NO. 2059. TAIL FEATHERS OF GIANT BORN BILL— WET MORE. 499 



The central feathers are identical in condition Avith those in the bird 

 immediately preceding except that the right rectrix is the longer and 

 yoimger as is shown by its color and condition as regards wear. 



Cat. No. 181250, U.S.N.M.; female; Makapan, East Sumatra, 

 February 20, 1907. The eight lateral tail feathers are present and 

 but one fully developed central feather on the right side, which has 

 the vane faded and broken below the distal extremity. On the left 

 its mate has grown out until it is 4^ inches longer than the lateral 

 rectrices. 



It wiU be noticed at once that in none of these nine birds which 

 have been critically examined are both feathers of the central pair 

 equal in length, apparent age, or development. In the three birds 

 (Nos. 181104, 181699, and 181249) in which both feathers are approxi- 

 mately the same length one of them is noticeably a feather of a pre- 

 vious molt which is about to be shed and which is so worn and abraded 

 that part of the shaft has been broken off, leaving it shorter than the 

 newer feather. The other specimens aU have one central feather fully 

 grown and the other at different stages of development from a newly 

 appearing pin feather barely projecting beyond the flesh to a bright 

 new feather more than three-fourths the length of its companion. 



From these facts it is evident that but one of these feathers is devel- 

 oped at one time. This feather grows to full length and is retained 

 at the next molt while another starts on the opposite side. When 

 this second feather attains its growth the two are found together 

 for a short time until the old rectrix is shed, leaving the newly devel- 

 oped feather as a projecting vane in the tail, when the process is 

 repeated. Curiously enough each new feather, whether on the right 

 or left side, grows out beneath the vane of the older feather, thus 

 securing protection from abrasion and fading until mature. 



The long feather is apparently dropped sometime between Decem- 

 ber and March, though I have not been able to ascertain the exact 

 time or the age which these feathers attain, as the nine birds studied 

 come from four separate localities, and different chmatic conditions 

 undoubtedly modify the breeding season and so change the time of 

 the post-breeding molt. However, between September and January 

 six birds are found to have these feathers of unequal length and in two 

 specimens collected in February the new feather is fuUy gro^vn and the 

 other still in its place, while signs of growth are present in the other 

 feathers, pointing to a duration of two years for each of these giant 

 rectrices, though it may be found that they are renewed at shorter 

 intervals, each one, however, being retained more than a year. It 

 is very evident that these feathers remain in position for more than 

 one year, from the great wear and fading which they show when com- 

 pared with the other tail feathers and the remiges. 



