502 PROCEEDINGS OF THE NATIONAL MUSEUM. "^oi.. m. 



is^made for the varying proportions of moisture in the total, it will 

 be found that the proportion of nitrogen to solid matter is almost 

 exactly the same in the pure guano as in the two Cerro Azul samples. 

 From the most elementary principles of mammalian physiology 

 it is, of course, to be inferred that the nitrates would be absent from 

 the guano on account of being excreted with the urine and in a form 

 subject to loss both by evaporation and seepage. From all observa- 

 tions it is safe to say that the sea lions should not be credited with 

 any significant part in the formation of the guano deposits, both 

 on account of the small amount deposited by them in secure places 

 and because of the low nitrogen value of the guano. 



THE SEA LION AS ENEMY AND COMPETITOR OF THE BIRDS. 



The suggestion that the sea lions, as great consumers of fish, have 

 caused a serious diminution in the food supply, and consequently in 

 the abundance of birds, may be briefly dismissed. Sea lions are, of 

 course, competitors of the birds in the search for food, but the sea 

 lions and birds have existed together for untold ages, and there is 

 entirely wanting any evidence of suffering on the part of the birds 

 for want of food. On the contrary, I was invariably impressed with 

 the comparatively brief portion of the day occupied by the cormorants 

 and pelicans in the search of food, and the correspondingly consid- 

 erable proportion of the time which, they spend upon the islands. 

 There is every reason to believe that these birds are not nearly up to 

 the maximum number which might exist upon the normal food 

 supply, and the deficiency is without any question attributable to 

 the molestation of the rookeries during the past 60 years. 



That the sea lions will destroy birds at times is indisputable. 

 Many persons with long experience on the islands mentioned having 

 seen the sea lions eat the birds or tear them open for the fish con- 

 tained within. Many of these observations are perhaps made under 

 abnormal circumstances when helpless birds are forced into the water. 

 However, I had the rare opportunity to witness the killing of a pelican 

 by a sea lion, and the incident is worthy of description. It should be 

 mentioned that this was near an abandoned island, so that there was 

 no known unusual circumstance to demoralize the bird. 



When first seen the lobo had taken the bird apparently by the legs. 

 He dragged it about a little and then by an arched dive carried his 

 captive completely out of view under the water. After a few seconds 

 they were up again. This action was repeated several times, the lobo 

 evidently endeavoring to get a good hold with his jaws on the belly 

 of the bird, protected by its very thick covering of feathers. At first 

 the pelican made so little struggle that I should have thought it dead, 

 but that the neck was held quite erect. It seemed thoroughly 

 demoralized, but, after the third dive, began to fight the lobo with 



