Biology Reference
In-Depth Information
In some cases, mimicry may result from the song-learning process gone awry, such
as reports of a Vesper Sparrow and House Wrens singing songs of the Bewick's Wren,
and an Indigo Bunting and a Common Yellowthroat singing a Chestnut-sided Warbler
song. It seems that a fairly large number of these occasional mimics are unpaired, sug-
gesting that males who learn the wrong songs often fail to pass their genes to the next
generation. Selection against birds who learn the wrong songs may thus be very strong,
so “mistakes” are not perpetuated.
Q When I went on a birding trip to the tropics, our guide told us to listen to the
sounds of birds that he said were a male and a female wren duetting. Do our back-
yard birds duet too?
A
Interestingly, duets are far more common, complex, and coordinated among tropical
birdsthantheyareamongspeciesthatbreedinthetemperatezone.Forexample,afemale
Red-winged Blackbird may join in a duet by uttering a loud series of notes during the
last half of her mate's
oakalee
song. In contrast, some tropical wrens sing such highly
coordinated duets that unless the birds are far apart, it's hard for a listener to even realize
that more than one bird is singing. Other tropical duetting species include some parrots,
woodpeckers, antbirds, flycatchers, shrikes, and wrens.
Birdsthatareresidentinthetropicsaremuchmorelikelytomaintainlong,monogam-
ous bonds and to live year-round on their territory. This may provide more opportunity
for them to develop complex duetting, which may further strengthen their bond or aid in
joint defense of the territory.
Q I've often heard the Song Sparrows behind my house singing a beautiful melody,
but I was surprised when I heard one make a short little chirp that sounded nothing
like the songs. Was it a young bird that didn't know how to sing?
A
Not necessarily. You heard a contact call, a sound that the birds use to tell one another,
“Hey, I'm here.” Males, females, adults, and juvenile birds may all use this call year-
round. In contrast, it's typically only male Song Sparrows who sing the more complex
melodies. They only sing during the breeding season, to advertise their presence to fe-
males and to warn males to stay off their territory. (In rare cases, female Song Sparrows
sing, but their song is usually simpler than that of the males.)
Sparrows may also use a variety of other vocalizations to communicate with one an-
other.Forexample, SongSparrowsutter ahigh-pitched alarm note that ornithologists de-
scribeasa
tik
whenahawkfliesoverhead.Theyusealower-pitchedcalldescribedas
tch-
unk
when humans approach a nest or fledglings. Females make a harsh chattering sound
to their mates during nest building, and they utter a nasal trill after mating. Both males
