Bulletin - United States National Museum - si-pddr - Smithsonian ...

BIEDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 21
position was that birds on the latter course had come south by the
interior route perhaps to reach the coast near Bahia Blanca, and
were now turning to seek their winter homes.
With regard to the migratory movement of native birds, particularly
in Argentina, many instances are noted in the writings of Dab-
bene, Gibson, Hudson, and others, while Peters has given an account
of the arrival of a number of species in northern Patagonia. In
general, such migratory movements are as readily evident to the
field observer as in northern regions. Large numbers of ducks of
various kinds, seed snipe, small ground-haunting flycatchers {Les-
sonia r. rufa), a subspecies of house wren, and other birds appear in
the Province of Buenos Aires from more southern regions at the
commencement of winter, and wholly or in part withdraw again as
summer approaches. Other species, as Thermochalcis Jongirostris.
are regular birds of passage from Brazil to Patagonia. The migra-
tory flights of the fork-tailed flycatcher are as evident as those of the
northern kingbird {Tyrannus tyrannus), for at the end of January
these birds gather in flocks and begin a northward movement that
carries all to Brazil during the following month. The jacana, the
sulphur-bellied flycatcher {Myiodynastes solitarius)^ two species
of martins {Progns elegans and Phaeoprogrie t. tapera), and a small
swallow {Iridoprocne alhiventris) are summer visitants near Buenos
Aires that retire at the approach of cold, as do the greater part of
other small species, some of whose individuals are hardy enough
to remain.
Even in the Paraguayan Chaco, in the edge of the Tropics, the
spring migration was easily evident, as with the approach of warmer
days in September Podager nacunda passed in small numbers to
the south (making as regular a flight as the North American nighthawk),
a kingbird {Tyrannus tn. melancholicus) ^ and another fly-
catcher {Myiodynastes solitarius) appeared, and a little goatsucker
{Setopagis parvulits), hitherto absent, began its tremulous calls
at evening.
The low woodland of the level reaches of the Chaco, with its
dense jungle impervious to cold winds, and its tangled openings,
where the sun may be warm even on sharp frosty mornings, harbors
many winter visitants from the more open country to the south, or
from the mountain slopes to the west. Here many small flycatchers,
warblers, and other insect-eating birds rest in comfort and security,
remaining quiet during brief spells of cold and becoming active when
the sun appears. The woodlands to the westward that cover the
low hills in northern Tucuman are also attractive at this season, and
at times small birds are so abundant there that they fairly swarm.
Altitudinal migrations were easily evident in the Andean foothills
in Mendoza, as flycatchers and others came working down