The _Sylvicolidæ_ are essentially characterized among the Oscines with
nine primaries, by their small size, the usually slender and conical
insectivorous bill, shorter than the head, without angle in the gape
near the base; the toes deeply cleft so as to leave the inner one free
almost to its very base (except in _Mniotiltæ_), etc. The shallow
notch at the end of the tongue, instead of a deeply fissured tip,
distinguishes the family from the _Cærebidæ_, to some of which there
is otherwise so great a resemblance. The absence of abrupt hook and
notch in both mandibles separates it from such of the _Vireonidæ_ as
have nine primaries.
The American _Motacillidæ_ are distinguished from the _Sylvicolidæ_ by
the emargination of the outer and the great elongation of the inner
secondaries, as well as by other features referred to under that
family. _Anthus_, in particular, differs in the lengthened and
slightly curved hind claw. There is little difficulty in distinguishing
the _Sylvicolidæ_, however, from any families excepting the
slender-billed forms of the _Tanagridæ_, as _Chlorospingus_,
_Nemosia_, _Chlorochrysa_, etc., and the conirostral _Cœrebidæ_. In
fact, some ornithologists are inclined to include all three of the
families thus mentioned in one, from the difficulty of marking their
boundaries respectively.
In fact, we are of the opinion that no violence would be done by
adopting this view, and would even include with the above-mentioned
families the _Fringillidæ_ also. The order of their relation to one
another would be thus: _Fringillidæ, Tanagridæ, Sylvicolidæ,
Cœrebidæ_; there being scarcely any break in the transition between
the two extremes, unless there are many genera referred to the wrong
family, as seems very likely to be the case with many included in the
_Tanagridæ_. The _fringilline_ forms of the latter family are such
genera as _Buarremon_ and _Arremon_, they being so closely related to
some _fringilline_ genera by so many features—as rounded concave
wing, lax plumage, and spizine coloration—as to be scarcely
separable. Either these two families are connected so perfectly by
intermediate forms as to be inseparable, or the term _Tanagridæ_
covers too great a diversity of forms. With the same regularity that
we proceed from the _Fringillidæ_ to the typical forms of the
_Tanagridæ_ (_Pyranga_, _Tanagra_, _Calliste_, etc.), we pass down the
scale from these to the _Sylvicolidæ_; while between many genera of
the latter family, and others referred to the _Cærebidæ_, no
difference in external anatomy can be discovered, much less expressed
in a description.
In the following synopsis we attempt to define the higher groups of
the _Sylvicolidæ_, although in the large number of species and their
close relationships it is very difficult to express clearly their
distinctive features.
Subfamilies.
A. Bill conical, its bristles very weak, or wanting.
_a._ Bill sub-conical, the culmen and commissure nearly
straight.
Sylvicolinæ. Feet weak, not reaching near the end of the
tail. Wing pointed, considerably longer than the nearly even
or slightly emarginated tail. Feet dark-colored (except in
_Helmitherus_, _Helinaia_, and _Parula_). _Arboreal._
Geothlypinæ. Feet strong, reaching nearly to end of the
tail. Wing rounded. Feet pinkish-white. _Terrestrial._
_b._ Bill high and compressed, the culmen and commissure much
curved.
Icterianæ. Bill without notch or rictal bristles; wing much
rounded, shorter than the tail.
B. Bill depressed, its bristles strong.
Setophaginæ. Bill, _tyrannine_, considerably broader than
high, the tip more or less hooked, and with a distinct notch.
Rictal bristles reaching half-way, or more, to the tip.
Sections and Genera.