Host density predicts presence of cuckoo parasitism in reed warblers

Abstract

In some hosts of avian brood parasites, several populations apparently escape parasitism, while others are parasitized. Many migratory specialist brood parasites like common cuckoos, Cuculus canorus , experience a short breeding season, and in order to maintain local parasite populations host densities should be sufficiently high to allow efficient nest search. However, no studies have investigated the possible effect of host density on presence of cuckoo parasitism among populations of a single host species. Here, we investigated possible predictors of common cuckoo parasitism in 16 populations of reed warblers, Acrocephalus scirpaceus , across Europe. In more detail, we quantified the effect of host density, number of host breeding pairs, habitat type, mean distance to nearest cuckoo vantage point, predation rate and latitude on the presence of cuckoo parasitism while controlling for geographical distance among study populations. Host density was a powerful predictor of parasitism. We also found a less pronounced effect of habitat type on occurrence of parasitism, while the other variables did not explain why cuckoos utilize some reed warbler populations and not others. This is the first study focusing on patterns of common cuckoo-host interactions within a specific host species on a large geographic scale. The results indicate that if host density is below a specific threshold, cuckoo parasitism is absent regardless of the state of other potentially confounding variables.Most studies on avian brood parasitism have focused on single populations (Rothstein and Robinson 1998, Davies 2000). However, spatially heterogeneous environments are likely to influence both distribution of populations and their dynamics (Hanski 1999). Therefore, spatial differentiation of various populations of hosts and parasites (metapopulation scenario) may lead to local adaptations and spatial variation in coevolution of parasites and their hosts (Thompson 1994(Thompson , 2005. The investigation of host Áparasite dynamics in a metapopulation context has so far mainly been applied to plants and their pathogens (reviewed by Kaltz and

Discordancy or template-based recognition? Dissecting the cognitive basis of the rejection of foreign eggs in hosts of avian brood parasites

“…Many hosts have evolved strategies to reduce the costs of parasitism Takasu et al, 1998;Schulze-Hagen et al, 2009). One of the most prevalent adaptations against brood parasitism is egg rejection, showing individual , sex-related (Palomino et al, 1998;Soler et al, 2002;Honza et al, 2007b;Pozgayová et al, 2009), population (Lindholm, 1999;Stokke et al, 2007a) and species-specific variability Davies and Brooke, 1989;Moksnes et al, 1991;Røskaft et al, 2002;Servedio and Hauber, 2006). Eggshell characteristics (e.g.…”

Egg phenotype matching by cuckoos in relation to discrimination by hosts and climatic conditions

“…We studied cuckoo -host egg matching in 2003 and 2004 in all reed warbler populations found to be parasitized by cuckoos (n ¼ 7) in a recent meta-populational study on reed warbler -cuckoo interactions (see [37] for further details; figure 1). In each population, we systematically searched for reed warbler nests during three weeks of the breeding season of the host.…”

“…Therefore, we here relied on daily temperature and precipitation from 1 May to 30 June as local weather variables used to identify spatial patterns in cuckoo and reed warbler egg phenotypes mediated by environmental conditions. We selected this period because it was the period when all sampled clutches were laid [30,37]. Daily climatic data on temperature and precipitation in 2003 for the studied reed warbler populations were obtained from the European Climate Assessment and Dataset (ECA&D) project (http://eca.…”

“…Populations are connected by gene flow and migration [33,34], and show a pattern of genetic isolation by distance [35]. Previous studies have found that both cuckoo parasitism rate and rejection of cuckoo eggs by reed warblers vary spatially [24,36,37]. Also, rapid temporal increase in cuckoo egg matching in a recently parasitized reed warbler population has been observed [38], suggesting that there is scope for evolutionary response of the parasite across a large geographical scale.…”

Factors influencing host nest use by the brood parasitic Asian Koel (Eudynamys scolopacea)

“…Reproductive success in many avian brood parasites is strongly influenced by the number and quality of potential hosts present (e.g., Stokke et al 2007), and the parasites are often detrimental to host fitness (Davies 2000). To optimize fitness, there should be strong selection on parasites for efficient and successful nest searching behavior (Rothstein 1990;Ortega 1998).…”