Intra-pair Cooperation, Fledgling Care, and Renesting by Northern Mockingbirds (Mimus polyglottos)


Dept. of Ecology, Ethology, and Evolution, 505 Morrill Hall, University of Illinois, Urbana, Illinois 61801, USA

Dept. of Biology, University of Dayton, 300 College Park, Dayton, Ohio 45469, USA. Reprint requests to be sent to RB


Male and female northern mockingbirds (Mimus polyglottos) cooperated in dividing labor between care of fledglings and renesting. This study during two breeding seasons demonstrated a temporal division of labor in this multi-brooded passerine. Both parents fed newly fledged young. One to four days after young fledged, males reduced feeding rates and began nest-building. Males delayed initiation of nest construction in proportion to the number of fledglings present. During nest-building, females provided more food to fledglings. Mates then switched roles. Females finished building nests, laid the next clutches, and began incubation; males fed fledglings until they were independent. Within pairs, males fed fledglings more than did females in one of two years. Both sexes defended fledglings against potential predators, although males provided stronger and more frequent defense. This is the first detailed description of a monogamous passerine that clearly demonstrates lack of brood division while renesting. Division of broods is largely precluded by the temporal division of labor, a behavioral mechanism increasing the probability of renesting. Attempts at renesting, in turn, are favored by a high level of nest predation in this population.