Pennsylvania Game News - May 2018 - 55

nest beside the first one, yanking
nesting materials from the first nest as
the youngsters watched and screamed
in hunger.
The male fed the nestlings while
the female built the second nest. But
sometimes when the nestlings begged,
the female would push construction
materials into their mouths, and they
promptly spat them out.
They nestlings jumped back and
forth between old and new nests, before
settling into the old nest for the night.
The following morning, at 9:30, they
all fledged at once - unusual behavior
for birds that typically fledge one at a
time.
While I kept a "hands off" approach
to the young at the nest I watched,
Audubon spent his time gaining the
trust of both parents and nestlings so
they tolerated the light silver thread
he fastened to the leg of each nestling
before it fledged.
It's regarded as the first time birds
were banded in North America, and the
following year it proved that phoebes
return to the same nesting site and even
the same nest.
"There again in the very same nest
two broods were raised...Several of
these birds which I caught on the nest
had the little banding ring on the leg..."
Audubon wrote.
He assumed many of the pairs he
observed, not only in the cave, but
on farm buildings and nearby mill,
remained faithful during one breeding
season and from year to year.
Recently, two studies found that most
pairs were both socially and genetically
monogamous within a breeding season.
In one case, in Indiana, only 15 of 87
MAY 2018	

families had extra-pair young in at least
one brood, most commonly the second
brood.
A follow-up study captured and
color-banded 198 males and 237
females that were studied for three
seasons, showing they were faithful to
their territories, nest sites, and mates
within and between years, with 85.5
percent of males and 92 percent of
females breeding with the same mate
during multiple attempts.
But mates were replaced following
their disappearance and probable deaths.
In a Kentucky study, researchers
hypothesized a male observed killing
all young in a nest did so because their
father had died or disappeared, and the
male was attempting to obtain their
mother as a mate so he could start his
own family.
A greater threat to breeding phoebes
has been repeated brood parasitism by
brown-headed cowbirds, which I've
occasionally observed in our nests over
the years.
A study in New York state concluded
that cowbirds prefer particular eastern
phoebe sites, even over generations of
birds.
Other threats to phoebe eggs and
nestlings are black rat snakes, raccoons,
coyotes, blue jays, American crows,
chipmunks and house wrens.
Overall, phoebes are incredibly
successful throughout their range,
including in Pennsylvania, where they
live everywhere except within the urban
cores of Philadelphia and Pittsburgh.
Although our songbird population
has dwindled since the 1970s, it
is comforting to know that eastern
phoebes continue to thrive and can
quickly adapt man-made structures for
their own purposes.
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Pennsylvania Game News - May 2018

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