Biology subjects

Delhey, K.

Publications and source records attributed to Delhey, K..

4 recordsLinked to original sources

bioRxiv2021

Cooperative breeding and the emergence of multilevel societies in birds

Multilevel societies (MLSs), where social levels are hierarchically nested within each other, are considered one of the most complex forms of animal societies. Although thought to mainly occur in mammals, it is suggested that MLSs could be under-detected in birds. Here we propose that the emergence of MLSs could be common in cooperatively breeding birds, as both systems are favoured by similar ecological and social drivers. We first investigate this proposition by systematically comparing evidence for multilevel social structure in cooperative and non-cooperative birds in Australia and New Zealand, global hotspots for cooperative breeding. We then analyse non-breeding social networks of cooperatively breeding superb fairy-wrens (Malurus cyaneus) to reveal their structured multilevel society, with three hierarchical social levels that are stable across years. Our results confirm recent predictions that MLSs are likely to be widespread in birds and suggest that these societies could be particularly common in cooperatively breeding birds.

ecology↗

bioRxiv2020

Body size and climate as predictors of plumage colouration and sexual dichromatism in parrots

Psittaciformes (parrots, cockatoos and lorikeets) comprise one of the most colourful clades of birds. Their unique pigments and cavity nesting habits are two potential explanations for their colourful character. However, plumage colour varies substantially between parrot species and sometimes also between males and females of the same species. Here, we use comparative analyses to evaluate what factors correlate with colour elaboration, colour diversity and sexual dichromatism. Specifically, we test the association between different aspects of parrot colouration and (1) the intensity of sexual selection and social interactions, (2) variation along the slow-fast life-history continuum and (3) climatic variation. We show that larger species and species that live in warm environments display more elaborated colours, yet smaller species have higher levels of sexual dichromatism. Larger parrots tend to have darker and more blue and red colours. Parrots that live in humid environments are darker and redder, whilst species inhabiting warm regions have more blue plumage colours. In general, the variables we considered explain small to moderate amounts of variation in parrot colouration (up to 20%). Our data suggest that sexual selection may be acting more strongly on males in small, short-lived parrots leading to sexual dichromatism. More elaborate colouration in both males and females of the larger, long-lived species with slow tropical life-histories suggests that mutual mate choice and reduced selection for crypsis may be important in these species, as has been shown for passerines.

evolutionary biology↗

bioRxiv2019

REVEALING THE COLOURFUL SIDE OF BIRDS: SPATIAL DISTRIBUTION OF CONSPICUOUS PLUMAGE COLOURS ON THE BODY OF AUSTRALIAN BIRDS

In many species of birds, different body parts often display very different colours. This spatial distribution of coloured plumage patches may be determined by the balance between being cryptic to predators, and conspicuous to intended receivers. If this is the case, ventral and anterior body parts in birds-which are less visible to predators but more prominent to conspecifics- should present more conspicuous and sexually dichromatic plumage colours. Here I test these predictions using reflectance spectrometric measurements of standardised plumage patches across males and females for nearly an entire avifauna (Australian landbirds, N = 538 species). My data show that, as predicted, conspicuous colours are mainly located near the head, while the plumage of the back is the most cryptic. However, there is considerable variation across species, and this makes position on the body a relatively modest predictor of plumage elaboration (R2 = 0.15-0.19). One clear exception to this pattern is the conspicuous rump coloration. In many species, this patch can be concealed by wings, and therefore exposed only when necessary. In addition, conspicuous rump coloration could deflect or confuse predators in case of attack. Finally, patterns for sexual dichromatism were much weaker (R2 = 0.02), whereby wing and tail showed lower levels of dichromatism than the rest of the body.

evolutionary biology↗

bioRxiv2018

RECONCILING ECOGEOGRAPHICAL RULES: RAINFALL AND TEMPERATURE PREDICT GLOBAL COLOUR VARIATION IN THE LARGEST BIRD RADIATION

Ecogeographical rules that associate climate with organismal form and function can reveal patterns of climatic adaptation. Two rules link animal coloration with climate: Glogers rule (darker coloration where wet and warm), and Bogerts rule (darker coloration where cold). Whereas Glogers rule was proposed for endotherms, and Bogerts rule for ectotherms, both rules may apply more broadly, despite their seemingly opposing effects. Here we test this contradiction on a global scale across passerine birds. Consistent with Glogers rule, birds were darker in wetter areas and, following Bogerts rule, lighter where warm, although birds became lighter again at very low temperatures. Rainfall and temperature had antagonistic or additive effects depending on their pattern of covariation, and this predicted whether birds followed the rules. We integrate both rules into a general framework to explain heterogeneity in climatic effects on coloration, which has implications to understand patterns of diversification, climatic adaptation and climate change impacts.

evolutionary biology↗