A finely-plumaged male bird of Falco cyaneus (L'Oiseau St. Martin):,,,fin the
Paris Museum, had the proportions of the quills as follows: first equal to the
seventh ; the second half an inch shorter than the fifth ; the third a slight degree
shorter than the fourth; which was the longest of all. The under plumage was pure
white, the tail hardly rounded, and the two middle feathers slightly shorter than
the rest. The two most adult of our male specimens (Nos. 1 and 3) very closely
agree in these dimensions, except, indeed, that the difference between the third
and fourth quill feathers is not very apparent; but we cannot, on this account
alone, consider them identical, for precisely the same characters are equally apparent
in the Circus histrionicus of Quoy and Gaimard (Busard bariole, Mus. P ar.),
a bird somewhat smaller, and barred beneath with rufous, but in general disposition
of colours, and length of wings and tail, closely resembling C. cyaneus. On the supposition that the whole of our specimens belong to one species,
(a fact, however, which cannot be proved,) we shall now give the,relative lengths of
the quill feathers in what appears a young male (No. 7). First quill feather intermediate
in length between the sixth and seventh ; second equal to' the fifth; third
equal to the fourth, which are the longest. It thus appears that even in characters
upon which we may generally place some reliance, individuals of the same species
will materially differ. European specimens in the French Museum of Circus
cyaneus exhibit the third and fourth quills equal; and this is also apparent in some
of those collected in America. We must, however, notice a specimen which presents
a considerable deviation from the rest; it is a Bear Lake specimen (No. 8),
killed in the autumn, and exhibits a general resemblance to the other two procured
there, but the colours of its plumage, deep liver-brown above and rust-coloured
below, are considerably darker. Its sex was not ascertained, but it was probably
a female, the other two being males ; and it may have been a yearling bird, not
above three months old, while the others, having been killed in May, must have
been birds at least as old as the preceding season. In it the second quill feather
is a very little shorter than the fifth, and an inch and three-quarters longer than
the sixth : the relative lengths of the other feathers correspond with No. 7, above
mentioned. No great stress can be laid on the difference exhibited by this specimen
in the clearness and brightness of its colours, for this is generally a mere
•indication of youth. In most of the Falconidce that are variegated, either with
brown or rufous, the colours are most intense in youth, and gradually become paler
or disappear with advanced age; but the total absence of the festoon or obsolete
tooth, in the upper mandible of this bird, is somewhat remarkable. We know
not of any instance that would lead us to believe this deficiency to be the mere
effect of age, and it seems extraordinary that a structure so apparently essential
should not be developed at the timè nature intends the bird should seek its own
sustenance. It has, indeed, been observed that the bill of the Falco Islandicus is
sometimes destitute of a notch ; and although we have attempted to account
for this variation, still it is by no means certain that this may not indicate a
difference of species. That there is some ground for this supposition, it may
be as well to mention that, although the difference between C. cyaneus and cim-
raceus may be very well drawn from the structure of the wings, yet that a more
important distinction between them has been overlooked. In cyaneus, the festoon
of the upper mandible is fu lly developed, and distinctly apparent, during every age of the bird, whether male or female ; while in C. cineraceus this festoon is absolutely
wanting in every specimen we have examined, in all of which the commissure
of the bill perfectly resembles that of the bird before us (No. 8). Nevertheless,
from the following differences in the structure of their respective wings, we do not
feel justified in considering them as of the same species :—
Falco cineraceus, a -perfect adult bird, in the Bird No. 8, above mentioned.
Paris Museum (Busard Montagu). ■
First'quill feather, equal to the sixth ; First, intermediate between the sixth and
seventh ;
Second, in the least degree longer than the Second, half an inch shorter than the fifth ;
fourth ;
Third - the longest ; Third and fourth, equal and longest ;
Fifth, intermediate in length between the first Fifth, a very little longer than the second,
and second.
To illustrate further the variation in the wings of the young and adult birds of
this group, the following measurements were taken from a male bird of the first year
(avant la premiere mue), belonging to C. cineraceus, and now in the Paris Museum.
First quill feather intermediate between the sixth and seventh ; second equal to
the fifth ; third shorter than the fourth, which is the longest. The colours of this
specimen assimilate very closely to our bird (No. 8), and tend to show that the
latter is a bird of the first year. Like ours, it is almost entirely of a bright rufous
beneath, without any other indications of those stripes, which are afterwards apparent,
than a dark line down the shaft of each feather.
Adult specimens of cineraceus, brought from India by M. Sonnerat, exhibit the
following variations : Male. First quill much shorter than the sixth, but intermediate
between the sixth and seventh ; second rather shorter than the fourth j
third the longest ; fourth longer than the second. Female. First quill feather
i 2