干旱区生态环境知识资源中心

Costs of conspecific brood parasitism (CBP) are expected to be influenced by a species’ life history traits. Precocial birds lay large clutches, and clutches that have been enlarged by CBP can affect host fitness through a longer incubation period, displaced eggs, and lower hatching success. We examined costs and response to CBP by hosts in a population of colonial red-breasted mergansers (Mergus serrator; n=400 nests over 8years) within which 29% of parasitized clutches were enlarged considerably (15 eggs). Length of the incubation period did not increase with clutch size. The mean number of eggs displaced from a parasitized nest during incubation (2.8) was 2xgreater than at an unparasitized nest (1.4). Hatching success declined by 2% for each additional egg in the nest. Thus, for a nest with15 eggs, one or more fewer host eggs hatch relative to an unparasitized nest with the same number of host eggs, assuming equal probability of success for all eggs. Hosts were 40% more likely to desert nests receiving 2 or 6 experimental eggs relative to unparasitized control nests, although it is unknown whether hens deserting a nest renested elsewhere. Our study indicates that costs of CBP to hosts during nesting may be limited to those red-breasted mergansers incubating the largest clutches (15 eggs), and it raises questions about the adaptive significance of deserting a parasitized clutch.