands,
one over each wing,
so that the receiver sat in the middle of the
back with the short antenna extending down the length of the
back.
The whole procedure from the time of capture to
the time of release usually took about 60 seconds.
.
I wanted to monitor Whip-poor-will
nests. Unfortunately, not
only
were
females
rarely
caught
the
way I've
described, the males spent
little
time
on
the
nest,
although
this proved to vary among
birds.
How
many
readers
have
found
Whip-poor-wills'
nests other
than by
accidentally
stumbling
upon
one during
a daytime
ramble
in
the
woods?
Not
many I'm sure.
Whip-poor-wills
have
big
light-catching
eyes that have a reflective retina
designed
to make extra
use
of the light collected.
Most night mammals have the same
and I'm sure everyone is familiar with the resultant eye shine
from
animals seen on the roadside
at night.
We employed this trait to find
Whip-poor-wills'
nests.
Concentrating in areas where we believed
from the male's behaviour the nest might be, we searched the
forest floor at night with powerful
lights.
In order for this technique to work
the
light must be near one's eyes, since the retinal mirror reflects
the light right back to the source.
Wandering the woods at night in this way is
fascinating. With a bright light,
not only can you find the reflected eyeshine of
many mammals, but the eyes of countless spiders and moths fairly
twinkle in the foliage. Nonetheless, this system worked, and we
did find incubating female Whip-poor-wills,
but usually not without a lot
of
effort
and
perseverance.
Once the nest was found,
it was easy
to
flush
the
female
from it and into a mist net for equipping her
with a radio
transmitter.
In
the two summers north of Kingston I studied five pairs and seven
nests. We monitored their movements, their parenting, their
feeding,
their vocalizations and their territorial
responses.
By comparing those data with
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light data (the position of the sun, the position of the moon, the amount of
moon face illuminated),
I was able to draw several conclusions.
Sparing you the numbers and statistics,
Whip-poor-wills function best within certain light levels. Daylight
is too bright and
night
without moonlight is too dark.
They operate optimally during twilight and moon-light.
Singing,
responding to intruding birds (i.e. tapes), feeding
the young, foraging,
and moving about their territory are all concentrated
during these periods.
During the dark part of the night, they are generally
quiet and still,
although less so than during the day.
This means that during the period of the new moon,
Whip-poor-wills must accomplish virtually everything they have to
accomplish between dawn and dusk,
a period of about three hours.
I also collected dozens of nest records of
Whip-poor-wills and their close relatives and was able to determine
that they generally (though not always) synchronize their nesting
cycle with the lunar cycle. The eggs tend to hatch as the bright
half of the lunar cycle is beginning.
And why not synchronize things this way? I speculate
that the first two weeks of the nestlings' lives are the most
precarious and the moonlight allows foraging by the parents through
the night.
I further speculate that during the second two weeks
the nestlings will have some reserves, allowing them to get through
the dark periods, and during the third two weeks they are becoming
independent and need all the help from moonlight they can get.
These were interesting results for me,
and the relationships with twilight and the moon were
distinct and obvious. Spending hundreds of hours with these birds,
however,
yielded other bits of information.
Whip-poor-wills are sometimes double-brooded.
One of my pairs began a second clutch before the
first brood (of which only one survived) was independent.
It was clear that the first nestling was primarily
the male's responsibility while the new clutch was the female's.
Both clutches synchronized with
successive
lunar
cycles.
Whip-poor-wills become torpid in cold weather. We
searched in vain one cold May for a radio-tagged bird.
Eventually,
an assistant of mine stepped on its tail! We were
able to pick it up. Except for a groggy head-rolling,
the
bird seemed dead, and I lamented-prematurely-the
loss of one of the study animals.
However, that evening it was flying around,
singing loudly, defending its territory, none the
worse for its earlier condition.
At the end of the season, I was able to remove most
of the radio tags.
Although many people object to causing stress to
birds by such studies, I can confirm that of the five pairs I
studied, four pairs successfully raised young despite the fact the
parents were tagged. Five of my seven nests were successful, a
remarkably high ratio when compared with most studies of other birds.
Identifying birds and listing is fun.
Finding rare species is exciting. However, there is a
deeper satisfaction in patiently studying and getting to know a
particular
species
or
group of individuals.
Reference
Mills,
A.
1986. The influence of moonshine on the behaviour of
goatsuckers
(Caprimulgidae).
Auk
103:
370-378.
Alex Mills lives in
Barrie,
where he is
a keen
member of
Barrie
's Brereton
Field Naturalists Club.
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