FAMILY CATHARTIDAE 153 



lists 5 eggs from Cuba as decidedly smaller and smoother shelled 

 than those of the Ruddy Duck, in color pale buff to buffy white, 

 SHbelliptical in form, with measurements 53.7-55.6x40-41.6 mm. Per- 

 sons living near the haunts of the pato tigre in Panama say that it 

 makes a nest among rushes and that it lays 4 to 6 eggs. At Juan 

 Mina Enrique van Horn told me that he had seen a parent with 5 

 young about the first of December 1955. On December 12 I shot 

 a male in breeding condition that had the intromittent organ much 

 enlarged, with blackish, spiny papillae around the base. 



The skin over the neck and upper breast in these birds is loose, 

 thickened with fatty tissue, and full as it is in the ruddy duck, and like 

 that species the syrinx in the male is simple without the enlarged 

 bulb found in males of most ducks. The esophagus, when inflated 

 with air, has an elongated sac near the center that is 25 mm. in 

 diameter. The trachea is enlarged at the upper end, and there is a 

 small elliptical aperture here on the ventral surface that opens into 

 a rounded, thin-walled sac, about 10 mm. in diameter when inflated. 

 There is also a somewhat larger extension that opens from another 

 aperture on the dorsal surface of the trachea. Evidently these have 

 some relation to a similar larger sac found in the male ruddy duck 

 (Wetmore, Proc. U. S. Nat. Mus., vol. 52, 1917, pp. 479-482). These 

 openings in the trachea of the masked duck were described many 

 years ago by von Pelzeln (Orn. Brasiliens, 1870, p. 321) who, how- 

 ever, seems not to have detected the air-sacs into which they led. 



Call notes have been described for the masked duck, but in my 

 experience with these birds they have been silent. They are hunted 

 to some extent, but they do not fly as much as the true game species. 

 Shooting, however, has reduced their numbers. 



At present the masked duck is recorded from the Caribbean drain- 

 age only on the Rio Chagres. It is probable, however, that it is found 

 near Changuinola, in Bocas del Toro, as these birds are known to 

 wander extensively. 



Order FALCONIFORMES 



Family CATHARTIDAE : American Vultures ; Buitres Americanos 



The birds of this family, of large size, known everywhere as 

 carrion-eaters, have the head and neck bare, or with only a scanty 

 growth of short down or hairlike feathers. The seven living species are 

 found only in the Americas, where they range from temperate 

 regions in the far north and far south, and the higher mountains, 

 throughout the warmer central areas, with their greatest abundance 



