THE MANX SHEARWATER. 423 



Nestling. 1st down. — Upper-parts varying mouse-brown to soft 

 grey-brown ; chin, throat and broad band down centre of breast 

 dividing and going down each side of belly to vent greyish-white ; 

 middle of belly and rest of under-parts grey -brown. Down soft 

 and long, covering bird very closely, short on lores, round eyes and 

 on chin. 



2nd down. — Like first but slightly darker, about same length 

 but slightly closer structure. Growth of 2nd down is almost 

 continuous with first and division of the two sometimes not very 

 clearly marked. 2nd down is succeeded by feathers, growth being 

 continuous and by time feathers grow most of 1st down has worn 

 off tips of 2nd down. 



Juvenile. Male and female. — Plumage immediately succeeding 

 2nd nestling down is like adult. 



Measurements and structure. — £ wing 225-244 mm., tail 74-82, 

 tarsus 42-47, middle toe with claw 47-53, bill from feathers 32-39 

 (14 British measured). $ wing 225-240, bill 33-36. Primaries : 

 1st minute, pointed and concealed by primary- coverts, 2nd longest, 

 3rd 2-5 mm. shorter, or occasionally as long, 4th 9—16 shorter, 

 5th 24-33 shorter, 6th 40-50 shorter ; outer web of outer (2nd) 

 primary considerably narrower than in rest. Outer secondaries 

 about as long as 10th and inner as 8th primaries. Tail rounded, 

 12 feathers, tips rather sharply rounded. Under tail -coverts nearly 

 as long as tail-feathers. Tarsus much compressed. Three toes 

 long, slender, and fully webbed, hind toe minute and free ; claws 

 fairly sharp and somewhat arched. Bill slender, tip of both man- 

 dibles compressed and sharply decurved, base broad and not 

 greatly elevated by parallel tubular nostrils, apertures of which 

 are oval and open at an angle inclined upwards and forwards. 

 Nostril tubes separated by ridge of culmen ; in nestling slit-like 

 on each side of culmen with only slight indication of tube. 



Soft parts. — Bill, leaden-black, cutting edge greenish, base 

 bluish -grey ; legs and feet pink-flesh, hinder edge and outer toe 

 brown-black, webs grey-blue and ochreous, claws brown-black ; 

 iris black. 



Characters and allied' forms. — For distinctions of P. p. maure- 

 tanicus see under that form. P. p. yelkouan (Mediterranean from 

 Corsica eastwards) is intermediate between P. p. puffinus and 

 P. p. mauretanicus, being rather browner on upper -parts than former, 

 flanks more or less sooty-brown, axillaries with longer brown tips 

 and under tail-coverts more brown than in P. p. puffinus. Black 

 upper-parts, pure white under-parts and size distinguish Manx 

 from other British Shearwaters. 



Field -characters. — Sometimes seen at rest on the water, but comes 

 under notice oftenest as it careers over surface of sea. A few rapid 

 beats alternate with periods of sailing with long narrow wings 

 quite rigid, dead black of back in view at one moment, pure white 



