FOOD, FEEDING HABITS AND TERRITORY OF THE ROCK PIPIT ANTHUS SPINOLETTA.

Abstract

Summary. This paper describes the food and ecology of a few Rock Pipits, mainly in Cornwall in winter. Rock Pipits prefer exposed to sheltered coasts. Their average density in favourable habitats was ca. 8 pairs per mile of coast. Rock Pipits fed chiefly on the shore in winter and just inland in summer. Rock Pipits fed more intently in mid‐winter than in spring and autumn; and, at any one season, most intently when food was scarce. Also, they fed more intently in the afternoon than in the morning in mid‐winter (correlated with the long winter nights), and vice versa in spring and autumn. Whenever food was scarce they fed hard all day. There were four common littoral foods in winter:the periwinkle Littorina neritoides , chironomid midge larvae, dipteran larvae ( Coelopa spp.), and isopods ( Idotea spp.). Amphipod hoppers (Talitridae) were sometimes an important food in late summer. The availability of these foods and the predation of the Rock Pipit upon them are described; rates of feeding and defaecation were measured. The total food consumption of one Rock Pipit was estimated for a number of days in December, 1950 and 1951. The dry weight of food eaten daily averaged ca. 26 gms. when periwinkles, and ca. 12‐5 gms. when chironomid larvae were the main food. The dry weights of organic material consumed daily were ca. 6 gms. (calorific value 30 Calories) in December 1950 and ca. 4 gms. in December 1951. When periwinkles were the main food the bird digested only 40% of the organic intake; hence its energy intake was ca. 12 Cals. daily. These results are compared with similar data for three other bird species. No other bird species seriously competed with the Rock Pipit for food. Intra‐ and inter‐specific fighting (chiefly for food), and the Rock Pipit's response to predators are described. Rock Pipits are intensely territorial; they defend individual territories in winter. The possible functions of territory are discussed:winter territories are primarily concerned with food. Conclusions: (i) since winter territories were just, but only just, big enough to provide sufficient food, their size was probably determined by their food resources; (ii) since Rock Pipits were sometimes apparently short of food and competed for it in winter, food shortage could limit their density.