517. 
809. 
72 SYSTEMATIC SYNOPSIS. —LONGIPENNES — GAVIA. 
73. Subfamily RHYNCHOPINA: Skimmers. 
= Bull hypogna- 
thous. Among 
the singular bills 
of birds that fre- 
quently excite 
our wonder, that 
of the skimmers 
is one of the most 
anomalous. The 
under mandible 
is much longer 
than the upper, compressed like a knife-blade; its end is obtuse; its sides come abruptly 
together and are completely soldered; the upper edge is as sharp as the under, and fits a 
groove in the upper mandible; the jawbone, viewed apart, looks like a short-handled pitch- 
fork. The upper mandible is also compressed, but less so, nor is it so obtuse at the end; its 
substance is nearly hollow, with light cancellated structure, much as in a toucan ; it is freely 
movable by means of an elastic hinge at the forehead. There are cranial peculiarities. Con- 
formably with the shape of the mouth, the tongue differs from that of other Longipennes in 
being very short and stumpy, as m kingfishers, and the Steganopodes. The wings are exceed- 
ingly long, and the flight more measured and sweeping than that of terns; the birds fly in close 
flocks moving simultaneously, rather than in straggling companies. They seem to feed as they 
skim low over water, with the fore parts inclined downward, the under mandible probably. 
grazing or cutting the surface; but they are also said to use their odd bill to pry open weak 
bivalve mollusks. The voice is very hoarse and raucous, rather than strident. They are 
somewhat nocturnal or at least crepuscular; their general economy is the same as that of terns, 
as are all points of structure excepting those above specified. Besides the following, there are 
only two species: R. flavirostris and R. albicollis, of Asia. 
RHYN'CHOPS. = (Gr. pvyyos, hrugchos, beak ; &, ops, the face; well applied to the bird 
whose beak is such an extraordinary feature.) SKIMMERS. Character as above. 
R. ni/gra, (Lat. nigra, black. Fig. 520.) Buack Skimmer. Adult ¢ Q: Bill with basal 
half carmine-red, rest black. Ivis hazel. Feet carmine-red, drying yellowish, with black claws. 
Crown of head, its sides to just below eyes, back of neck and whole upper parts, glossy 
jet-black. Forehead, sides of head below eyes, sides of neck and whole under parts, pure 
white, tinted rosy or creamy in the nuptial season. Lining of wings and the bordering 
under wing-coverts, black. Primaries black, with black shafts, their inner webs duller 
blackish, the inner four with inner webs and tips of both webs, white; secondaries white, 
with a space of dark color on outer and small part of inner webs, increasing in amount 
inwards, till the inner four are dark with only white tips. Tail-feathers white, the inner 
webs more or less obscured with dark brown. Length 16.00-20.00; extent 42.00-50.00 ; 
wing 13.00-16.50; tail 4.00-6.00, forked about 1.50; tibie bare 1.00; tarsus 1.45; middle 
toe and claw 1.30. Length of under mandible 3.50-4.50, of upper about 3.00; height opposite 
nostrils 0.65 ; width 0.45; gape 4.50 or more; fused tomia or gonys of under mandible 4.00 
or less; greatest depth of under mandible 0.60. Q smaller than g. Young at minimum 
dimensions given. Young-of-the-year: Bill smaller than in adult, thinner, weaker, its 
ridges less sharply defined, and the two mandibles of less unequal lengths. Bill brownish- 
black for three-fourths of its length, fading into dull horn-color just at its tip, lightening into 
more or less intense flesh-color, or light reddish, toward the base. The strize on the sides 
of the lower mandible are as numerous as, but much less distinct than, in the adult. Tail 
ON 
ae SO 
\Y . SY Oo Xe LQ 
RX 
Fig. 520. — Bill of Skimmer, nat. size. 
