NUTRITION AND FEEDING MECHANISMS 



245 



ducks, the majority of gulls and terns; offshore species which range out to 

 the continental edge, e.g. gannets, auks, certain gulls; and pelagic species, 

 notably the tubinares (petrels, shearwaters, albatrosses) and penguins. 

 The food of the various species is determined by availability in the regions 

 frequented but each species has its own inherent feeding habits (Fig. 5.30). 

 Along shores the sandpipers and plovers feed on small Crustacea, in- 

 sects, worms and molluscs secured at the surface, by turning over stones or 

 weed or by probing into the ground. Curlews, willets and phalaropes have 



<9> (M 



Fig. 5.30. Heads of some Marine Birds 



(«) Oyster catcher Haematopus; (b) sooty tern Sterna fuscata; (c) brown pelican Pele- 

 canus occidentalis; (d) cormorant Phalacrocorax; (e) gannet Sulci bassana, (/) puffin, 

 Fratercula; (g) dovekie Alle alle; (h) razor-billed auk Alca torda. 



long thin bills which serve for probing in sand and mud. Oyster-catchers 

 {Haematopus) and turnstones (Arenarid) use their chisel-like bills for 

 jabbing shellfish or knocking limpets off rocks. 



In high latitudes of the southern hemisphere are found peculiar littoral 

 birds known as sheath-bills (Chionididae). The sheath-bill is an omnivor- 

 ous scavenger but also feeds in the inter-tidal zone on small fishes and 

 invertebrates. Another antarctic scavenger is the giant fulmar (Macro- 

 nectes giganteus). At sea it feeds on Crustacea and squid, but it spends much 

 time on land, where it eats offal and attacks other birds. 



Gulls have varied feeding habits. They gather shellfish, worms, crusta- 



