( 115 :) 
V. — The Moulting of the King Penguin (Aptenodytes patagonica). By Professor 
J. Oossar Ewart, F.R.S., and Dorothy Mackenzie, F.S.Z.S. (With Two 
Plates.) 
(Read November 15, 1915. MS. received January 23, 1917. Issued separately June 14, 1917.) 
CONTENTS. 
PACK 
The Moulting of the Second or Juvenile Down . . .115 
The Moulting of the Immature and Adult Plumage . . . . . .117 
Duration of the Moulting Period . . - . . . . .118 
Ordinary Behaviour of King Penguins in Captivity . . . . . . . 122 
Behaviour of King Penguins before and during the Moulting Period . . . . .126 
Daily Notes made during the Moulting Period of a King Penguin . . . . . .127 
Note on the Moulting of three King Penguins in 1916 . . . . . . . 130 
Explanation of Plates . . . . . . . . . . .131 
The Moulting of the Second or Juvenile Down. 
As the King Penguin chick grows, the down tassels forming the prepennse increase 
in length until they measure from 50 to 75 mm. (2 to 3 inches) over the greater 
part of the body. Some of the barbs of the juvenile down carry for some time natal 
down barbs on their tips, and the inner ends of all the barbs forming the tassels are 
eventually found to be continuous with barbs of either the main shaft or the after- 
shaft of the developing true feathers. How long the down coat is worn by any 
given King Penguin is not definitely known — it is said that King Penguins may not 
moult the prepennse until they are nearly a year old ; neither is it known at what 
time of the year the majority of the King Penguins living under natural condi- 
tions in South Georgia shed their prepennse, or how long the moulting process 
usually lasts. 
From the information collected by Mr Murphy* and others, it is evident that 
the breeding season lasts as long as the Antarctic summer, and that throughout the 
summer there are moulting as well as breeding birds on the rookeries. If some birds 
are hatched in January and others in March, and if the prepennse are worn as a rule 
for about ten months, and got rid of in from ten to twenty days, one would expect to 
find many birds in the act of shedding their down during the Antarctic midsummer. 
The view that a coat of true feathers is acquired, and that the young are ready to 
take to the water before the Antarctic summer comes to an end, is confirmed by 
Murphy, who came across a number of King Penguins in the act of shedding their 
down coats on December 16, 1913 — these birds were full-grown, but still had tell- 
tale ragged patches of long down attached to their newly acquired true feathers. 
From young penguins living in captivity nothing very definite has yet been 
* Murphy, Science Bulletin, The Museum of the Brooklyn Institute of Arts' and Sciences, vol. ii, No. 5, p. 109. 
TRANS. ROY. SOC. EDIN., VOL. LII, PART I (NO. 5). 19 
