. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. 2. Variation in the size of the casque of Oreop/ios/s derbianus. Left: fully developed, and right: partly developed casque. (no casque) inhabits New Guinea, the western Papuan Islands and the Aru Islands, and insolifus (with casque) is found on the Bismarck Archipelago (Cain, 1954). That the casque and fleshy protuberance are no more than species-specific recogni- tion marks is further suggested by tlie func- tion of the white frontal shield of the coot Fulica americana. The sliield is an exten- sion of the rhamp
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. 2. Variation in the size of the casque of Oreop/ios/s derbianus. Left: fully developed, and right: partly developed casque. (no casque) inhabits New Guinea, the western Papuan Islands and the Aru Islands, and insolifus (with casque) is found on the Bismarck Archipelago (Cain, 1954). That the casque and fleshy protuberance are no more than species-specific recogni- tion marks is further suggested by tlie func- tion of the white frontal shield of the coot Fulica americana. The sliield is an exten- sion of the rhamphotheca over the fore- head, surmounted by tlie reddish callus. Gullion (1951) succeeded in producing larger shields by implanting testosterone subcutaneously. He showed that the shield is used in aggressive territorial displays, and that "paired birds are able to recognize their mates by the shape of the ;. Fig. 3. Lateral view of the head of Crax tomentosa. This species has neither casque nor elongated crest feathers. 2) Crest Feathers All birds of the genus Crax, except to- mentosa and pauxi, have elongated and erectile crest feathers (see Fig. 21, showing adult C. viitu with flattened feathers and young with erected feathers). In the rubra species-group these feathers are curled for- ward. Three species, mitti, salvini, and urumutum (see Fig. 21, and Figs. 4 and 5) have elongated but not curly crest feathers. In Penelope the crest feathers are erectile and straight (see Fig. 6), sometimes short, and only slightly longer than ordinary feathers of the pileum. In the pipile and jacucaca species-groups, however, the feath- ers are more elongated and have fewer barbs (decomposed) than in other species, and are also more conspicuously colored. All other cracids have ordinary short crest feathers. There is a tendency for an inverse corre- lation between the presence of elongated crest feathers and the occurrence of wattles or areas of naked skin on the throat. Mos
Size: 2067px × 1209px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorharvarduniversity, bookcentury1900, booksubjectzoology
