FOOD ABUNDANCE AND PARENTAL CARE IN YELLOW WARBLERS (DENDROICA-PETECHIA)

Emlen and Oring (1977) suggested that monogamy in birds is maintained because of the need for strict biparental care. A corollary of their s uggestion is that paternal care should decrease under conditions of hi gh food abundance. An alternative is that paternal care would increase if males take advantage of the higher food abundance by trying to red uce the length of the nestling feeding period. We tested these two ide as using yellow warblers (Dendroica petechia) by providing some pairs with supplemental food, thereby reducing the importance of biparental care. However, the extra food did not decrease paternal effort, nor di d it increase it (Fig. 2). Early in the nestling period experimental f emales brooded more but visited their nestlings less than did control females, but later, when brooding times decreased, experimental female s fed their nestlings more than did control females (Fig. 3). There we re no significant differences in nestling survival(Fig. 5), but nestli ngs in the control treatment were larger and heavier up to 6 days old (Fig. 6). The main effect of supplemental food was on maternal, not pa ternal behaviour. Models of biparental care assume interdependence bet ween the parental effort of both parents. In this species, however, ma les and females provide for their brood independently from each other.