I04 ANIMAL ECOLOGY 



and sand-banks diWded one from another by shallo\^'s, 

 oozes, and back\vaters. At inten'als these natural sanctuaries 

 are so completely caq)eted ^^-ith water-fowl as to present an 

 appearance of being, as it were, ttssellutcd ^^ith li\-ing creatures, 

 and tliat over a space of perhaps half a niile and sometimes 

 more. These feathered armies are composed not only of ducks 

 and geese but also of tall cranes, herons » and storks, marshalled 

 rank beyond rank in sembLmce of squadrons of cavalr\'.'' 

 This amazingly rich bird-life has been photographed by 

 Bengt Berg,^'- and the reader may be referred to his book, the 

 illustrations of which \\i\\ show that the description given 

 above is not in tlie least exaggerated. 



5. It would be a mistake to imagine that such an abundance 

 of birds is only to be met \Wth in tropical regions. In the .\rctic, 

 where continuous daylight throughout the summer encourages 

 a rich hars-est of diatoms and other ph)-toplankton near the 

 surface of the sea, upon which is based an equally rich com- 

 munit}- of plankton animals, there are still to be found in some 

 places stupendous numbers of sea-fowl. Guillemots are 

 particularly abundant, for they breed in great colonies on the 

 sides of steep sea-cliifs, where their black and white costume 

 makes them ver\- conspicuous. The ^^Titer is thinking of one 

 clitf in particular on which the birds could be seen sitting 

 packed close together on even- ledge of rock up to a height of 

 a thousand feet or more. When a gun was tired a few odd 

 hundred thousand or million birds would tly oil in alarm, 

 without, however, noticeably affecting the nimibers still to be 

 seen on the cliff. The photograph in Plate VII (ti) \rill give 

 some idea of the number of birds ti\ing oil the clilT, and 

 therefore a remote idea of the number not fl>*ing olf. In the 

 photograph each streak of black represents not one bird, 

 but a small tiock of ten to thirt}'. The noise made by 

 these multitudinous egg-layers resembled that produced by 

 an expectant audience in a vast opera house, t\Nittering and 

 rustling its programmes. 



6. In the southern hemisphere the penguin rookeries 

 afford an example similar to that of the guillemots in the north ; 

 but the penguins spread out their colonies over the ground 



