Nest Watcher Program Saves Eaglets From Ticks
Biologists seeking answer to mysterious failure of productive bald eagle nest demonstrates the narrow path back from extinction
This Arizona bald eagle makes its home at Green Valley Park in Payson.
Photo by Andy Towle.
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#After
three consecutive years of failing to fledge its young bald eagles, an
important Arizona nest site is back to adding to the growth of the
state’s bald eagle population with two nestlings surviving to fledge on
their own.
#The
nest became a challenge for Arizona Game and Fish Department bald eagle
biologists when it began to fail at producing young eagles that made it
to fledging age after many years of consecutive success.
#“Returning
this once productive bald eagle nest to its former successful status
has been a priority for Game and Fish and its partners, but it required
some perseverance and innovative approaches that had never been tried in
Arizona,” says Kenneth Jacobson, bald eagle management coordinator for
the Arizona Game and Fish Department.
#The
Centers for Biological Diversity, Arizona Audubon and several Indian
tribes have been battling the U.S. Fish and Wildlife Service in court
for several years to reverse the federal government’s decision to delist
the Arizona population of bald eagles, in part to ensure funding
remains available for the innovative and highly effective Game and Fish
Nest Watch Program, which the department has promised to maintain even
if the Arizona eagles remain delisted.
#Other
state and federal laws protect both bald and golden eagles, but a
federal endangered species listing also protects federally owned
critical habitat for an endangered species. The population of nesting
Arizona eagles have been growing steadily, with several breeding pairs
established in Rim Country. The Arizona nesting birds don’t normally
breed with the much larger number of eagles that migrate through the
area and most of the new breeding territories have been established by
birds successfully reared in the state.
#That
makes the Game and Fish Nest Watch Program crucial, since it prevents
people from disturbing nesting eagles and has increased successful
reproduction by an estimated 20 percent.
#The
mysterious case of the seeming failure of one of the most successful
nest sites provided a strong illustration of the value of the Nest Watch
Program.
#The
“Orme” bald eagle breeding area was discovered by biologists in 1987.
From 2001 to 2008, the bald eagle pair that used the breeding area
successfully fledged 15 young — a feat accomplished by only two other
breeding areas in the state during the same period.
#In
2009, biologists were alerted to a problem when two of the nestlings
jumped from the nest and ended up on the ground. Nestwatchers assigned
to monitor the nest as part of the Bald Eagle Nest Watch Program noticed
the birds on the ground, and Game and Fish biologists intervened. An
examination showed the nestlings were covered in ticks that were slowly
killing them.
#During
the identification banding of the nestlings the following year,
biologists found the source of the ticks in one of the main support
branches for the nest. They treated the three nestlings with a bird-safe
insecticide in hopes of keeping the nestlings tick free until fledging.
Unfortunately, treating the nestlings proved unsuccessful, so
biologists attempted to spray the source of the ticks directly with
insecticide and also sealed the infested area with hardening foam.
#During
routine banding of the young eagles in 2011, the nestlings were
determined to be in good health, but it became apparent that neither
approach worked when the nestlings again were found to have tick
infestations several weeks later.
#Game
and Fish sought permits from the U.S. Fish and Wildlife Service and
took extraordinary measures: they carefully removed the tick-infested
nest after the nesting season, transported it offsite to be burned and
began to build two manmade nests away from the old nest tree.
#The Game and Fish Nest Watch Program has increased#successful reproduction by an estimated#20 percent.
#Sticks,
leaves and other natural debris from the desert floor were raised to
the tree top bucket-by-bucket to create “starter nests.” Bald eagle
nests average 3 feet wide by 5 feet long and can weigh up to 2,000
pounds. The adults add to the nest each year, making some of Arizona’s
larger nests up to 15 feet tall and more than 7 feet wide.
#The
male and female eagles used one of the manmade nests this year and
fledged the first two young to survive since 2008 when three young
fledged. In total, eight bald eagle nestlings died as a result of tick
infestation. One nestling was successfully rehabilitated in 2011 and
fostered into a nest in another breeding area.
#Arizona
expects the bald eagle breeding season to conclude in the coming weeks
when the last of the bald eagle nestlings in the northern parts of the
state fledge.
#Fledging, a nestling’s first flight, is considered a significant milestone for a young bird.
#Bald
eagle conservation in Arizona is a partnership effort of the Southwest
Bald Eagle Management Committee — a group of 25 government agencies,
private organizations and Native American tribes
