(WHITE-THROATED SPINE-TAIL.)
+Synallaxis albescens+, _Scl. et Salv. Nomencl._ p. 63; _Scl. P. Z.
S._ 1874, p. 9; _Durnford, Ibis_, 1877, p. 180 (Buenos Ayres);
_White, P. Z. S._ 1882, p. 611 (Misiones); _Barrows, Bull. Nutt.
Orn. Cl._ viii. p. 207 (Entrerios).
_Description._--Above, forehead grey, crown pale chestnut; sides of
head and neck, back, and tail pale earthy brown; upper wing-coverts
pale chestnut, wing-feathers olive-brown; beneath white, faintly
washed with earthy brown; under wing-coverts fulvous: whole length
5·3 inches, wing 2·0, tail 2·2.
_Hab._ S. America, from Veragua to Buenos Ayres.
This species, although by no means abundant in Buenos Ayres, is met with
much more frequently than the _S. spixi_, which it closely resembles in
size, colour, habits, and language. It is, indeed, an unusual thing for
two species so closely allied to be found inhabiting the same district.
In both birds the colours are arranged in precisely the same way; but
the chestnut tint on _S. albescens_ is not nearly so deep, the browns
and greys are paler, and there is less black on the throat.
I am pretty sure that in Buenos Ayres it is migratory, and as soon as
it appears in spring it announces its arrival by its harsh, persistent,
two-syllabled note, wonderfully strong for so small a bird, and which it
repeats at intervals of two or three seconds for half an hour without
intermission. When close at hand it is quite as distressing as the
grinding noise of a Cicada. This painful noise is uttered while the bird
sits concealed amid the foliage of a tree, and is renewed at frequent
intervals, and continues every day until the Spine-tail finds a mate,
when all at once it becomes silent. The nest is placed in a low
thorn-bush, sometimes only two or three feet above the ground, and is an
oblong structure of sticks, twelve or fourteen inches in depth, with the
entrance near the top, and reached by a tubular passage made of slender
sticks, and six or seven inches long. From the top of the nest a crooked
passage leads to the cavity near the bottom; this is lined with a little
fine grass, and nine eggs are laid, pear-shaped and pale bluish white in
colour. I have found several nests with nine eggs, and therefore set
that down as the full number of the clutch, though I confess it seems
very surprising that this bird should lay so many. When the nest is
approached, the parent birds remain silent and concealed at some
distance. When the nest is touched or shaken, the young birds, if nearly
fledged, have the singular habit of running out and jumping to the
ground to conceal themselves in the grass.
I have no doubt that this species varies greatly in its habits in
different districts, and probably also in the number of eggs it lays.
Mr. Barrows, an excellent observer, says it lays three or four light
blue eggs. He met with it at Concepcion, in the northern part of the
Argentine Republic, and writes that it is "an abundant species in thorny
hedges or among the masses of dwarfed and spiny bushes, which cling to
each other so tenaciously amid the general desolation of the sandy
barrens." The nests which he describes vary also in some particulars
from those I have seen. "Entrance is gained by the bird," he says,
"through a long tube, which is built on to the nest at a point about
half way up the side. This tube is formed by the interlocking of thorny
twigs, and is supported by the branches and twigs about it. It may be
straight or curved; its diameter externally varies from two to four
inches, and its length from one to two feet. The passage-way itself
is but just large enough to admit the birds one at a time, and it has
always been a mystery to me how a bird the size of a Chipping-Sparrow
could find its way through one of these slender tubes, bristling with
thorns, and along which I found it difficult to pass a smooth slender
twig for more than five or six inches. Yet they not only pass in and out
easily, but so easily that I was never yet able to surprise one in the
nest, or to see the slightest disturbance of it by the bird's hurried
exit."
The bird has a very wide range in South America, and Mr. Salmon observed
its breeding-habits in Antioquia in Colombia. There also the bird varies
the form of its nest, making it as large as that of an English Magpie,
and roofing the top with a mass of large leaves to protect it from the
heavy rains. The eggs, he says, are very pale greenish blue, nearly
white; but he does not give the number.