SECT. 3] ORGANIC TRANSPORTATION OF MARINE SEDIMENTS 785 



Oldham (1930), who also mentioned the application of the same technique to 

 the opening of hermit crabs, turtles, and even walnuts by various birds. 

 According to Fitch, it is sometimes a little hazardous to walk on the causeway 

 at Mission Bay. near San Diego, or along the shore at Pebble Beach, California, 

 when gulls are preparing clam dinners. Accumulations of broken shells formed 

 in this manner are not uncommon (Andree, 1926, pp. 719, 730; Teichert and 

 Serventy, 1947). Many broken tubes of vermetid mollusks noted by the writer 

 atop a small island near Guaymas, Mexico, were probably so deposited. A 

 curious indirect role is played by woodpeckers through their habit of placing 

 pebbles in holes drilled in tree trunks when nuts are not available (Ritter, 1938); 

 the possible later floating away of the trees results in transportation of the 

 pebbles. 



An occurrence of a new species of mollusk in a guano deposit, as described by 

 Smith (1952), resulted from the swallowing of the mollusk by a fish which 

 was later caught and eaten by a cormorant which deposited the mollusk by 

 regurgitation or excretion in its nesting area. 



Living animals and plants may also be deposited unintentionally by birds 

 as contamination on dirty feet (Ladd, 1960), or stuck to feathers (Wiens, 1962). 

 Murphy (1936, p. 422) even mentioned the presence of barnacles growing on the 

 feet of a penguin presumably long at sea. B. C. Cotton described a Black Duck 

 from Australia on wiiose foot a 30-g mussel had closed; the bird had been seen 

 flying with its foot hanging and was shot. The same species of mussel withstood 

 six months' exposure in mud after a river flood; another specimen survived 231 

 days out of water followed by shipment to England (Cotton, in litf.). In other 

 instances birds have been trapped by large clams (Jones, 1959). 



Some sea birds move quantities of stones or mud in building their nests. 

 Penguins use pebbles and have been observed to walk a kilometer to get a 

 single nest pebble, often by robbing an untended nest (Murphy, 1936, pp. 373, 

 393, 394, 412, 447, 449). According to Limbaugh, noddy terns at Clipperton 

 Island have carried hundreds of tons of coral rubble and shell for courtship 

 and nesting materials onto the rocky surface around the lagoon. Albatrosses, 

 pelicans and boobys mostly use mud for their nests, carrying it from more or 

 less distant shore areas to places where such marine sediments would not 

 naturally occur. 



During migrations or other travels, birds probably transport sand, shells 

 and pebbles as far as thousands of kilometers, eventually depositing them by 

 regurgitation, excretion or death. The quantities of sediment so deposited, 

 however, are so small that they may escape notice. In at least one instance 

 Sayles (1931, p. 443) suggested a bird-borne source of quartz grains in the soils 

 of Bermuda; however, more recent work indicates that the quartz sand more 

 probably came from underlying igneous rocks. 



7. Invertebrates 



Worms, holothurians, mollusks, crustaceans and other invertebrates con- 

 tribute in varying degrees to sediment transport. Most important are the various 



