Brood parasitism: a good strategy in our changing world?

Abstract

The original life-history strategy of brood-parasitic birds has been the focus of a large number of studies in ecology and evolution. Whether species adopting such a strategy differ in their response to global changes remains, however, unknown. Both the absence of investment in parental care and the capacity to spread nesting failure by laying eggs in several nests might help brood parasites in dealing with environmental changes. Alternatively, brood parasites might cumulate the negative effects of environmental changes on their own environment and on their hosts' environment. Here, I tested whether brood parasites' extinction risk and population trend differed from those of species with parental care. Focusing on the five bird families containing brood parasite species, I show that brood parasites are less at risk of extinction, and have a more stable population trend than species with parental care. In addition, I found that brood parasites with a higher host diversity were more likely to be increasing than those with fewer hosts. The bet-hedging strategy of brood parasites, by allowing them to spread nesting failure risks associated with environmental changes, is likely to help them resist current global changes.

Keywords: International Union for Conservation of Nature Red List; bet-hedging; global changes; host generalism.

Figure 1.

Distribution of brood parasites and species with parental care among extinction risk categories. Threatened species (critical, endangered, vulnerable and near threatened) were grouped into a single category. Species from the five families containing obligate brood parasites are included.

Figure 2.

Distribution of brood parasites and species with parental care among population trend categories. Species from the five families containing obligate brood parasites are included.

Figure 3.

Mean host diversity (residuals of a quasi-Poisson regression of host number versus research effort) of species within each population trend category (mean ± s.e.).