FAMILY PHAETHONTIDAE 49 



world. They are guIl-Hke in general form, marked by the long 

 slender plumes of the central tail feathers, which, when fully grown, 

 exceed the length of the head and body, Panama has the only 

 breeding colony of one species, the red-billed tropicbird, in the whole 

 of Central America. 



PHAETHON AETHEREUS MESONAUTA, Peters: Red-billed Tropicbird, 



Rabijunco 



Figure 9 



Phaethon aethereus mesonauta Peters, Occ. Papers Boston Soc. Nat. Hist., vol. 

 5, Apr. 15, 1930, p. 261. (Swan Cay, oflf Isla Colon, Bocas del Toro, Panama.) 



Gull-like in general form, with greatly elongated central tail 

 feathers. 



Description. — Length 760 to 880 mm. (including the fully de- 

 veloped central tail feathers) ; white, often tinged lightly with pink; 

 upper surface irregularly barred with black; lengthened middle tail 

 feathers, including shaft, white. Plumage firm and compact. 



Iris brown ; bill red ; tarsus and basal half of toes dull yellowish- 

 buff ; end of toes, with connecting sections of webs and claws black. 



Measurements (from Murphy, Oceanic Birds S. Amer., 1936, p. 

 798). — Sexes alike (18 specimens from American localities), wing 

 293-317 (305), tail (normal feathers) 94-115 (105), (central tail 

 feathers 428-658), exposed culmen 60-66 (63.2), tarsus 26-29 (27.8) 

 mm. 



Resident. Nests on Swan Cay in the Caribbean off Isla Colon, 

 northeast of the entrance of the pass Boca del Drago. The birds fly 

 out over the sea to feed but apparently do not range far. 



Swan Cay, approximately 70 meters long, is a rounded quarter 

 moon in shape, pierced by two openings through one end, and rises 

 55 meters at the highest point. On the southern side, sheltered from 

 the northeastern trade winds, there is a small sandy beach below a 

 higher level area. Bushes and other vegetation cover the summit, and 

 there is a small clump of coconut palms at the low end. On January 

 26, 1958, as Thomas Dunn and I, traveling in his fishing boat, ap- 

 proached the island a tropicbird passed high overhead, and presently 

 others circled among the brown boobies that flew out as we came 

 near. The tropicbirds soared easily, with long tail streamers un- 

 dulating in the wind, graceful and attractive in every way. On the 

 leeward side of the islet several rested on nests placed on narrow 

 ledges on the rock faces above the sea, where they were sheltered 

 by overhang above. Some were low down, a meter or two above the 



