FAMILY FORMICARIIDAE 121 



nigricristatus, but in dififering degree, so that it has seemed appropri- 

 ate to name them as separate races. The occurrence of Formicivora 

 grisea alticincta on several of the Perlas group in the Gulf of Panama 

 is more intriguing as the species grisea is not found on the mainland 

 of Panama, its nearest approach being the subspecies F. g. hondae 

 in northwestern Colombia, from the western shore of the Golfo de 

 Uraba (NecocH) eastward. 



The Formicariidae of Panama show the diversity found in the 

 family in South America. Smaller kinds range through the forest 

 canopy from the undergrowth upward, where they form a definite 

 part of the groups that forage through the branches in loose company. 

 (See Wiley, R. H., Auk, 1971, pp. 881-892.) Others, more secretive, 

 inhabit thickets, where their presence may be indicated by their calls 

 though the birds themselves remain hidden. Still others feed along 

 the ground, flying to higher perches only when startled, or to look 

 about. Several species are a regular part of the small groups of birds 

 that range with moving columns of ants to capture the small prey 

 flushed by these marauders. 



It seems evident that the various kinds have come to Panama since 

 the formation of the land bridge. It may be supposed that those of 

 terrestrial habit have spread northward slowly over and near the 

 ground. As a whole they form an appreciable part of the total avi- 

 fauna, most of them definitely attractive to the observer through 

 form and movement. 



KEY TO SPECIES OF FORMICARIIDAE 



1. Head with a definite crest 2 



Head without a crest 11 



2. Both back and lower surface barred with black and white, or black and 



buff 3 



Back and lower surface not heavily barred with black and white 4 



3. Bill large, swollen, maxilla strongly hooked at tip ; width at nostril equal to 



one-half length of exposed culmen ; crest without white. 

 Fasciated ant-shrike, Cymbilaimus lineattis fasciatus, 



male and female, p. 124 



Bill smaller, not appreciably swollen ; maxilla less strongly hooked at tip ; 



width at nostril less than one-half length of exposed culmen ; crest partly 



white Barred ant-shrike, Thamnophilus doliatus, male, p. 132 



4. Under surface mainly white ; larger, wing more than 80 mm. 



Great ant-shrike, Taraba major melanocrissus, p. 128 

 Under surface not white ; smaller, wing less than 80 mm 5 



5. Chestnut to rufous above, bright cinnamon-buff below. 



Barred ant-shrike, Thamnophilus doliatus, female, p. 133 

 Under surface blackish, gray, dull grayish buff, or streaked 6 



