THE ANIMAL LIFE OF THE GROUP. 313 



half miles lon.u' ])y one and a liall' ln-oad, and is abdut fi»i-t\' l'ci'1 ahovc the sea 

 at the highest i)()iiit. In form, it i'eseml)les a great oval platter, and dislidike, 

 it holds a slialiow salt-Avatei- lake tliat varies in size to correspond witli llie 

 amount of rain that falls on the island. There seems to be abundant geologic 

 evidence to ]ii'ove that the island was at one time a closed coral reef or an 

 atoll that in the remote past was elevated above the surface of the sea. Thu.s, 

 the coral stone foundation was formed around the salt lake thai the sea and 

 the wind have since made over into a sand island. 



The low sand rim that surrounds the lake and forms the island i)ropcr, 

 slopes gently toward the sea without, and the lake within. On this double 

 beach that is half or three-quarters of a mile in width, a few vai'ietics of hardy 

 beach plants have established thems<'lves. Besides helping to hold Ihc sand in 

 place with their roots, these jilants have added the last touch necessary to 

 form an ideal home for this monster l)ird colony. 



This sand ring in tln' midst of the ocean is the regular home of more than 

 twenty species of birds, five of wdiich are found nowhere else in the world. I 

 have estimated from personal observation and data gathered f(U' tlic pui-pose 

 that more than ten million birds formerly visited Laysan Island each year. In 

 addition to the rather large list of regular residents that form the bulk of the 

 inhabitants, the island has a goodly number of species that visit it each 

 winter, including such birds as tattler, i)lover. curlew, turnstone, canvas-back, 

 shoveler, and a eleven or more occasional or accidental w'anderers, making a 

 total of at least three dozen species of birds that are known to visit this mere 

 speck of dry sand. 



Naturally, the struggle for existence, often for mere nest-room, is intense. 

 The air, the vegetation, the earth — all literallx' swarm with bird life. Almost 

 every inch of land down to the water's edge is occupied. In their home life 

 this concourse may be likened to the inhabitants of a great city. Not finding 

 room enough for all to live on the ground, they have turned the island into a 

 great apartment house, several flats in height. Nor are all the ilats above 

 ground. Some of the petrels, for example, dig holes live or six feet deep and 

 in them live thousands and thousands of night-flying birds that rear thcii- 

 >()ung. as it were, in the deeper sul)-basement of the colon\'. Another species tligs 

 l)ut two or three feet deep in the sand, and in this way occupies the entire sid)- 

 basement flat, without fear of molestation by the neighbors, above oi- below. 



The basement is inhabited by the wedge-tailed shearwatei-. It has chosen 

 this part of the island as a home, and the burrows that the\- make ai'c in count- 

 less thousands and of such size that a person walking across the island must 

 be careful where he steps, lest in an unguarded moment he caves in the roof 

 of a burrow and drops hip-deep into it. 



The surface of the ground, to continue our comparison, is the most valu- 

 able and hence the most densely-populated part of this wonderful bird city. 

 Under the bu.shes, in the roots of the grass, in th.- open spaces about the bunch- 

 grass, along the shore of the lake, or on the sv;\ slope, a dozen species find thi> 



21 



