THE BIRDS OF THE JUAN FERNANDEZ ISLANDS 13 
and may be taken without difficulty when sitting on the eggs. The breeding 
season is the end of January and the month of February. There appears to 
be only 100—200 specimens of this bird on the island.» (K. B.). 
By the non-burrowing habits this species differs from an oecological point 
of view from P¢. melanopus (v. solandrz), 
Pterodroma (Aestrelata) externa Salvin 
Masatierra: 1 ¢ 74/; 1917. 
Masafuera: 2 dd 15/2, 1.2 1%/e, 1 Y 75/2 1917, all adult; Downy chicks: 
I unsexed 1/3, 1 , a little larger, 8/2 1917. 
The measurements of these specimens, in the same order as enumerated 
above, are: 
o of o g 2 
WWI Soe er 307.5 316,5 323 298,5 309 mm. 
Culmen! .. 34.3 40 38,3 39,2 38,5 » 
The length of the middle toe with claw is 50—52, the length of the 
tarsus 39—4I mm. 
The chicks are pale slaty grey above and white underneath. Their down 
is very fluffy, especially on the upper side. White filoplumes are, as mentioned 
by Loomis, to be seen on the head of the males, but they are numerous only 
in one of the specimens collected '°/s. 
» Pterodroma externa is the commonest bird of Masafuera. The nests are 
found everywhere above 500 meters. It burrows and makes tunnels, which 
may attain a length of even three meters. The entrance is generally concealed 
among the ferns (Lophosoria), but may also be seen on open ground. The 
nest is not lined at all, but fragments of ferns are sometimes found within. 
Only one egg is laid. As far as I have been able to find out, the bird breeds 
only once a year. The eggs are pure white. With regard to the shape, two 
equally common types may be discerned, one resembling that of the domestic 
hen, the other that of the turkey.» 
»In daytime no Fardela is ever seen over the island, but in great numbers 
over the sea. At dusk they all come out of their burrows and fly in numbers 
over the island and along the shore, making a terrible noise.» 
»At Masatierra now and then some few birds of this kind were seen, but 
they soon returned.» (K. B,). 

' From forehead to tip of hook in a straight line. 
