190 Papers from the Marine Biological Laboratory at Tortugas. 



work of this kind is more or less " impressionistic," the attempt is here 

 made, while the material is still fresh in my mind, to enumerate some of the 

 more important problems to be found in the study of these birds and to set 

 forth my tentative efforts to solve them. 



OBSERVATIONS UPON THE INSTINCTS AND HABITS OF TERNS DURING 



THE NESTING SEASON. 



A GENERAL DESCRIPTION OF THE TWO SPECIES OF TERNS. 

 THE NODDY TERN (ANGUS STOLIDUS). 



The noddy tern is described by Saunders, ^ as follows : 



Adult Male in Breeding Plumage. Forehead nearly white at the base of the bill, 

 passing on the crown into lavender-gray, which deepens on the neck into lead color; 

 lores and orbital region black with a faint whitish superciliary streak; upper parts 

 chiefly dark-brown, the primaries, tail feathers, and their shafts nearly black; under- 

 parls dark brown on the abdomen and breast, passing into deep lead color on the 

 throat; bill blackish; tarsi and toes reddish-brown, fully webbed, webs ochraceous. 

 Total length about 16 inches, culnien 2.1, wing 10.25 to II, tail 6 to 7, the fourth 

 feather from the outside the longest, tarsus i, middle toe with claw 1.55. 



Adult Female. Very similar, but as a rule somewhat browner on the shoulders 

 and with less lead color on the throat, slightly smaller and with a weaker bill." 



Hab. Tropical and juxta-tropical America; chiefly on the Atlantic side, but also 

 on the Pacific in Mexico and in the central region; Atlantic down to Tristan da 

 Cunha (breeding); intertropical African and Asian Seas, up to Yeddo ; Australasia 

 down to about 35 S. ; Islands of the Pacific up to Laysan, etc., and as far as Sala y 

 Gomez, 105 W. ; also Chatham I., Galapagos (fide Ridgway), but not on the coasts 

 of Peru or Chile. Breeding, as a rule, where found. Once obtained off the south 

 coast of Ireland. 



THE SOOTY TERN (STERNA FULIGINOSA). 



Rothschild's^ description of the sooty is as follows : 



Adult. Forehead, sides of head, and entire lower parts, including lower wing 

 coverts, white with a very delicate bluish tinge on the abdomen under wing-coverts 

 and under tail-coverts when the birds are alive or quite fresh. Lores and upper parts, 

 including the hind neck [which is whitish in H. anoestheta (Scop)], uniform sooty 

 brown. Primaries black, but the shaft and outer web of the first primary white 

 below, except on the outermost tip. Tail-feathers sooty-black; all the shafts white 

 below, and the shafts of the outer pair, as well as their outer web and basal part of 

 inner web, white. Total length about 17 to 17.5 inches, wing 11.6 to 12, outer rec- 

 trices (if not abraded) 7.5 to 8, central pair 3, culmen 1.7 to 1.8, tarsus 0.85. (Speci- 

 mens from America and Kermadec Islands are exactly similar.) Iris dark-brown, 

 bill and feet black. 



Hab. Tropical and juxta-tropical seas, breeding wherever suitable islands and 

 reefs exist; occasionally wandering to Maine in North America, and to Europe, even 

 as far as England. Almost unknown on the South American side of the Pacific; 

 otherwise very generally distributed. 



^ Catalogue of the Birds of the British Museum, vol. xxv, pp. 136 140. 

 "I could not find any difference in appearance between the males and females. 

 The two sexes in life arc indistinguishable. This applies to both noddies and sooties. 

 ''Avifauna of Laysan, etc., p. 39. 



