SEA-BIRD NUMBERS AND MAN I O3 



a crop of fat young can be taken most easily just before the young fly 

 or swim away from the colony. Furthermore it seems that it is safe 

 to take up to half as many young as there are nests in the colony. 

 Of course, this concerns established colonies of great size whose origins 

 are lost in the depths of history, and it is possible that a new colony 

 just starting up, or a colony struggling for existence at the edge of a 

 species' range, cannot stand this kind of human predation. More- 

 over, there are certain acts which can be dangerous to the population, 

 such as the taking of eggs from species like the fulmar, which do not 

 lay replacements. With these reservations, it seems that man can 

 exploit a community of sea-birds without killing the geese that lay 

 the golden eggs, provided that he restrains his greed and takes less 

 than half that which it would be physically possible for him to take. 

 He may indeed one day need to consider, more seriously than at 

 present, the scientific exploitation of sea-birds for food. The figures 

 we have quoted above may then be not without value for fixing the 

 annual crop which can be gathered without depleting the colonies. 



* * ♦ 



Man can also, and does, affect the population of sea-birds in ways 

 other than by predation — for instance, by building on, or otherwise 

 altering, sea-birds' breeding sites and by putting waste matter into 

 the sea. Fortunately for sea-birds man has not much use for cliffs, 

 except to put lighthouses on, and as objects of admiration and amenity. 

 Occasionally man quarries a cliff or builds air raid shelters in it, or 

 uses it for target practice. But on the whole his exploitation of a cliffy 

 coast is not usually such as to drive away the sea-birds which nest upon 

 it. However, not all sea-birds nest on cliffs, and those which nest on 

 beaches and marshes, most particularly the terns, have suffered con- 

 siderably from shortage of nesting sites, due to man's activities in 

 draining marshes for agricultural purposes and in building houses, 

 expanding and developing seaside resorts and in the erection of aero- 

 dromes and bombing and artillery ranges. However, we must readily 

 admit that not all coastal aerodromes and bombing ranges have 

 driven the sea-birds away. Sometimes they have driven humans 

 away and increased the numbers of the local nesting sea-birds! 



Perhaps of all our British sea-birds the little tern suffers most from 

 human building. The chain of seaside cottages and concrete bungalows 

 that now strings along the back of every likely beach in England, and 

 many in Wales and Scotland, occupies each year yet more of the gravel 

 and sandy stretches occupied by the little terns. This is unfortunately 



