THAMNOPHILINAB.
We have already shown that in Nilaus, Sw., we have a form so nearly approaching
to this sub-family, that we may fairly conclude on their approximation. The birds
composing this division are typically known by a strong, but considerably more
lengthened bill, bent only at the end, where the inflection is abrupt: the tooth,
also, is much less developed, although in some species it is still very prominent.
The feet are more robust; but the claws, no longer fine or attenuated, are now
broad and thick : above all, the economy of these birds is totally different from
that of the true Shrikes. They are described, both by Azara and Le Vaillant, as
living and searching for their prey among thick foliage ; hence their familiar name
of Bush Shrikes. Their wings for this purpose are but little used ; and we
accordingly find these members particularly short and feeble ; while the tail is
somewhat lengthened, and more or less rounded.
We consider the Geai longup of Le Vaillant* (G. Platylophus, Sw,,) as representing
that form in the circle of Thamnophilinm which conducts us to Malaconotus,
Sw., the first typical genus at which we arrive. The plumage of these richly-coloured
birds is generally vivid; composed of yellow, green, or crimson, blended with black
or green; while some few are clothed in the more simple colours of the American
type. Much difference is observed in the proportionate strength of their bills; and,
in some, the anterior toes are as much united as in the corresponding group of the
Pittce, or Short-tailed Thrushes, which these birds obviously represent among the
Shrikes. This variation in the structure of the feet takes place, however, in species
so nearly related, that it affords no ground for generic distinction. To this group succeeds
the American genus Thamnophilus, Vieil., known at once by the rictus being
invariably smooth ; the whole organization (excepting, perhaps, the bill) is also
much weaker. It is among these we find that close approximation to the Myotherce,
or Ant Thrushes, to which we have elsewhere alluded, and which is certainly so
close, that we ourselves for a long time suspected it to be a circular relation of
affinity. Whether such may not eventually prove to be the case, time alone can
show ; but the following are our reasons for considering the groups as belonging
to different families—observing, however, that their relation may be cited as
* We cannot discover to what genus our nomenclators have consigned this bird. It is the Garrulus gallericulatus
of the Ehcy. M£th.; but in the Paris Museum it is placed, with much more propriety, among the Malaconoti. There
can be little doubt of its being the scansorial type of its own sub-family.
one of the most remarkable instances of collateral affinity that the whole circle of
ornithology can produce. We must premise, that the apparent essential distinction
between the Ant-Thrushes (Myotkerinas) and the Bush Shrikes (Thamno-
philinw) is this: that the former seek their food upon the ground, and are ambulating
birds ; while the latter confine themselves to bushes, and are arboreal.
This difference in economy is consequently marked by a corresponding difference
in the structure of the feet. Those of the Myotherinee (including Drymophila, Sw.,
and certain Urotomi,' Swi)l;* have the tarsi much more elongated ; the claws
slender, and not fully curved ; and the lateral scales of the tarsi (excepting in one
form, which cannot possibly be confounded with Thamnophilus) uniformly entire *. The American Thamnophilinm, on the contrary, both in the typical group and
in the sub-genus Formicivora, have the tarsi shorter, the claws thicker and more
curved, and the lateral scales of the tarsi divided into numerous pieces. Near,
therefore, as is the approximation between these two groups, we have chosen, for
the present, to keep them distinct; but so far from wishing to bend Nature to our
own views, we shall put the reader in possession of our own doubts on the subject.
First, it may be said, that even admitting the distinctions of the tarsi, as above
stated, to be invariable, still the argument simply amounts to this—that Nature
has chosen to mark the real transition from the Thamnophilinm to the Myotherinw, in this manner; in proof of which, we have species of Formicivora with remarkably
short tails, and with tarsi fully as long as in several Drymophilce. Upon what
grounds, therefore, are we to believe that a relation, to all appearance so perfect as
that between Thamnophilus and Myothera, is to be called an analogy ; when, had
it been consistent with our views to include both in the same family, or to place
them at the confines of two families, we should have been fully justified in calling
the series a most perfect and unbroken line of affinity? Again; is it not a violation
of Nature to include such small, weakly-constructed birds as Formicivora (some of
which are scarcely larger than the Gold-crested Wren) in the same group with
birds so large and powerful as the true Thamnophilihce ? Thirdly, if this latter
objection is overruled by the reply, that size cannot enter into generic characters,
upon what principle is the little Pipra albifrons of the old authors separated from
these latter birds (Formicivora), when it appears actually to form a passage to
Prionops, Vieil., one of the groups of Bush Shrikes ?
* We here allude only to such species as we have elsewhere described ; since no birds require more investigation
than the small Myothera of modern ornithologists : they present some beautiful forms of analogy, representing every
family in the circle of the Dentirostres : even the Australian genus, Malurus, has its counterpart among these pigmy
Shrikes. An undescribed species now before us, is a perfect representation of Laniellus, Sw.; while others, by their
depressed bill, typify the Todies and the Flycatchers.