436 



BIRDS OF THE REPUBLIC OF PANAMA PART 4 



dilucida (Thayer and Bangs, Bull. Mus. Comp. Zool., 46, 1905, p. 157) 

 attributed to the Pearl Islands is likewise not discernable. Other races 

 of this species range to the Guianas, Brazil, and northern Bolivia. 



The Blue-gray Tanager is similar in behavior to the Palm Tanager 

 (T. palmarum) , with which it has been known to interbreed (Haver- 

 schmidt, Bull. Brit. Orn. Club, 1966, pp. 5-6). It feeds in vegetation 

 of every level, moving rapidly and often flying long distances from site 

 to site. Its food includes both animal and vegetable matter; 1 collected 

 by E. A. Goldman at Portobelo, Colon, contained bits of caterpillar 

 skin 18%, remains of a bug 6%, less of a small hymenopteran 1%, 

 orthopteran remains 5%, about 20 seeds imbedded in fiber, undeter- 

 mined 70%. Once at the Officers Club dining room at Albrook Field, 

 Canal Zone, I watched 1 at sunrise hover repeatedly under the eaves 

 searching for something; in the end it seized a half -inch-long spider 

 from the center of a 2-foot web and flew away. When feeding on 

 drupes, the birds squeeze them in the bill to extract part of the pulp, and 

 then drop the seed. Leek (Living Bird, 1971, p. 96) recorded that on 

 Barro Colorado Island, Canal Zone, Blue-gray Tanagers commonly ate 

 the fruit of Hamelia and Cecropia; 2 that he weighed there averaged 

 37.2 g (Bird-Banding, 1975, p. 203). Two males collected by Strauch 

 (Bull. Brit. Orn. Club, 1977, p. 65) weighed 31.5 and 32.0 g. 



Buskirk et al. (Auk, 1972, p. 620) found that at Cerro Punta, Chiri- 

 qui, Blue-gray Tanagers joined passing mixed species flocks, but usu- 

 ally did not follow them. Even when they are seen only in pairs or small 

 groups, Blue-gray Tanagers may be much more common in an area 

 than they seem. Once at Taboguilla Island, Panama, I called about 50 

 into two trees by squeaking. At night they often gather to roost to- 

 gether in large numbers; I have seen scores come into a few trees in 

 the evening, at Aguadulce, Code, in January, and Puerto Obaldia, San 

 Bias, in March, when one might presume them to be nesting. They 

 usually arrive in pairs. 



This is a noisy and sometimes belligerent species: at Volcan, Chiri- 

 qui, I once saw 1 dive repeatedly at a male Northern Oriole {Icterus 

 galbula) that tried to perch in a dead tree top over the forest. Eisen- 

 mann (Smiths. Misc. Coll., vol. 117, no. 5, 1952, p. 55) describes the 



necks retracted, which has the effect of making the mantle contrast more markedly 

 with the head. Carriker's specimens from Colombia, on the other hand, are more 

 loosely constructed and have the neck more extended, so the contrast between head 

 and mantle is less and consequently the overall appearance is somewhat lighter. 

 S. L. O. 



