FAMILY TYRANNIDAE 381 



thousands flying over the Rio Chagres. Eisenmann from April 8 to 

 21, 1969, found this the most conspicuous passeriform. They remain 

 common through the first 10 days in May. The latest record is a 

 male taken by Austin Smith, May 23, 1927, at Zegla, on the Rio 

 Teribe, Bocas del Toro, a specimen in the Havemeyer collection at 

 Yale. 



The habits of this species in its migrations may be a surprise to 

 naturalists familiar with it in the North. Here in Panama they are 

 seen regularly in flocks that fly in close formation like Cedar Wax- 

 wings. In the steady passage of flocks that I have seen in early 

 mornings following down the Rio Jaque in Darien they may change 

 to travel in straggling lines like those of migrating robins. When 

 these groups rest, usually they perch closely together. In early morn- 

 ing, birds that may be tired from a night flight often drop down on 

 lawns in the towns, or on open areas elsewhere. My own first sight of 

 them in Panama was on October 10, 1940, when a small group rested 

 in the short grass at the old Washington Hotel in Cristobal. While 

 they may be seen feeding as usual on flying insects, regularly flocks 

 visit the clusters of fruit on royal palms or gather in fig or berry- 

 bearing trees. When single birds are seen occasionally, they perch 

 partly hidden among leaves, instead of on the commanding lookout 

 points that they use in the North. At this season also they are silent, 

 as in many observations I have not heard one call. Once only has a 

 kingbird displayed a habit normal in the North when one pursued a 

 passing osprey which twisted and turned to avoid the attack. 



Their flights regularly cross the Gulf of Panama. 



Present records include islas San Jose, Rey, Saboga, Chapera, 

 Viveros, Taboga, Taboguilla, and Urava. They have been recorded 

 also in the mountains of eastern Darien at Cana on Cerro Pirre. 



Morton (Auk, 1971, pp. 925-926), in observations in the Canal 

 Zone in 1965-1966 and 1970, found kingbirds generally more plenti- 

 ful as migrants during the northward flight. In the fall migration 

 in September he recorded flocks moving southward at such high 

 elevations that they could be identified only through binoculars. He 

 believed that this seasonal difference in their migratory movement 

 was regulated by the availability of a food supply. In spring, in the 

 main they were fruit eaters, principally of the berries of the common 

 mangabe. Didimopanax morototoni, available in abundance at that 

 season. In fall, when berries were less available, they depended more 

 on insects, secured through greater effort. 



