_Tachornis phœnicobia._—+Mihi.+
[13] +Tachornis.+ _Generic Character._—Bill very short, depressed,
gape very wide, the sides suddenly compressed at the tip, which
is curved; the margins inflected: nostrils, large, longitudinal,
placed in a membranous groove, the margins destitute of feathers.
Wings very long and narrow; first quill tapered to a point: second
longest. Tail slightly forked, a little emarginated. Tarsi rather
longer than middle toe, feathered. Toes all directed forwards,
compressed, short, thick, and strong, with compressed claws.
Sternum immarginate, but with three foramina, one through the
ridge, and one on each side.
Length 4²⁄₁₀ inches, expanse 9⁴⁄₁₀, flexure 4, reach of wings
beyond the tail ⁹⁄₁₀, tail, outer feathers 1⁷⁄₁₀, uropygials 1³⁄₁₀,
rictus ⁵⁄₁₀, beak ³⁄₂₀, tarsus ¹⁄₄, middle toe rather less than ¹⁄₄.
Irides dark hazel; beak black; feet purplish flesh-colour; claws
horn-colour; inside of mouth, flesh-colour, tinged in parts with
bluish. Head smoke brown, paling on the sides; back, wings,
tail-coverts, and tail, sooty-black, unglossed, or with slight
greenish reflections on the tail. Across the rump a broad band of
pure white, the black descending into it from the back, in form of
a point; sometimes dividing it. Chin and throat silky white, the
feathers brown at the base; sides smoky-black, meeting in a narrow,
ill-defined line across the breast; medial belly white. Thighs,
under tail-coverts, and inner surface of wings smoky-black.
This delicately-formed little Swift, conspicuous even in flight,
from the broad belt of white across the black body, is a very
common species in Jamaica, where it resides all the year. Over the
grass-pieces and savannas of the lowlands, the marshy flats at the
seaward mouths of the valleys, as well as the pens of the mountain
slopes, this swift-winged sylph daily urges its rushing course in
parties of half-a-dozen to fifty or a hundred, often mingled with
other Swallows, performing mazy evolutions, circling and turning,
crossing and recrossing, now darting aloft, now sweeping over the
grass, till the eye is wearied with attempting to follow them. The
length of its wings, which is scarcely less than that of the whole
bird,—renders it a fleet and powerful flier; an attentive observation
will be able to identify it, when mingling in aerial career, by a
more frequent recurrence of the rapid vibration of the wings, the
momentary winnowing, by which a fresh impetus is gained. There is a
very interesting structure in the sternum of this bird, which as far
as I know is unprecedented. The sternum, though void of emarginations,
possesses two oblong foramina of large size, one on each side of the
middle of the ridge, and a round one perforating the ridge itself near
the front margin. As all three are closed by the usual membrane, the
object may be, the decrease of weight by the abstraction of bone,
while the surface for the attachment of the muscles of flight remains
undiminished. It would be interesting to know whether this structure is
found in the Collocaliæ of the Indian Archipelago, to which the present
bird bears a strong outward resemblance.
The stomach of one, a female, which I dissected, shot while hawking
among many others over Bluefields’ grass-piece, in April, was distended
almost to bursting with minute insects, which on being dispersed
in water, and examined carefully with a lens, proved, I believe
exclusively, the winged females of a small species of ant, exceedingly
numerous, all more or less comminuted.
On the 20th of March last, visiting in company with Mr. Hill the estate
called Dawkins’ Saltpond, the residence of the Spanish Admiral, at
the time of the conquest,—I observed several small Swallows flying
above some cocoa-nut palms; they uttered, as they flew, a continued
twittering warble, shrill but sweet, which attracted my attention. I
commenced a careful search, with my eye, of the under surface of the
fronds and spadices of one, and at length discerned some masses of
cotton projecting from some of the spathes, which I concluded to be
their nests. This conjecture proved correct; for presently I discovered
a bird clinging to one of these masses, which I shot, and found to be
this White-rumped Swift. On my lad’s attempt to climb the tree, eight
or ten birds flew in succession from various parts, where they had
been concealed before. The tree, however, was too smooth to be climbed,
and as we watched beneath for the birds to return, one and another
came, but charily, and entered their respective nests. Although several
other cocoa-nuts were close by, I could not discern that any one of
them was tenanted but this, and this so numerously, whence I inferred
the social disposition of the bird. At some distance we found another
tree, at the foot of which lay the dried fronds, spadices, and spathes,
which had been, in the course of growth, thrown off, and in these were
many nests. They were formed chiefly in the hollow spathes, and were
placed in a series of three or four in a spathe, one above another,
and agglutinated together, but with a kind of gallery along the side,
communicating with each. The materials seemed only feathers and
silk-cotton (the down of the _Bombax_); the former very largely used,
the most downy placed within, the cotton principally without; the whole
felted closely, and cemented together by some slimy fluid, now dry,
probably the saliva. With this they were glued to the spathe, and that
so strongly, that in tearing one out, it brought away the integument
of the spathe. The walls of the nests, though for the most part only
about a quarter of an inch thick, were felted so strongly, as to be
tenacious almost as cloth. Some were placed within those spathes that
yet contained the spadices; and in this case the various footstalks of
the fruit were enclosed in a large mass of the materials, the walls
being greatly thickened. All the nests were evidently old ones, for
the _Bombax_ had not yet perfected its cotton, and hence I infer that
these birds continue from year to year to occupy the same nests, until
they are thrown off by the growth of the tree. The entrance to the
nests, which were subglobular, was near the bottom.
Near the middle of May, my servant Sam, being engaged at Culloden, in
Westmoreland parish, cutting the fronds of the palmetto (_Chamœrops_)
for thatching, found these little birds nestling in abundance, and
procured for me many nests of the present season. Their recent
construction, and perhaps the diversity of their situation—for instead
of the hollow of a spathe, these were attached to the plaited surface
of the fronds,—gave them a different appearance from the former
specimens. Many of these I have now in my possession. They have a
singularly hairy appearance, being composed almost exclusively of the
flax-like cotton of the _Bombax_, and when separated, are not unlike a
doll’s wig. They are in the form of those watch-fobs, which are hung
at beds’ heads, the backs being firmly glued by saliva to the under
surface of the fronds, the impressions of the plaits of which are
conspicuous on the nests when separated. The thickness is slight in the
upper part, but in the lower it is much increased, the depth of the cup
descending very little below the opening. The cotton is cemented firmly
together as in the case of the others, but externally it is allowed to
hang in filamentous locks, having a woolly, but not altogether a ragged
appearance. A few feathers are intermixed, but only singly, and not
in any part specially. One specimen is double, two nests having been
constructed so close side by side, that there is but a partition wall
between them. Many nests had eggs, but in throwing down the fronds all
were broken but one, which I now have. It is pure white, unspotted,
larger at one end, measuring ¹³⁄₂₀ inch by ⁹⁄₂₀. The average dimensions
of the nests were about 5 inches high, and 3¹⁄₂ wide.
The genus _Tachornis_ seems intermediate between _Cypselus_ and
_Collocalia_, with considerable general resemblance to the latter. This
species is perhaps Hirundo 1, of Browne.