980 SYSTEMATIC SYNOPSIS. — LONGIPENNES. 



S. longicau'da. (Lat. long-tailed. Fig. 083.) Arctic Jager. Long-tailed Jager. 

 Buffon's Jaeger. Arctick Bird ($) of Edwards, 1750, pi. 148, and sharing most of 

 the other names of the preceding species. Bill shorter than head, less than middle toe with- 

 out claw ; stout, compressed, higher than broad at base, its sides regularly converging. Ceral 

 portion of culmen broad, flat, depressed, slightly concave in outline, ungual portion very con- 

 vex to the greatly overhanging tip ; narrower than the ceral. Tomia of upper mandible sinu- 

 ate, at first concave and ascending, then convex and descending ; again very concave as they 

 decurve toward tip, just behind which there is an imperfect notch. Tomia of lower mandible 

 nearly straight to tip, where deeurved. Gonys short, slightly concave. Eminentia symphy- 

 sis acute, but not large ; rami long as compared with gonys, but absolutely rather short, 

 from encroachment of feathers. Cere very short, not longer than unguis (compare last spe- 

 cies). Encroachment of feathers on bill greater than in any other species ; on upper mandible 

 they extend within 0.50 of the distal end of cere, having a broad, rounded termination, the 

 feathers of the two sides meeting on and covering culmen some distance from its real base. 

 Feathers on sides of lower mandible extending nearly as far as on upper, and those between 

 the rami quite to symphysis. Wings long ; 1st primary much the longest, the rest rapidly 

 graduated. Tail longer, both absolutely and relatively, than in any other species, being half 

 as long as wings, graduated 0.75. Middle pair of rectrices exceeding wings ; projecting 8.00- 

 10.00 beyond the others, rigid at base, being there much stitfer than the other feathers, but 

 gradually becoming flexible, and at length filamentous. Feet quite slender ; tarsus equal to 

 middle toe and claw. Tibise bare of feathers for 0.75 ; reticulation of feet identical with that 

 already described under other species ; scutella in front of tarsus, however, showing a tendency 

 to degenerate into minute plates near tibio- tarsal joint. Proportions of toes as in other spe- 

 cies, but claws comparatively small and weak. Adult ^ '^ , \n breeding plumage : Occiput 

 decidedly subcrested ; lateronuchal feathers lengthened, with disconnected webs, but hardly 

 acuminate or rigid. Bill dusky, its nail almost black. Tarsi leaden-blue in life, drying some 

 indefinable color ; tibise, toes, webs, and claws black. Cap brownish-black, which color ex- 

 tends on cheeks, the feathers before and below eye and on sides of bill being of this color. 

 Neck all round, but especially the peculiarly-formed feathers on the lateronuchal region, 

 light straw-yellow. Whole upper parts, with upper wing- and tail-coverts, deep slate, 

 which, on primaries, secondaries, lateral tail-feathers, and distal half of central pair, deepens 

 into lustrous brownish-black. Under surface of wings and tail deeper slate than the back, 

 but not so deep as their upper surfaces. Chin, throat, and upper breast white, gradually 

 obscured with dark plumbeous, which deepens posteriorly, so that abdomen and under tail- 

 coverts are nearly as dark as back. Shafts of first two or three primaries pure white, turning 

 into brownish -black at tips ; of other primaries, and of tail-feathers (including central pair), 

 brown, except just at base, blackening terminally. Under surfaces of all the shafts white for 

 nearly their whole length. Chord of culmen 1.15; gape 1.70; cere 0.60; unguis about the 

 same ; gonys 0.30; from feathers on sides of bill to tip 0.90 ; wing 12.50 ; tail 6.25, its mid- 

 dle feathers 14.00 to 16.00, projecting 8.00-10.00; tibise bare 0.75; tarsus 1.60; middle toe 

 without claw 1.40. In bulk of body this species is decidedly less than ^S*. parasiticus ; but the 

 extreme elongation of the middle tail-feathers makes its total length as much or even more — 

 up to 2.3.00 in some cases. The changes and states of plumage are identical with those of the 

 preceding species, though the melanotic phase is extremely rare (Ibis, 1865, p. 217). Adults 

 of the two species, with fully grown tail-feathers, cannot be confounded, but it is usually diffi- 

 cult to distinguish young birds : observe the small size, and some differences of proportions 

 above described, especially the short cere ; and in general a more ashy or grayish tone of the 

 plumage. Eggs not distinguishable ; averaging smaller, but dimensions overlapping ; a fair 

 specimen is 2.10 X 1-50 ; from this down to 1.90 X 1-40. This Jaeger, like the last, inhabits 

 the Northern Hemisphere, but is on the whole more northerly, breeding chiefly within the 



