Vol. XVIII 

 190 1 



I DvviGHT, Moults and Plutnages oj Gulls and Tertis. C I 



ages are made up of parts of several earlier ones, a fact that has 

 given rise, no doubt, to the old idea that a color change was in 

 progress. 



It may be well to briefly outline the order of renewal in the 

 Laridae although it does not differ materially from that of other 

 groups of birds. The dorsal feathers at the root of the neck are 

 apt to be the first to show renewal, but almost simultaneously new 

 feathers begin to appear on the humeral tracts, on the anterior parts 

 of the head, at the sides of the breast, on the flanks and at fresh 

 points on the back, the new growth tending to spread backwards 

 from these initial points with some indication of alternate feather 

 replacement. New feathers begin to show along the cubital borders 

 of the wings, and the proximal primary is lost early in the moult. 

 The others fall in succession, the inner primaries more rapidly than 

 the outer, and each gains nearly full length before the next is 

 lost. When only three or four remain, the distal secondary suc- 

 cumbs to moult, followed rapidly by the others, so that the proxi- 

 mal is lost before the distal primary is fully grown. The growth 

 of this primary marks very nearly the completion of the moult, 

 although the rectrices are often a little later, the middle pair falling 

 usually coincidently with the distal secondary, followed by adjacent 

 pairs, except that the outer pair may precede the one adjacent and 

 that almost the whole tail may be lost at once in some cases. The 

 last feathers to be renewed may be found at many points, especially 

 on the forehead, nape, interramal space, posterior parts of the body 

 and in the median wing-coverts. If the moult be partial only the 

 back, head and neck are affected, together with, perhaps, the cubi- 

 tal borders of the wings and the tertiaries, and sometimes appar- 

 ently little more than the anterior part of the back succumbs. It 

 is important to know the relative order in feather growth because 

 partial moults, beginning at the same points as complete ones, 

 extend somewhat irregularly for only a limited distance from them. 



All of the species of Gulls and Terns appear to belong to the 

 class of birds in which the adults moult twice every year. The 

 Terns undergo two complete moults in a year and while the Gulls 

 also undergo two, the prenuptial is incomplete and never includes 

 the remiges and rectrices, or the wings and tail. Further than this, 

 two groups of Gulls maybe recognized, (i) the smaller species 



