Abstract
Avian nests present great variation in structure but, after excluding cavity nesters, probably the most obvious difference is that between open and domed nests. Some species lay their eggs in open structures, exposed to environmental variables, while other species build domed, enclosed nests with a roof, which are suggested to protect eggs and nestlings from weather conditions, high radiation levels, and predation. To date it is unclear which variables drove the evolution of different nest types. In this study, environmental and nest type information was extracted for continental Australian passerines, showing that species with open and closed nests are distributed in similar climates. However, species with open nests have larger ranges and are distributed in a wider variety of climatic conditions, suggesting open nests could be an evolutionary key innovation. This analysis was complemented with a detailed study of the evolution of particular nest traits in the largest Australasian avian radiation (Meliphagoidea), confirming that adult body size – but not environment – is an important factor in nest architecture, and larger species tend to build nests that are shallow and supported from underneath. Nest structure is a multidimensional trait that has probably evolved to match the phenotype of the nest owner, but that could also constrain or facilitate establishment in different environments.
Highlights
Bird nests have fascinated biologists for centuries due to the wide diversity of nest types, and many explanations have been proposed to explain such variation
The broad analysis on Australian passerines shows that principal components describing temperature or radiation cannot predict whether a species has a domed or an open nest (Table 1, Fig. 1a,b)
Contrary to what has been previously proposed[12,13], temperature across the range could not predict the type of nests in Australian passerines
Summary
Bird nests have fascinated biologists for centuries due to the wide diversity of nest types, and many explanations have been proposed to explain such variation. Www.nature.com/scientificreports might be so specialized (i.e. adapted to a relatively narrow set of environmental conditions) that this could result in restriction of the dispersal and distribution of the species. Australian avifauna is exposed to different climates, there is a high likelihood that all share relatively similar biotic conditions (e.g. are exposed to similar predators, brood parasites, and flora), at least compared to species outside the continent. This provides a more controlled environment for hypotheses testing[12,23]. Phylogenetic analyses suggest that passerines originated and radiated in Australasia, and Australia presents a large number of the passerine families of the world[24,25], which makes the present results relevant in a wider evolutionary context
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