The Researcher established field sites, logistics and local networks for examining the nest architecture of weavers and their interactions with Diederik cuckoo brood parasites. Initial field data was collected and analysed (see below for more details), including physical nest morphometrics, and data were extracted from calibrated and reliable imaging approaches. The Researcher also had online meetings with named collaborator Prof Stoddard in Princeton. Although the initial results of this work were suggestive of relationships existing between different nest characteristics measured from an individual nest, and between nest characteristics and the social environment, it was not possible to analyse the data further or to collect more data to follow up these promising lines of enquiry.
Before starting work on investigating the role of nest characteristics in contributing to defences against cuckoos, it was necessary for the Researcher to use the first year of work to conduct some preliminary investigations into the other factors that contribute to host defences against cuckoos. Part of this work was an invited review considering the adaptive value of cuckoo resemblance to hawks, the physiological responses it evokes in hosts and therefore the type of defences that are then mounted (York 2021, Frontiers in Ecology and Evolution).
A second part of this work involved some field experiments conducted in South Africa between October 2019 and March 2020 on diederik cuckoos their host, the southern red bishop. The sexes differ in Diederik cuckoos, with females bearing duller plumage than males and sporting a brown iris and eye-ring rather than the crimson equivalents displayed by the males. The experiments revealed that hosts were just as likely to mob a male cuckoo or a female cuckoo (or a control). Curiously, though, the incidence of egg-rejection was greater when a male cuckoo visited the nest than when a female cuckoo visited. The results suggest that, independent of any nest characteristics, the female's drabber appearance might be adaptive in eliciting weaker rejection defences by hosts than is seen in response to males (York 2024, Ecology and Evolution).
Meanwhile, background work on the breeding biology of weavers was brought fruition through the publication of three preprints/ papers. The first investigated the role of prolactin in regulating parental care and helping behaviour in white-browed sparrow weavers (Walker et al 2021 BioRxiv). The second considered how rainfall and social dominance contribute to telomere dynamics (Wood et al 2022 Molecular Ecology). The third paper examined the trade-off that exists between helping behaviour and dispersal in males and females (Capilla-Lasheras et al. 2024 PLoS Biology).
