Breeding success and brood parasitism affect return rate and dispersal distances in the great reed warbler
Abstract
Returning to a breeding site and decision where to breed belong to the key life-history traits, especially in migratory birds. Yet, we still lack knowledge about the drivers of adult return rates and breeding dispersal distances in populations under pressure of brood parasitism.
We explored these issues in a trans-Saharan migratory passerine, the great reed warbler (Acrocephalus arundinaceus), in a population parasitized by the common cuckoo (Cuculus canorus)-an evicting brood parasite. In 2008-2012, a total of 563 great reed warblers were colour-marked and 185 of them were re-encountered 303 times in a year following their breeding at a fishpond area in the Czech Republic.
We tested how brood parasitism and host breeding parameters in 1 year affect host return rate and dispersal distances in a following year. Return rate was lower in females fledging a cuckoo and in both sexes that failed to produce any offspring than in birds that fledged own chicks in the preceding year.
Individual brood parasitism had a negative effect on the probability of female returning, but this relationship disappeared when excluding females fledging cuckoos. Although return rates did not differ between females that rejected and those that accepted cuckoo eggs, rejecter females dispersed less than acceptors.
We conclude that brood parasitism and fostering the parasite might be negatively related to host female survival. The other breeding conditions might rather be related to the decision where to breed in the future.
Establishing new long-term studies monitoring parasitized populations might open up avenues for future research.