In the birds the length of the intestine is subject to great variations. The canal is short in species subsisting on fruits and insects, long in those feeding on seeds, plants and fish. The large intestine, immediately beyond the ileo-colic junction, is provided typically with two symmetrical lateral cæca which extend in some forms for a considerable distance cephalad on each side of the small intestine to which they are bound by peritoneal connections.

Fig. 333.—Buteo harloni, black hawk. Ileo-colic junction and cæca. (Columbia University Museum, No. 1502.)   Fig. 334.—Phalacrocorax dilophus, double-crested cormorant. Ileo-colic junction and cæca. (Columbia University Museum, No. 67/1534.)

As a rule carnivorous birds have short and rudimentary pouches (Figs. 333 and 334), whereas they are long in herbivorous forms (Figs. 335 and 336). Some carnivorous birds, as Corvus, Strix, etc., have fairly long cæca (Fig. 337). In the passerine birds living on seeds and insects, the cæca are of considerable length as they are also in some of the piscivorous divers ([Figs. 338] and [339]). They are long in the Ratitæ, and in the Lamellirostra, who feed chiefly on plants ([Fig. 340]).

Fig. 335.—Gallus bankiva, hen. Ileo-colic junction and cæca. (Columbia University Museum, No. 1486.)   Fig. 337.—Bubo virginianus, great horned owl. Ileo-colic junction and cæca. (Columbia Uni­ver­sity Museum, No. 672.)
Fig. 336.—Chen hyperborea, Canada snow-goose, Ileo-colic junction and cæca. (Columbia University Museum, No. 47/1448.)   Fig. 338.—Urinator lumme, red-throated loon. Ileo-colic junction and cæca. (Columbia University Museum, No. 1001.)
Fig. 339.—Merganser serrator, red-breasted merganser. Ileo-colic junction and cæca. (Columbia University Museum, No. 1798.)   Fig. 340.—Casuarius casuarius, cassowary. (Columbia University Museum, No. 1799.)
Fig. 341.—Struthio africanus, African ostrich. Ileo-colic junction and cæca. (Columbia University Museum, No. 48/1573.)   Fig. 342.—Ardea virescens, green heron. Ileo-colic junction and cæcum. (Columbia University Museum, No. 1132 a.)

The enormously elongated cæca of the African ostrich contain a spiral fold of the mucous membrane in the interior (Fig. 341).

In place of the usual double avian cæcum a single pouch is found in a few forms, namely in the Herons (Fig. 342).