Global drivers of variation in cup nest size in passerine birds

Abstract

1. The size of a bird's nest can play a key role in ensuring reproductive success and is determined by a variety of factors. The primary function of the nest is to protect offspring from the environment and predators. Field studies in a number of passerine species have indicated that higher-latitude populations in colder habitats build larger nests with thicker walls compared to lower-latitude populations, but that these larger nests are more vulnerable to predation. Increases in nest size can also be driven by sexual selection, as nest size can act as a signal of parental quality and prompt differential investment in other aspects of care.It is unknown, however, how these microevolutionary patterns translate to a macroevolutionary scale.2. Here, we investigate potential drivers of variation in the outer and inner volume of open cup nests using a large dataset of nest measurements from 1117 species of passerines breeding in a diverse range of environments. Our dataset is sourced primarily from the nest specimens at the Natural History Museum (UK), complemented with information from ornithological handbooks and online databases.3. We use phylogenetic comparative methods to test long-standing hypotheses about potential macroevolutionary correlates of nest size, namely nest location, clutch size and variables relating to parental care, together with environmental and geographical factors such as temperature, rainfall, latitude and insularity. 4. After controlling for phylogeny and parental body size, we demonstrate that the outer volume of the nest is greater in colder climates, in island-dwelling species and in species that nest on cliffs or rocks. By contrast, the inner cup volume is associated solely with average clutch size, increasing with the number of chicks raised in the nest. We do not find evidence that nest size is related to the length of parental care for nestlings. 5. Our study reveals that the average temperature in the breeding range, along with several key life-history traits and proxies of predation threat, shapes the global interspecific variation in passerine cup nest size. We also showcase the

Variation in nest-building behaviour in birds: a multi-species approach

“…Results of all trees are presented in the supplementary file S3. [20,54]. Varying cup depth could be due to alterations in nest lining, and the explanation for the greater cup depth variation in dome nests than in open cup nests could be that the walls of dome nests simply allow for such variation without posing a risk to nestlings from falling.…”

Beak shape and nest material use in birds

“…In pied flycatchers, for example, nest-material choice varies with material availability [55], while cigarette butts are incorporated into the nests of house sparrows (Passer domesticus) and house finches (Haemorhous mexicanus) at a greater rate in urban environments [56], and the incorporation of wool into great tit nests correlates with the proximity of sheep [57]. Other material preferences, however, seem to be more stable [58,59], and might be driven, for example, by sexual selection or by selection for particular thermal or antipredator properties [33,[60][61][62][63]. Moreover, the correlations that we find here, over and above the effects of phylogenetic signal and sampling biases, do indicate that interspecific variation in the beak shape and in coarse nest material preferences can be linked.…”

Leveraging natural history collections to understand the impacts of global change

“…Two papers highlight how spatial variation in climate and ongoing climate change affect the extended phenotype. In Journal of Animal Ecology , Vanadzina et al (2023) examined how nest size of passerine birds varied along a climatic gradient. Of the 1117 species they examined, 412 came from museum specimens.…”