|
Diet and
Food Consumption
Bald eagles
feed on a variety of prey items including fish (mostly
shallow-water fish like gizzard shad, cisco, suckers and small
northern pike), waterfowl, seabirds and small mammals like
rabbits. Eagles will also take advantage of road-kill and carrion
(dead animals). Scavenging allows eagles to conserve energy in the
winter by providing them with food that has taken little effort
(fewer calories) to obtain. Scavenging is the most popular feeding
strategy. Juveniles will depend on carrion as a primary source of
food until they become more proficient at hunting.
Adults and chicks will eat the same prey, but adults will tear the
prey into bit-sized pieces for their chicks using their sharp
beaks. Older nestlings can tear apart whole prey on their own.
Juveniles have significantly larger wing and tail surfaces. This
allows them to be more efficient at soaring and in turn more
effective at locating carrion.
Another way that an eagle will obtain food is by stealing it from
another bird like another eagle or osprey. Many times one eagle
will harass another until it is forced to drop the prey in order
to defend itself from the others’ talons. The pursuing eagle
will then dive at top speed after the prey that was dropped. It is
sometimes able to catch the dropped prey in mid air. Otherwise the
eagle will retrieve it from the water or the ground where it has
fallen. This chase may look as thought it is by chance, but it
isn’t, the dominant will steal from the subordinate and the
larger bird will steal from the smaller. Stealing is the second
most popular feeding strategy.
Eagles take much of their food from the surface of the water. Many
times eagles will perch on the windward side of the islands or
peninsulas allowing the prevailing winds and waves to wash up the
dead or dying fish. People have reported seeing eagles take
waterfowl right out of the sky, but usually they will harass them
until they tire and need to land. This makes the much easier for
the eagle to catch.
There are times
that an eagle will follow a diving duck, with talons outstretched,
into the water becoming completely submerged. Some people have
seen eagles dig up burrows of petrels, anklets and puffins in
order to capture the birds. There have also been some reports that
an eagle will even crush and devour the contents of other birds’
eggs.
Actually
catching their prey is the least popular feeding strategy. While
to some this sounds like laziness, it is actually a highly
developed method of energy conservation. Using the most energy
efficient foraging method can mean a longer, less stressful life
for an eagle.
Prey Requirements
In order to
maintain body weight and have energy to function, an eagle must
find food sources with sufficient calories.
Compared to the
red meat of mammals (deer, raccoon, skunk and possum) fish are
poor food sources, however fish are more likely to be available.
If an eagle eats only fish it would need to consume from 6% –
11% of its body weight a day (anywhere from 1 to 1.5 pounds of
fish. If it fed on a higher quality of food, like carrion or small
mammals, it would need only about 6% of its body weight each day.
Weather (air
temperature) and the amount of energy expended in locating food
also affects how much food a bird needs. Eagles can go without
food for several days.
Feeding Behaviors
Eagles watch
each other for clues about food. Young birds follow the older
birds from winter roosts to hunting or scavenging locations,
thereby learning the skills necessary to survive.
Many eagles
will very quickly surround carrion discovered by one eagle. Eagles
use each other to spot prey, or carrion sources. This is where
their outstanding vision comes into play. An eagle can spot
another eagle soaring from up to two miles away and is able to
locate prey in this way. Other times an eagle may take advantage
of other birds like crows or ravens to locate food.
About a half-hour before sunrise eagles will leave their night
roosts and choose hunting perches in their feeding areas. For
about an hour after sunrise they fish and feed heavily. Once
they’ve eaten their fill they will spend much of the rest of the
day perched in trees intent on conserving energy. They may take
flight again if assured of getting food as a reward for their
energy expended. |
Home
Panoramic
View
