THE BIRDS OF THE JUAN FERNANDEZ ISLANDS 1 3 



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 Pt. melanopus (v. solandri). 



Pterodroma (Aestrelata) externa Salvin 



Masatierra: i $ ^*/i 191 7. 



Masafiiera: 2 cTcT ^^/a, i ? ^^2, i ? ^^2 IQI?. all adult; Downy chicks: 

 I unsexed Va, i ?, a little larger, ^^2 1917. 



The measurements of these specimens, in the same order as enumerated 

 above, are: 



cf cf cT* ? $ 



Wing .... 307,5 316,5 323 298,5 309 mm. 



Culmen^ . . 34,3 40 38,3 39.= 38,5 » 



The length of the middle toe with claw is 50—52, the length of the 

 tarsus 39—41 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 '^/2. 



y> Pterodrojna 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. 



