Biology Reference
In-Depth Information
gration? These exceptional dawn choruses are also most common in the temperate zone,
where birds have a compressed breeding season lasting only a few short weeks.
Whatever the reasons for it, the dawn chorus is one of the truly spectacular yet every-
dayoccurrencesthatmostofustakeforgranted.Ifthebirdswakeyouupinthemorning,
consider stepping outside to listen, or even getting up before dawn and going to a natural
area near you, where you'll experience an even more unforgettable show.
More than Just Melody
Q I've heard mockingbirds singing songs that I know belong to other birds — what's
going on? Why do they imitate so many other sounds?
A
Although some birds learn their species' song during their first year of life, others, in-
cluding mockingbirds, continue adding to their repertoire as they grow older. Northern
Mockingbirds can learn as many as 200 songs and often mimic sounds in their environ-
ment including other birds, car alarms, and creaky gates. One theory is that if a female
prefers males who sing more songs, a male can top his rivals by quickly adding to his
collection some of the sounds around him. Possessing a diverse assortment of songs may
indicate he is an older male with proven longevity and survival skills — good traits to
pass on to offspring. An older male may also be more experienced in raising young or
may have access to better resources.
According to one study on the Edwards Plateau in Texas, mockingbirds with the
largest selection of songs have the best territories, laden with foods such as insects,
wild grapes, and persimmons. One 2009 study found that mockingbird species in areas
with unpredictable or harsh climates include more imitations in their songs than those
in milder climates. In harsher areas, it may be more critical for females to be extremely
choosy about which mates they accept.
