Biology Reference
In-Depth Information
Building the Best Nest
Q If robins make a nest in a bush close to the house one season, what are the chances
they will go back to the same place the next season to build their nest?
A
Ifthefemalesurvivesthewinter,andifshesuccessfullyrearedyoungthefirstyear,the
chancesareexcellent thatshewillreturntothesameplacethenextyear.Ifthenestfailed
for any reason, she will usually find a new place to build.
Q Do all birds sleep in nests?
A
No.Nestsaren'tdesignedtoserveasbedsforadultbirds.They'rereallyjustincubators
for eggs and hatchlings, and cribs for nestlings. Chicks of many birds, including ducks,
geese, and relatives of chickens such as grouse, leave their nest within a few hours of
hatching, never to return. Others remain in their nest until they can hop or fly.
Woodpeckers and other birds that nest in cavities often sleep in cavities even when
they're not nesting. Cavities protect birds from excessive cold and heat and, even more
important, from rain and snow and wind. But cavities aren't absolutely safe. Raccoons,
cats, and some other predators can reach into cavities to pull out sleeping birds, which
havenootherwayout.Andcavitiescanfosterparasites.Somebirdsroostincavitiesonly
on very cold nights; otherwise, they roost on branches. As soon as young woodpeckers
leave the nest, they move into abandoned cavities or excavate new ones for sleeping, and
switch to new cavities fairly often.
Thisiswhyit'ssoimportantforbirdstohavebothgoodnestsitesandgoodroostsites
in their habitats.
Q One day I looked out on my porch and a little bird was plucking fur from my
golden retriever! Why was it harassing my dog?
A
The bird wasn't trying to bother your dog; it was just taking advantage of a convenient
source of fur to gather soft insulation for its nest. Many birds, including Chipping Spar-
rows and Tufted Titmice, pluck fur from dead and sleeping animals. They also pluck tail
hairs from horses. Once I saw a Tufted Titmouse pulling hairs from the tail of a raccoon.
Thetailwasstickingoutofabigcavity,andtheraccoonwasapparentlysleepinginside.It
hardly moved at all as the titmouse collected hairs; suddenly it rolled over, its tail slowly
twisting around as the titmouse clung to it, finally flying off with a beakful of hairs.
The largest documented individual nest is that of a Bald Eagle in Florida; it was 20 feet
(6 m) deep, almost 10 feet (3 m) wide, and weighed almost 3 tons. The largest nest on
