C3o—Lancaster Farming, Saturday, April 12,1980
Shift
in war against blackbirds
NEWARK, Del. - The
blackbird has a long record
as a troublemaker by far
mers. Even the Indians had
problems with this hungry
marauder.
In the prolonged war
between man and this
particular feathered beast,
man has often been the loser.
But a shift in battle tactics
today has increased the odds
in the fanner’s favor, says
Jack Lmehan, a biologist
with the U.S. Fish and
Wildlife Service stationed at
the University of Delaware’s
Agricultural Experiment
Station in Newark.
A specialist off blackbird
behavior as it relates to
damage on field corn, he is
quite familiar with the
problem.
There are two basic kinds
of bird predation on com
sprout pulling (seed eating)
and ear damage. Each af
fects the farmer differently.
With seed loss you often have
an opportunity to replant
at additional cost, of course.
But once the ripening ears
are damaged, the farmer
has lost at least a part of his
crop.
Over the years, any
number of farmers with land
near the marshes that flank
the Delaware River have
gone out of business because
of repeated blackbird
damage. Others have
managed to stay in operation
by changing the way they
farm
Lmehan says damage
avoidance methods are by
far the most realistic ap
proach in areas with heavy
blackbird pressure. Such
methods are much more
likely to be successful in
producing a harvestable
crop than an all-out effort at
bird control.
Seed eating or sprout
pulling, for instance, can be
avoided by improving
cultural practices. Fanners
are most apt to get bird
damage to newly planted
seed under the following
conditions; shallow planting,
rather loose soil, rain or
moisture at the time of
emergence, delayed ger
mination and delayed
sprouting due to poor ger
mination and cold soil.
Seed eating can also be
discouraged by use of a
repellent such as
methiocarb.
Unfortunately, some of the
best seed treatments can
reduce germination. So
make sure your com seed
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in tactics
has good viability. Other
wise especially if tne
ground is cold when you
plant you’re likely to
suffer some losses even after
treatment. The decision to
use a repellent should be
based on the anticipated
level of bird damage, as well
as the cost of seeding.
“If you won’t have a
chance to replant, you’d be
smart to treat,” says the
biologist.
There are also a number of
ways to reduce losses from
ear damage on ripening
com.
First, plant a variety
that’s resistant to damage. If
you farm where blackbirds
are likely to be a problem, it
pays to choose a hybrid with
a heavy husk and good tip
coverage.
Then grow your crop so
that this husk growth is
encouraged. This means
cutting down the plant
population and increasing
fertility to get bigger ears,
since these tend to be more
resistant to damage. Do this
in fields with a history of
bird damage
Tuning is also critical for
damage avoidance. Lmehan
says vulnerable fields should
be planted so that com goes
through the milk and dough
stages in mid-August. At this
time it’s least likely to be
attacked. Com which enters
these stages earlier or later
in the season is very
vulnerable.
For the most part,
resistant varieties tend to be
long-season hybrids.
Plantings should go in
around the first week of May
in Delaware.
For the past six years
Lmehan has been studying
field corn varieties to
determine their resistance to
bird damage from ear
feeding. So far he’s rated a
total of 265 commercial
hybrids grown in plots in
Delaware and southern New
Jersey.
Results range from nearly
zero to six percent injury
among the most resistant
varieties, to 40 or 50 times
that much among the most
susceptible.
Among those varieties
which performed best were:
Taylor Evans Silagemaster,
Agway 840 X, PAG SX39,
Gutwem 92, Todd M9O,
Agway 834 X, Midstates
747 A, McNair X 212, Mid
states 900, Midstates 869,
Taylor Evans E2OYA, Todd
MBB, Doebler 70X, Northrup
Call:
improves odds
King PX77, Hardy 600 X,
Pioneer 3369 A, Midstates
879, USS 1010, and Midstates
816.
Of course, bird resistance
is only one of many factors to
be considered in the selec
tion of a com hybrid. But it’s
one to think about if bird
damage is a problem on your
farm.
Besides altering cultural
practices and selecting
resistant hybrids, there are
other ways to protect a
maturing com crop. One of
these is through scare
devices. The most com
monly used are exploders
that work off carbide or
bottled gas. These are rather
expensive to use, require
considerable maintenance
and can damage the
operator’s hearmg if they go
off while he is up close
without ear protection.
Their effect also
diminishes with distance.
But in spite of these
drawbacks, they do
minimize damage.
“There are many, many
com crops in the Delaware
Valley which wouldn’t have
been worth harvesting at all
if it weren’t for such
devices,” says the biologist.
Another way to protect
your maturing «crop is
through chemical behavior
control, using a material
called Avitrol. This is ap
plied to cracked com and
then scattered by air as a
bait m ripening com.
Its effectiveness as a
repellent is based on the
social nature of blackbirds.
When one eats a piece of the
treated com his erratic
behavior and distress calls
tend to frighten away other
members of the flock.
Linehan was one of the
scientists involved in
research which led to ex
tending clearance of this
material for use on sweet
com a few years ago
He says m some cases
Avitrol has proven quite
effective, but it’s not
guaranteed to work. It’s also
toxic and should be con
sidered as a poison.
Directions for its use are
very specific and must be
followed to the letter, as it is
capable of killing other
wildlife.
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Incidentally, the biologist
says there used to be a lot of
sweet corn grown in
Delaware for processing.
Heavy bird damage is one
reason this crop.has gone
out. In fact, U.S. 13 used to
be the dividing line when
processors were awarding
contracts to sweet com
growers, because the closer
you get to the river, the
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greater the bird pressure.
Soybeans aren’t nearly as
vulnerable to bird predation
as sweet or field com, so to
avoid loss a number of
farmers have switched to
this crop in recent yfears.
This is one way around the
problem, but it does mean
the birds have deprived the
grower of one of his options
as a farmer. This loss of
options can cost dearly in a
year when com brings a
better return than beans
Lmehan said he feels that
bird pressure has remained
fairly constant in Delaware
over the years he’s been
here. But the amount of
damage is down primarily
because growers in the “bird
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belt” along the river have
switched to other crops.
Redwing blackbirds are
the main cause of damage to
maturing com in this region
Grackles (or “crow
blackbirds”) do the most
damage to seed. Cowbirds
tend to associate with the
other two species but
damage sorghum, not com.
Most people lump all three
under the category of
“blackbirds.”
Population estimates are
often based on the highest
number present in a single
day. The peak usually occurs
during either the fall or
spring migration. Nearly all
the East Coast blackbird
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