North American– Neotropical Long-
Distance Migrant BirdsVarious species of orioles, tanagers, flycatchers,
grosbeaks, thrushes, buntings, and wood warblers (plate
15- 158), along with numerous other birds, nest in North
America, migrating north in spring and returning to
subtropical and tropical habitats after breeding season
concludes. While the breeding ecology of most of
these species has been well understood, their wintering
ecology and migratory stopover sites have only recently
been investigated, with fascinating results.
During autumn, 338 species (including shorebirds,
raptors, and numerous passerines), or about 52% of all
North American migrant bird species, fly to wintering
areas somewhere within Central or South America, as
far south as southern Chile and Argentina. This influx
may total somewhere between 5 and 10 billion birds,
but no one really knows with any certainty. The majority
of long- distance migrant passerines winter in Central
America, but many also winter in South America and
the Caribbean Islands, especially the Greater Antilles.
The density of North American migrants is high in the
Neotropics from November through March. Not only
are there innumerable birds— yearlings in addition to
adults— but the actual land area of Central America,
where many migrant species winter, is smaller, by
about a factor of eight, than available nesting area in
North America. Migrants ranging from Swainson’s
Hawks to Least Flycatchers (Empidonax minimus) are
packed into tropical America for the winter months.
Many North American migrants are from families
that evolved in the Neotropics. Tyrant flycatchers,
hummingbirds, tanagers, orioles, and wood warblers
all originated in the Neotropics, though their
speciation patterns may have been much affected
by their breeding ranges in North America. Long-
distance migrant species represent the relatively few
that ventured northward into the temperate zone,
extending their ranges, perhaps because the northern
summer presents an abundance of protein- rich insect
resources for the rearing of young, longer days in
which to feed, fewer predators, and the availability of
abundant nesting sites. Evidence suggests that during
the Pleistocene glaciation, speciation events occurred
in the northern breeding areas that added to the
diversity of long- distance migrant birds.
Neotropical migrant land bird species, when on their
tropical wintering grounds, use virtually all availablePlate 15- 158. The Bay- breasted Warbler (Setophaga castanea)
breeds in the boreal forests of North America and winters
in the humid forests of Colombia and western Venezuela,
occasionally to Peru and Brazil. This bird, which flies thousands
of miles annually, weighs a mere 12.5 g (about 0.44 oz)— and
thus you could mail two of them anywhere in the United
States for the price of a first- class postage stamp. The bird in
the photo is a male. Photo by John Kricher.Plate 15- 159. Kentucky Warblers typically winter within
tropical forests throughout Central America and into northern
South America. Photo by John Kricher.Plate 15- 160. Male Black- and- white Warbler in a typical
feeding posture along a limb, searching for arthropod food.
Photo by John Kricher.chapter 15 neotropical birds: the bustling crowd 315