The Relation of Breeding Schedule and Clutch Size to Food Supply in the Rufous-Sided Towhee

Abstract

Food is important as an ultimate factor in the timing of breeding (Moreau 1950, Lack 1954, 1966, 1968) and in the evolution of clutch size (Lack 1954, 1966, 1968, Cody 1966, 1971, Klomp 1970, von Haartman 1971) in birds. Although early studies emphasized the significance of food for dependent young (see Lack 1954), it now appears that the food available to the laying female may have a proximate effect as well on the date of first egg deposition and on clutch size, at least in some species (Pitelka et al. 1955, Mebs 1964, Perrins 1965, 1970, Cody 1966: Table 1, Lack 1966, Bengtson 1971, Moss et al. 1971). In this paper, I examine the relation of breeding schedule and clutch size to food in populations of Rufous-sided Towhees (Pipilo erythrophthalmus) inhabiting two different habitats along the northeastern Atlantic seaboard.