Rapid change in host use of the common cuckoo Cuculus canorus linked to climate change

Abstract

Parasites require synchrony with their hosts so if host timing changes with climate change, some parasites may decline and eventually go extinct. Residents and short-distance migrant hosts of the brood parasitic common cuckoo, Cuculus canorus, have advanced their phenology in response to climate change more than long-distance migrants, including the cuckoo itself. Because different parts of Europe show different degrees of climate change, we predicted that use of residents or short-distance migrants as hosts should have declined in areas with greater increase in spring temperature. Comparing relative frequency of parasitism of the two host categories in 23 European countries before and after 1990, when spring temperatures in many areas had started to increase, we found that relative parasitism of residents and short-distance migrants decreased. This change in host use was positively related to increase in spring temperature, consistent with the prediction that relative change in phenology for different migrant classes drives host-use patterns. These findings are consistent with the hypothesis that climate change affects the relative abundance of different host races of the common cuckoo.

Figure 1.

(a) Relative parasitism rates of resident and short-distance migratory birds during 1990–2009 in relation to annual change in spring temperature (°C yr⁻¹) during 1990–2009. The line is drawn according to the best-fit binomial model controlling for relative parasitism rates before 1990 (see §3). (b) Change in relative parasitism rate of resident and short-distance migratory hosts in different European countries (frequency in 1990–2009 minus frequency before 1990) in relation to annual change in spring temperature during 1990–2009 (°C yr⁻¹). The line is drawn based on the parameters of a linear regression weighted by the number of cases of parasitism after 1990 in each country and is shown to illustrate the negative relationship. See text for the appropriate binomial general linear model analysis. In both panels, the size of the symbols corresponds to the number of cases of parasitism reported during 1990–2009. Each circle represents a different European country in the two panels, and the size of circles reflects sample size as indicated at the top of the figure.