 January 29, 2018
Courtship behaviors
We have exciting updates on the new EagleCam. If you’ve checked in lately you’ve noticed a
bit of housekeeping activity as the eagles organize their nest, adding sticks
and arranging them as part of their breeding ritual. Nest building occurs prior
to mating, usually beginning one to three months beforehand. Photographers in
the area have captured some dramatic courtship displays, including some
entertaining and breathtaking swoops, cartwheels and stick exchanges in
mid-air. Eagles do not mate in the air, contrary to popular belief, but we
caught a rare sight at the nest last week.
Check our Facebook page
for video of the pair mating in the nest! They will mate several times a day,
on nearby branches or in the nest. This
means that egg laying could begin in as little as 10 days.
A coveted nest
This weekend, and over the past few weeks, there have been a
variety of bald eagle visitors to the nest, and many people have expressed
concerns that the resident male has vanished.
We believe the male is fiercely defending his territory, keeping him too
busy to visit the nest itself. He has
been seen in the area, and we also believe he is still the mate. The visitors
have ranged in age from one-year-old
juveniles to adults, attempting to claim the nest, the female or both. The resident female is fiercely defending her
nest, and she makes it very clear that her male is the only male she will
tolerate.
Night visitors
The infrared imaging feature on the new camera has proven to
be very informative. White-footed mice
and raccoons are regular nighttime visitors.
Our scientists believe the mice also use the eagles’ nest for their
nests! They feed on the “nestovers” from
the eagles and use the feathers and fur for making their little homes within
the large eagle nest. The raccoons also have been cleaning up the leftover
food, but they’ve been warned by the eagles that their visits will soon need to
end.
Poor quality streaming from the webcam has been frustrating
for viewers and cam operators as well.
We are working hard on these issues and have ruled out a number of
factors. The camera itself is running fine. We have no doubt that the
pixilation is happening somewhere else, but we can’t pinpoint it yet. The
microphone placed in the nest is not working. It’s not part of, nor attached
to, the camera. The mic will be
replaced, but not until the chicks are banded.
Xcel Energy generously provides the bucket truck to get us to the nest,
and we reserve these favors for necessity.
They have one truck for this region that reaches high enough for camera access,
and demand for this truck is high. We
ask that you remain patient while we work out the bugs of this brand-new
system.
Many birds and other animals have a variety of physical and
behavioral adaptations and strategies that allow them to survive even the
coldest weather. Here’s a look at ways these amazing birds survive and keep us
entertained throughout the long winter months.
Birds have a higher metabolism rate and thus, a higher body
temperature than humans, making it a challenge to maintain this body heat in
the winter. Many birds will spend the fall taking advantage of abundant food
sources to fatten up for winter -- something we humans try to avoid.
Feathers are excellent insulators and many grow extra
feathers during a fall molt, adding about 20 percent to their weight in winter.
Their feet are covered with specialized scales that minimize heat loss and they
can constrict the blood flow to their legs and feet so blood flows only to
their major organs. This means less energy is required to circulate blood and
less warmth is lost.
Yes, birds do shiver, especially in extreme conditions.
Shivering is a short-term strategy that raises their metabolic rate so they can
generate more body heat. Shutting the heat down is also an important strategy.
Birds can turn their legs into heat exchange stations, a term called “countercurrent
heat exchange.” Because the veins and arteries in their feet and legs are
located near each other, the warm blood leaving their body is cooled before it
reaches the extremity (like a foot). Similarly, cool blood is warmed before
entering the body. By cooling the blood before it reaches the foot, they do not
lose as much heat (less energy loss). By warming the blood before it enters the
body, they are less likely to get chilled by the cold blood.
Behaviorally, birds use a variety of techniques to conserve
body heat.
- Fluffing out their feathers to create pockets of
air for additional insulation.
- Tucking their beaks into their feathery
shoulders to breathe in the warm air of their body.
- Crouching to cover both legs with their wings
feathers to shield them from the wind and cold.
- Turning their backs to the sun to take advantage
of solar heating on a sunny day.
- Roosting together in shrubs or empty bird houses
to conserve much needed heat.
Many birds will go into “torpor” to conserve energy. When an
animal is in a state of torpor, its body temperature is lowered and its heart, metabolic
and respiration rates are slowed to conserve energy and calorie output. It’s a
short-term strategy (a few hours or overnight) for surviving frigid
temperatures and severe storms.
But how can a bird successfully hatch its eggs in the dead
of winter?
A few birds, such as the bald eagle and great horned owl,
rely heavily on a brood patch, a bare spot on the belly that facilitates heat
transfer to the egg during incubation. Interestingly, both male and female bald
eagles develop a brood patch and share in the incubation duties. This is not
true of the great horned owl.
EagleCam viewers can rest assured that the bald eagles are
well equipped to raise their young in the frigid Minnesota winters. Anyone can
help other birds and nongame wildlife stay warm in winter by donating to the Nongame Wildlife
Program tax checkoff. Just look for the “loon line” on Minnesota income tax
and state property tax forms and give a gift to help continue efforts to
provide quality habitat for all endangered, threatened and nongame species. It
may just help warm your winter!
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