28 



BIRDS OF THE REPUBLIC OF PANAMA— PART 4 



been reported regularly, although numbers vary greatly from year to 

 year. The earliest specimens known from the Republic are 2 males 

 collected by R. R. Benson near Tocumen, eastern Province of Panama, 

 August 21, 1931 (received by the Smithsonian in a collection presented 

 in 1954). 



The main group of migrants appears to arrive in the last week of 

 April or in early May (with one seen by me April 5, 1954, at Pedro 

 Miguel, Canal Zone, as an early date). Sometimes in late April flocks 

 of hundreds can be seen in the Caribbean side of the Canal Zone. The 

 birds are present in numbers through September, with a few remaining 

 later (18 seen October 26, 1955, by J. E. Ambrose). They have been 

 recorded most commonly in open areas of the Canal Zone, and the 

 adjacent Province of Panama and also west to western Chiriqui. At 

 evening they may join Gray-breasted Martins to spend the night in 

 communal roosts. 



Eisenmann reports seeing them commonly during June, July, and 

 August in some years on the Pacific slope of western Panama, includ- 

 ing Code (Penonome, Anton), Veraguas (near Santiago), Chiriqui 

 (Remedios, David, and many other lowland localities). On the Carib- 

 bean slope he observed several as far west as Changuinola, Bocas del 

 Toro, on June 30, 1956 (N. G. Smith noted 3 or 4 there on September 

 3, 1964) and as far east as Rio Piedras, Colon. There seem to be no 

 reports from the Azuero Peninsula, San Bias, or Darien, but this prob- 

 ably indicates absence of observers in open areas during the season of 

 occurrence. 



In August 1954 Eisenmann found them exceptionally abundant in 

 open areas — greatly exceeding in numbers the aggregate of all other 

 swallows seen; flocks of several hundreds often perched together on 

 wires, and thousands had been noted in one day (August 9 in Code). 

 By early September, numbers were much reduced, although Major 

 Chapelle noted as many as 80 on September 18 on the Pacific slope of 

 the Canal Zone, but numbers kept dropping until he saw his last Brown- 

 chested Martin that year on October 16 (a lone bird perched with 

 Gray-breasted Martins). Although Eisenmann has observed this 

 species in Panama (since he first recognized it in 1949) whenever he 

 has visited that country from May through early September, he has 

 never seen numbers approaching those in 1954. In 1972 (August 2-4) 

 Ridgely reports seeing flocks of hundreds around El Llano near the 

 Bayano River in eastern Province of Panama. He saw 5 on January 

 2, 1974, west of Rio Hato, Code— evidently birds that had failed to 

 migrate to the breeding grounds. 



