FAMILY CORVIDAE 



43 



172.0-198.0 (185.1, average of 6), culmen from base 40.6-427 ( 41.6), 

 tarsus 46.4-52.2 (48.5) mm. 



Resident. Fairly common locally through the lowlands of Bocas 

 del Toro, from near the Rio Sixaola west to Chiriqui Grande. 



Brown Jays range usually in small bands, in the borders of open 

 forest and second growth; they are not found in extensive stands of 

 heavy forest. Commonly they move about under cover among leafy 

 branches where they may not be noticed. They often fly out singly, 

 however, or as a group across open areas, calling loudly and making a 

 sharp popping sound through quick inflation and deflation of the curi- 

 ous air sac exposed on the upper breast. Lawton (in Jansen, 1983, 

 Costa Rican Natural History, pp. 573-574) reports that flocks use 8- 

 to 10-ha home ranges, defending a territory within the home range 

 only when breeding. The limited area where the species is known at 

 present in Panama marks the southern extension of the species, which 

 is found on the Caribbean slope of Central America, north to north- 

 eastern Mexico in Nuevo Leon and to extreme south Texas. It crosses 

 to the Pacific slope only in northwestern Costa Rica. 



Adult individuals have the bill and feet black. In immature birds 

 these areas are yellow to partially black, the pattern varying apparently 

 according to age. 



Lawton (in Jansen, 1983, Costa Rican Natural History, pp. 573-574) 

 found that in Costa Rica young members of the flock help build the 

 nest and will occasionally sit in it, but their efforts are irregular. The 

 number of females that contribute eggs to the nest or take part in incu- 

 bation varies. In one case where more than one bird was known to have 

 contributed eggs to the nest, only one bird was seen to incubate or 

 brood. The average clutch size of 30 nests examined by Lawton was 

 4.5, nearly twice that reported by Skutch (Pacific Coast Avif., no. 30, 

 1960, pp. 231-257), further suggesting wide variability in the breeding 

 habits of this species. 



In Guatemala, Skutch recorded a single brood each year, beginning 

 in February and March. The nest site was in trees in pastures or in 

 recent second growth, with the nests high and inaccessible near the tips 

 of long, slender branches. Other locations were in high forks in trees, 

 and in the crowns of banana plants. The bulky nest is made of sticks, 

 with a shallow cup lined with long, fibrous roots pulled by the birds 

 from the earth. Construction, by both male and female, is accompanied 

 by much calling. Lawton and Lawton (Auk, 1980, pp. 631-633) have 

 shown that critical factors in nest-site selection are protection from 

 wind and isolation from predators. Thus, the birds seek sites relatively 



