Woodland - Winter 2019 - 15

MICHAEL WOODRUFF/SHUTTERSTOCK.COM

occur, but in most cases observers
can only speculate on the cause
because they lack information
on the nesting histories of the
species involved," said Julian Avery,
assistant research professor of
wildlife ecology and conservation
in the College of Agricultural
Sciences. "But in this case, we had
much more information."
For the industrial noise pollution
study, researchers placed 80 nest
boxes along gravel roads and
fields in pairs, with paired boxes
slightly more than three feet apart
and about 100 yards between
pairs. They paired the nest boxes
to maximize settlement by Eastern
bluebirds and tree swallows, which
often are willing to nest in close
proximity.
The researchers subjected
20 of the paired boxes to noise
that played 24 hours a day from
large speakers placed just behind
the nest boxes. The sound
was recordings of a shale-gas
compressor that looped to create
continuous noise, loud enough
to simulate an active compressor
station.
As part of the study, researchers
recorded behavioral observations
using cameras in the nest boxes.
They observed each box once
during incubation, once when the
nestlings were young and a third
time when nestlings were older.
"We crossed our fingers and
hoped birds would move into the
site to occupy those boxes, and
they did in large numbers, so we
had a nice experimental treatment
between birds nesting in quiet
boxes and birds nesting in very

noisy boxes," Avery said. "We'll
be reporting soon on how the
industrial noise pollution affected
the birds, but first this interspecific
feeding component is fascinating."
Lead researcher Danielle
Williams, who received a master's
degree in wildlife and fisheries
science in 2018, recorded the
number of feeding events at the
boxes by each parent in three-hour
observations and analyzed the
footage. That's how she learned
about the male bluebird repeatedly
feeding tree swallow nestlings in
Box 34B.
This nest contained four 10-dayold tree swallow nestlings. The
second box in the pair, 34A,
contained four Eastern bluebird
eggs. The bluebird pair occupying
box 34A had fledged young from
box 34B more than a month before.
The tree swallows then took over
the box and laid their eggs, forcing
the bluebirds to move to box 34A
for their second brood.
"We inserted a camera into
nest box 34B for an older nestling
observation, and during the threehour observation period, the male
Eastern bluebird nesting in box 34A
was shown providing food to the
tree swallow nestlings 29 times,"
Williams said. "When I looked at
the video, I realized that there was
a bluebird male in there caring for
the young."
The researchers, who noted
that many songbirds do not
recognize the begging calls or the
appearance of their own young,
believe the male bluebird, because
he had nested in this box earlier
in the season, was confused. He

made a "place-based decision" to
care for the young tree swallows.
"In this case, we think the male -
since he was primed to raise
nestlings and respond to begging
behavior - was duped because he
was hearing all of these begging
calls and remembered this box,"
Avery said. "It's especially cool
because he is going in and out of
the box as the female tree swallow
does as well."
The bluebird even perched
beside the female tree swallow on
the box lid, Avery added.
"You'd think at that point the
male bluebird would realize the gig
was up," he said. "He is engaged
in very detailed behavior, even
picking up and removing the tree
swallow chicks' waste. He doesn't
seem to have a clue."
The findings, recently
published in the Wilson Journal
of Ornithology, are important in
helping us understand animal
behavior, according to Avery.
"With all the other random
observations out there of
interspecific feeding behavior,
observers never had any indication
what was driving it," he said. "With
this we do, and we know to what
degree the urge to care for young
overrides other considerations."
Margaret Brittingham, professor
of wildlife resources and extension
wildlife specialist, also was involved
in this research.
Penn State's Schreyer Institute for
Teaching Excellence, the Association
of Field Ornithologists and the U.S.
Department of Agriculture's National
Institute of Food and Agriculture
funded this study.
A

Winter 2019 * WOODLAND 15



Woodland - Winter 2019

Table of Contents for the Digital Edition of Woodland - Winter 2019

OVERSTORY
FORESTS AND FAMILIES
FOREST INTERACTIONS Seedlings
2019 Outstanding Tree Farmers of the Year
Giving Back for the Forests of Tomorrow
Policies And Partnerships Go Hand In Hand For Strong Forests
TOOLS AND RESOURCES
Woodland - Winter 2019 - Intro
Woodland - Winter 2019 - cover1
Woodland - Winter 2019 - cover2
Woodland - Winter 2019 - 3
Woodland - Winter 2019 - OVERSTORY
Woodland - Winter 2019 - 5
Woodland - Winter 2019 - FORESTS AND FAMILIES
Woodland - Winter 2019 - 7
Woodland - Winter 2019 - 8
Woodland - Winter 2019 - 9
Woodland - Winter 2019 - FOREST INTERACTIONS Seedlings
Woodland - Winter 2019 - 11
Woodland - Winter 2019 - 12
Woodland - Winter 2019 - 13
Woodland - Winter 2019 - 14
Woodland - Winter 2019 - 15
Woodland - Winter 2019 - 16
Woodland - Winter 2019 - 17
Woodland - Winter 2019 - 18
Woodland - Winter 2019 - 19
Woodland - Winter 2019 - 2019 Outstanding Tree Farmers of the Year
Woodland - Winter 2019 - 21
Woodland - Winter 2019 - 22
Woodland - Winter 2019 - 23
Woodland - Winter 2019 - 24
Woodland - Winter 2019 - 25
Woodland - Winter 2019 - Giving Back for the Forests of Tomorrow
Woodland - Winter 2019 - 27
Woodland - Winter 2019 - 28
Woodland - Winter 2019 - 29
Woodland - Winter 2019 - 30
Woodland - Winter 2019 - Policies And Partnerships Go Hand In Hand For Strong Forests
Woodland - Winter 2019 - 32
Woodland - Winter 2019 - 33
Woodland - Winter 2019 - 34
Woodland - Winter 2019 - 35
Woodland - Winter 2019 - TOOLS AND RESOURCES
Woodland - Winter 2019 - 37
Woodland - Winter 2019 - 38
Woodland - Winter 2019 - cover3
Woodland - Winter 2019 - cover4
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