LARUS AEGENTATUS, HERRING GULL. 627 



Adult. — Bill rather less than the tarsus, shorter than the head ; robust, its heijjht at 

 the angle slightly more than at the base. Culmen nearly straight at the nostrils; (ben 

 rapidly convex to the stout, deflected, overhanging apex. Outline of rami slightly 

 concave ; gonys about straight ; eminence at symphysis large and prominent, but its 

 apex not very acute, '^'ings long-pointed ; the first primary always longest. Tail 

 even. Feet of moderate size; tarsi compressed, anteriorly scutellate, laterally and 

 posteriorly reticulate. Membranes full and broad, scarcely incised. Claws obtuse, 

 but little arched ; the inner edge of the middle one dilated, but not seriated. 



Breeding plumage. — Bill bright chrome, its tip diaphanous ; a vermiliou spot at the 

 angle, with sometimes a small black one just anterior to it. Legs and feet pale flesh- 

 color; the claws blackish. Mantle typical "gnll-blue," much lighter than in oeci- 

 dentalis ; lighter than in hrachyrhynchus ; of much the same shade as in delawarensis or 

 glaucescens ; darker than in j!a»c»« or teitcoptoMS. The bases of the ijrimaries are the 

 same as the back, or very slightly lighter, not so light, nor of so great extent (being 

 exceedingly short on the first primary), nor so broad at the end, as in californiais. On 

 the /rst primary this light basal portion is very short, hardly reaching within six or 

 seven inches of the tip of the primary. It is not lighter at its junction with the black, 

 nor does it extend further on the central portion than on the edge of the feather. On 

 the second, third, and fourth primaries the bluish of the basal portions of the feather 

 extends about the same djstacce on each (within four inches of the tip of the second), 

 and runs up further on the centres of the feathers than on their edges, and grows 

 nearly white at its junction with the black portion of the feathers. First primary 

 Kith a sutapical u-ltite spot near its tip; small, rounded, not much over an inch in diam- 

 eter ; generally not longer on the outer vane than on the inner ; sometimes wanting 

 on the former ; in oldest birds this spot enlarging to coalesce with the white tip of the 

 feather, but such state rarely observed; second primary usually without a subapical 

 spot, or if one is present it is very small. All the primaries with small rounded white 

 apices, and black from these apical spots to their bluish-white bases ; this band of 

 black growing narrower from the first toward the seventh, where it is a mere point. 



Winter plumage. — The head and neck are streaked with dusky. The bUl is less 

 brightly colored. Otherwise as in summer. 



Immature. — The feathers of the back have gray margins, and the upper wing coverts 

 are mottled with dusky gray. An imperfect subierminal bar of dusky on the tail. 



Young of first irinter.- Head, nek, and whole under parts more or less thickly mot- 

 tled with dusky, as are the wing-coyerts, secondaries, and tertials. The gull-blue of 

 the upper parts appears in irregular patches, mixed with gray. Eemiges and rectrices 

 brownish-black, with very narrow whitish tips, the former wanting both apical and 

 subapical white spots. Bill flesh-color, its terminal third black. Feet dull flesh-color. 

 Younger. — Entirely a deep dull brownish; the throat lightly streaked and the rump 

 transversely barred with whitish ; the feathers of the back with yellowish or grayish- 

 white edges; wings and tail'black; bill black; legs and feet dusky flesh-color. 



Dimensions of adult. — Length, 34 to 25 inches; extent, 54 to 58; wing, 17. '25 to 18.00; 

 bill along culmen, 2.40 ; height at nostril, 0.75 ; at angle, 0.80 ; tarsus, 2.75 ; middle toe 

 and claw the same. Female a little and young considerably less than the above. j 

 Other rariations. — These are very considerable as regards size and proportions. The 

 bill along the culmen varies from 2.55 to 2.20 inches, being, however, in adult birds, 

 generally very near the former measurement. The tarsus will vary more than a fourth 

 of an inch — from 2.75, its usual length, to about 2.40. The diiference in the length of 

 the wings is slight for so large a Gull, only about an inch. The younger the bird the 

 smaller it is, the weaker and shorter its bill, and the slenderer its feet. A'ery old birds 

 sometimes become almost abnormally big, as is the case with X. glauous and others. 



Between the time of leaving the nest and of assuming the complete plumaife of the 

 adult bird the changes are very great. AVhile the uniform dusky of the body is turn- 

 ing to pure white and clear blue, and while the black tail is whitening and the black 

 primaries are assuming their peculiar characteristic markings, the variations in degree 

 and extent of all the colors are endless. It is hardly possible to characterize any defi- 

 nite stages, as they glide insensibly into each other. But in adult birds, which have 

 attained their second or third summer, the colors of the whole body and the markinn-s 

 of the primaries are so constant that, taken in connection with the size, form, and 

 other pjirticulars, they afford fair varietal characters. I do not mean to assert that 

 there is no variation in these points, but that adult birds generally preserve a certain 

 definite pattern of coloration of the primaries. 



In this species this "pattern" may be summed up, briefly, as: The presence of a 

 black band on the first seven primaries, which takes in nearly the whole of the first, 

 and rapidly narrows until on the seventh it is a mere spot; bluish bases to all the 

 primaries, of a width iuverccly as that of the black portion; small white apical spots 

 on all the primaries ;* and a large rounded subapical white spot on the first (rarely 

 becoming confluent with the white apical spot), with or without a smaller one on the 

 second. 



* These may be absent, being worn off from very old feathers, just before the moult. 



