Pennsylvania Game News - July 2019 - 51

all are the gourds that are so deep that the
martins can raise seven young in them
instead of what more typically is four in
bird-house compartments.
Nest-building in Pennsylvania begins
in early to mid-May and is mostly done
by the female, although the male may
collect green leaves and sometimes starts
nest-building by gathering a few twigs or
leaves. But once the female begins, the
male either accompanies her while she
gathers nesting material or sits near the
nest cavity and watches.
Each pair designs its own nest, so they
vary widely in shape. The depressed nest
bowl is filled up with green leaves that
often hide three to seven white eggs. In
Pennsylvania, returning martins reuse the
same nest cavities and fledge more young
than martins that use clean compartments.
The female has a brood patch and is
thought to be the incubator during the
15 to 18 days of incubation, but the male
often relieves her for long periods.
The altricial young hatch and are
brooded by the female until their eyes
open in 10 days. Both parents feed the
nestlings and, when they are 12 days old,
they cluster together near the entrance
hole to greet their parents. By the time
they are 17 to 21 days old, they have their
feathers and are exercising their wings
by stretching and flapping. Finally, they
fledge when they are 28 to 29 days old. In
northwestern Pennsylvania that is usually
mid-July.
Their parents continue to feed them for
several days, but the young begin catching
insects on their own and are fully independent seven to 10 days after they fledge.
Then they join other fledglings in roosts.
Under a program called Project Martin
Roost, the Erie-based Purple Martin
Conservation Association has discovered at least 350 pre-migratory roosts in
JULY 2019	

eastern North America and Canada, most
of which are so large they show up on
weather radar.
The association in late summer conducts sunset pontoon boat tours of the
20,000-martin roost at Presque Isle Bay,
which draws in birds from up to 250 miles
or more.
Typically the roosts are over large
bodies of water and given cover from
reed beds and brushy islands. But in urban
and suburban settings, martins roost in
large numbers in trees or on man-made
structures such as bridges and pipes. The
farther south these roosts are, the longer
the martins remain. Some are used from
eight to 12 weeks.
Stutchbury's geolocator studies show
that, once the Pennsylvania birds head
south, they fly almost nonstop until they
reach Central America, as soon as five
days later. They then rest before continuing to Brazil, more slowly than when they
head north in the spring.
Wet weather is the largest threat to
purple martins. If there is a long, cold,
rainy spell in June and July, most of the
year's progeny will perish of cold, drown
in their nests, or die of starvation since
martins don't fly in wet weather. European
starlings and house sparrows also might
take over martin nests, so martins depend
on their human landlords to remove the
non-native invaders.
Owls and snakes also are a threat and
deeper cavities make nests harder for owls
and other avian predators to reach into.
Snake guards installed on bird house poles
can keep them away.
With enough folks willing to be
purple martin landlords, the eastern
population of this beautiful bird should
grow and thrive.
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Pennsylvania Game News - July 2019

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