540 PROCELLARIIDAG 
on December 5th, 1905 (Ralfe, ‘ Zoologist,’ 1906, p. 194). 
A fourth picked up in co. Fermanagh on November 28th, 
1905 (C. Langham, ‘ Irish Naturalist,’ 1906, p. 45). 
In its general habits this Petrel resembles the last 
species ; when not breeding it leads a wandering, pelagic 
life, flitting over the tossing billows and following in the 
wake of a vessel for many miles. Single birds or small 
parties are usually seen. 
Flight——Except for its forked tail this Petrel is not 
easily distinguished on the wing from the last species. The 
flight of the two birds over the ocean is practically similar. 
Mr. A. Williams observed six on the wing near Clontarf 
estuary, close to Dublin. He describes how they hovered 
with their heads to the wind, tipping the water with their 
tiny black feet (‘ Zoologist,’ 1882, p. 18). | Mr. Ussher men- 
tions two that were seen, also flying against the wind for 
several hours, along the margin of a lake in Westmeath. 
Voice.—The note resembles the syllables pewr-wit, 
pewr-wit (Saunders). 
Food.—Refuse, chiefly of an oily character, together with 
cuttle-fish, small crabs, and shell-fish, constitute the diet. 
The stomach generally contains a rather transparent oil. 
Nest.—In the breeding-season, in May, the Forked-tail 
Petrel exhibits the same gregarious propensities as the last 
species. It is fond of hiding in subterranean passages, and 
in daylight will suffer an intruder to pull it out of a burrow 
(its usual nesting-site), rather than take flight. It some- 
times nests in rock-crevices, near the summit of precipitous 
islands. 
The nest is a hollow, scantily lined with withered grass, 
or, in some cases, a naked depression in the soil. The 
single egg is white in colour, sometimes finely marked with 
reddish-brown specks forming a zone near the larger end. 
Incubation commences early in June; an oily smell per- 
vades the breeding-haunts. 
This Petrel has been found nesting in several of the 
Island Groups off the western sea-board of Scotland, in- 
cluding St. Kilda’ (where it has extensive colonies), North 
Rona and several Islands of the Outer Hebrides. 
Mr. Ussher, in his work on the ‘ Birds of Ireland,’ gives 
1In Boreray it nests in the ‘cleets’ or little turf houses of the 
natives among the sods of dry turf (Harvie-Brown, Ann. Scot. Nat. 
Hist., 1903, p. 17). 
