Biology Reference
In-Depth Information
Birdscandistinguishtheindividualnotesofcomplex,rapidsongsmuchmoreeasilythan
wecan—tosaynothingofbeingabletoproducethosesongsinthefirstplace.AWinter
Wren in western North America sings an average of 36 notes per second! We can only
resolve those individual notes by playing back a recording of the song at slow speed.
Amongbirds,theOilbird—anocturnalspeciesofTrinidadandnorthernSouthAmer-
ica — and cave swiftlets of Southeast Asia are known to use echolocation. These birds
produce audible clicks that bounce off the cave walls and other impediments, such as
stalactites andstalagmites, allowingthebirdstosafelynegotiate theirtreacheroushomes.
But neither the swiftlets nor the Oilbird can produce ultrasound notes, so their sonar is at
best only one-tenth as functional as that of bats — Oilbirds can detect items only larger
than 20 millimeters in diameter and will collide with anything smaller.
The Nostrils Know
Q Can birds smell?
A People once believed that, with very few exceptions, birds couldn't smell at all. They
don'thaveaspecializednosebutsimplynostrils,necessaryforbreathingandusuallyloc-
ated near the base of their upper beak. But some species, including several ground birds
and also some North American vultures and marine species called “tubenoses,” do have
fairly large olfaction (smell) centers in their brains.
Many “tubenose” seabirds, especially petrels, shearwaters, and fulmars, locate their
oceanic food by smell. Petrels are attracted specifically to the smell of dimethyl sulfide,
an aromatic substance released by microscopic algae when tiny drifting invertebrate an-
imals called zooplankton are feeding on them. The petrels don't eat the algae; they're
afterthezooplankton.Thiszooplanktonisn'teasilyseen,andpetrelsfeedbynightaswell
as by day, so their sense of smell is very useful, and very keen.
Tiny Wilson's Storm-Petrels, smaller than American Robins, can detect slicks of di-
methyl sulfide from great distances. Their albatross relatives also have a good sense of
smell but are not attracted to dimethyl sulfide, probably because these larger birds feed
on fish and squids rather than plankton.
Recent studies have shown that even some songbirds, with relatively tiny olfaction
centers in their brains, can smell. For example, Cedar Waxwings, which eat berries that
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