THE PELICANS 213 



The ability to fly well would seem to be important for the survival 

 of juveniles of a species with non-waterproof plumage, at least in 

 stormy northern latitudes where a heavy surf might make a landing 

 from the sea hazardous. (But. in the calm equatorial waters of the 

 Galapagos Islands there is a flightless species of cormorant; its life 

 history otherwise resembles that of other cormorants.) Thus young 

 cormorants can escape equinoctial gales by flying to the shelter of the 

 rocks, for they would drown if they could not. At what age the brown- 

 black plumaged Phalacrocorax species breed is not known. It is rare, 

 but not unknown, to see a gannet mated and with tgg or chick while 

 still carrying signs of immature plumage. It is not until the third 

 summer and fourth winter (that is, when it is three years old) that 

 the head and neck of the gannet are quite white, but the golden tinge 

 is almost absent; the rest of the plumage is like that of the fully adult, but 

 some of the wing feathers are still black (the secondaries are black with 

 some white), and the outer tail feathers are white and the inner ones dark. 

 The bird is in adult plumage when it is between four and five years old. 



The vital statistics of sea-birds have ever been a puzzle to orni- 

 thologists. The northern gannet, laying one ^gg, and today subject 

 to hardly any persecution by man, thrives and is increasing. The 

 cormorants lay between two and five or more eggs, are very heavily 

 persecuted and shot, chiefly by fishermen who resent their depredations, 

 but yet numerically they remain scarcely changed from year to year. 

 Out of many hundreds of cormorants ringed in the British Isles more 

 than 50 per cent have been shot, caught in nets, or otherwise killed 

 after five years; while their breeding colonies are frequently raided 

 by fishermen who destroy the young birds. It is therefore obvious that 

 in order to keep their number even stationary, the cormorant must be 

 a fairly long-lived species. In captivity it will live about lo or 12 

 years. David Stuart (1948) finds that the expectation of life on i 

 March (following the year of its birth) of the young cormorant (born 

 and ringed in a colony of 200-220 pairs at Mochrum, Wigtownshire, 

 Scotland) is only 2.2 years; which he finds makes it impossible for 

 the cormorant to maintain its numbers (on paper) as it has done in 

 fact, at Mochrum, for at least 80 years. But it should be remembered 

 that aluminium leg-rings wear and drop off' the legs of sea-birds after 

 a few years; the data accumulated by ringing can only be a guide to 

 the vital statistics. Among some birds (e.g. Manx shearwater) which 

 nest year after year in accessible sites, it is possible to obtain greater 

 accuracy by frequently renewing the rings of individuals under study. 



