20.04.2022: To date, surprisingly little scientific information is available regarding the behaviour of birds and their offspring. A recent international study led by the University of Veterinary Medicine Vienna now shows that the influence of weather is a determining factor affecting aspects such as breeding performance, food supply and nest use. According to the research team, the findings are also of great relevance for nature conservation and provide new insights into the theoretical basis of habitat selection.

Choosing a proper habitat is an important decision of an individual that influences life expectancy and relative survival rate (evolutionary fitness). Habitat choice can involve a variety of aspects of life, including the choice of a proper foraging and roosting site. For birds, however, little scientific information has been available to date on habitat use, in early developmental stages, e.g. in nestlings, especially with regard to nest space use. Bird nests are of great importance to protect eggs and offspring from environmental factors such as weather hazards and exposure to predators.

Weather conditions determine use in the nest

The recently published study by Vetmeduni investigates the influence of different weather conditions on breeding performance, food supply and nest-use in hoopoe chicks (Upupa epops). The study’s author, Herbert Hoi from the Konrad Lorenz Institute of Ethology at Vetmeduni, explains: “In particular, the place where the parents hand over the food and the size of the prey can lead to different use of the nest space by the nestlings. Parental feeding strategy and prey size are, in turn, influenced by weather conditions, which are the most important determinants of nest interior use by chicks.” The study also provides important new insights into communication between parents and their offspring.

You are what you eat: prey size makes all the difference

For their study, the international research team used camera recordings of 88 hoopoe nests. In excessively humid weather, the chicks spent more time under the entrance hole when small prey was delivered. Nestlings provided with large prey, on the other hand, more often remained hidden in a more distant area of the nest, in any weather condition. This makes prey the most important factor directly influencing nest-space use, suggesting a crucial role of large insects for hoopoes. Long-term effects of weather were also shown to influence the overall food supply provided to the nestlings, thus affecting offspring behaviour. It is therefore to be expected that climate changes will have consequences for the population of the hoopoe. Other important variables include the available nest space and the environmental conditions around the nest. These are relevant for nestling strategies and behaviours, including social interactions between nest mates, which further affects the probability of survival of the young birds.

Implications for conservation issues and habitat selection theory

According to Hoi, the results of the study seem to be of great importance for the theoretical background of habitat selection in birds in general, especially regarding the early development of habitat preferences (imprinting) and use. “Our findings may also have implications for conservation issues, as nestling behaviour may be used as a predictor of environmental quality,” says Hoi.