Biology Reference
In-Depth Information
ory, many headed to Scania, in the southernmost tip of the Scandinavian Peninsula, and
to the East German Baltic coast.
Q What do birds do while they are “on vacation” in the tropics? Do they just loaf
around and eat?
A
Many birds, males and females alike, use as much energy defending a winter territory
as they do a breeding territory. There are great advantages to knowing every inch of a
familiar plot of land for finding food, hiding from predators, and having safe roosting
places. Therearemanydangersinthetropics,andbirdsmustcompete withatremendous
number of other birds for resources.
Some birds, such as Eastern Kingbirds, that specialize on a high-protein insect diet in
the north while producing eggs and feeding young may switch to a fruit diet in winter.
Fruit-eaters such as these may be highly territorial in summer, but on their wintering
grounds peaceably associate in flocks, wandering widely in search of new food supplies.
Whether they defend a winter territory or associate in a flock, wintering birds must re-
cover from their arduous autumn migration and get back in condition to migrate north all
over again when the time comes.
Q Do any Central or South American birds spend their winter up here in North
America?
A
A few individual southern birds wander north after their own breeding season, but
those are anomalous cases. About 220 to 240
austral migrants
(birds that breed in the
SouthernHemisphereandmigratenorthfortheirwinter)breedintemperateSouthAmer-
ica and winter toward the Amazon basin. Most austral migrants do not winter as far as
the tropics — only 32 species reach Amazonia and 14 more winter north of the Amazon
basin. This, by the way, compares with about 420 species that breed in temperate North
America and winter in the Neotropics.
Q Robins are supposed to be harbingers of spring but I see them all winter in Min-
nesota! How is that possible?
A
Robins switch their diets from primarily worms and insects in spring and summer to
primarily fruits in fall and winter. They can survive as far north as they can find a con-
sistent supplyoffood.Robinsareinteresting migrants —ratherthananorth-southroute,
