FAMILY ARDEIDAE IO3 



is typical of this subspecies. Two adult birds and one in its second 

 year, from the mouth of the Rio Pay a on the upper middle Tuira, 

 appear somewhat intermediate toward caliginis, for although the bill 

 at the nostril is slender it is somewhat more swollen toward the tip. 

 They are, however, to be placed with the South American form. The 

 three birds from the Paya were collected by the staff of the Gorgas 

 Memorial Laboratory on April 11 and 15, 1959, a month after I had 

 left the area. As I did not record the species here during February 

 and March it is possible that they had come into the region from 

 elsewhere subsequent to my departure. 



A female collected by Wedel at Perme, May 31, 1929, a bird in a 

 plumage that lacks perhaps a year of being fully adult, agrees with 

 the Paya specimens in slender bill and dark coloration. Another, an 

 adult male, from Puerto Obaldia secured by the same collector Dec. 

 8, 1931, also is similar. 



HETEROCNUS MEXICAKUS (Swainson): Bare-throated Tiger-Bittern; 



Jorralico 



Figure 16 



Tigrisoma mexicamis Swainson, in Murray, Encyclopedia of Geography, July 

 1834, p. 1383. (Mexico.) 



Throat and upper foreneck bare of feathers, a character, found 

 even in the young when first hatched, that distinguishes this species 

 in any plumage from the banded tiger-bittern. 



Description. — Length 710 to 810 mm. Adult, crown and nuchal 

 crest black; under surface dull cinnamon brown, with the foreneck 

 streaked broadly with black and white ; sides of neck and upper sur- 

 face finely barred with blackish and buffy white, with shaft streaks of 

 dull black on back and wings. 



Immature, boldly barred throughout with dull cinnamon-buff and 

 black; sides and under surface of wings white, barred with black. 



In an incubating bird at a nest with 3 eggs northwest of Puerto 

 Madero, Chiapas, Walter Dawn (Auk, 1964, p. 231) records colors 

 as follows : Iris deep yellow ; bare loral stripe greenish yellow ; bare 

 skin of throat bright yellow ; tarsus greenish slate. 



Measurements. — Males (12 specimens, Mexico to Panama), wing 

 330-372 (344), tail 126-142 (136), culmen 100.0-118.0 (111.4), 

 tarsus 104.6-115.0 (111.6) mm. 



Females (15 specimens, Mexico to Panama), wing 316-365 (338), 

 tail 112-153 (131.0), culmen 96.4-112.0 (104.6), tarsus 96.8-114.0 

 (108.4) mm. 



