Search results for "Avian brood parasitism"

Reed Warbler Hosts Do Not Fine-Tune Mobbing Defenses During the Breeding Season, Even When Cuckoos Are Rare

2021

Hosts of brood parasitic cuckoos often employ mobbing attacks to defend their nests and, when mobbing is costly, hosts are predicted to adjust their mobbing to match parasitism risk. While evidence exists for fine-tuned plasticity, it remains unclear why mobbing does not track larger seasonal changes in parasitism risk. Here we test a possible explanation from parental investment theory: parents should defend their current brood more intensively as the opportunity to replace it declines (re-nesting potential), and therefore “counteract” any apparent seasonal decline to match parasitism risk. We take advantage of mobbing experiments conducted at two sites where reed warblers (Acrocephalus sc…

Avian brood parasitism in Italy: Another perspective

2020

We present a quantitative analysis of the data reported in the only published review of parasitism frequency on hosts of Common Cuckoo Cuculus canorus in a Mediterranean area. We first eliminated a bias potentially introduced by the method by which data were recorded. Of the initial potential 70 species parasitized in Italy, only 44 were confirmed as host species, of which only 10 species had more than 10% of their total nests parasitized. We highlighted differential parasitism on host species according to geographic area, but the analysis suggested results were strongly biased because nest location was generally not reported and the number of records steeply decreased from North to South.

Avian brood parasitism in the new and old worlds

Evolutionary consequences of social transmission in avian brood parasitism systems

Obligate brood parasites lay all of their eggs in nests of other species, leaving the burden of parental care entirely to the hosts. As a consequence of being parasitized, hosts’ reproductive success is often reduced. This strategy has triggered a coevolutionary dynamic involving behavioural, physiological and morphological adaptations and counter-adaptations from the two players, whose conflicting functions are to successfully parasitize a nest, and prevent or reduce the negative effects of parasitism. In parasite systems studied in the New and Old worlds, warbler hosts exhibited different degrees of learning antiparasite defences from conspecifics. By quantifying strength and direction of…

Analysis of Prey Composition in Eurasian Reed Warblers' Acrocephalus scirpaceus Droppings at Four Breeding Sites in Italy

2022

Our aim was to investigate the among-populations diversity of prey composition in Eurasian Reed Warblers’ diets via their droppings, both to assess the ecological validity of this sampling method and to test whether the prey species most abundant in fecal samples were also the most present in the Italian study site. We collected fecal samples at four sites throughout Italy, for a total of 144 samples. Within reedbeds, the breeding habitat of the Eurasian Reed Warbler, we also collected arthropods by carrying out entomological sweepings at one of the study sites. Within the fecal samples, we identified dozens of prey species, belonging mainly to Araneae, Coleoptera, Diptera, Hymenoptera and …

Reed Warbler Hosts Do Not Fine-Tune Mobbing Defenses During the Breeding Season, Even When Cuckoos Are Rare

2021

Hosts of brood parasitic cuckoos often employ mobbing attacks to defend their nests and, when mobbing is costly, hosts are predicted to adjust their mobbing to match parasitism risk. While evidence exists for fine-tuned plasticity, it remains unclear why mobbing does not track larger seasonal changes in parasitism risk. Here we test a possible explanation from parental investment theory: parents should defend their current brood more intensively as the opportunity to replace it declines (re-nesting potential), and therefore “counteract” any apparent seasonal decline to match parasitism risk. We take advantage of mobbing experiments conducted at two sites where reed warblers (Acrocephalus sc…