Scientists from the University of Granada, in collaboration with the South African University of the Witwatersrand and the Percy FitzPatrick Institute Center of Excellence at the University of Cape Town, have concluded that female house sparrows ( Passer domesticas ) invest energy in the laying of eggs according to the ability of the male to fill the nest with feathers , which serve to isolate the chicks from the cold and keep them alive.
The researchers observed the behavior of 50 pairs of sparrows in the natural environment of the island of Dassen (South Africa). According to their results, the transport of the feathers could be the product of sexual selection by the females , since they invest more energy in reproduction if they have more feathers in the nest. “They are a great insulator and the females know that fewer chickens will die if the male wears more feathers,” says Lola García López de Hierro, principal investigator of the study, in statements to the SINC agency.
For the study, the researchers removed and feathered the nests of the fifty pairs of sparrows in different stages of reproduction of these birds. A first phase consisted of observing for one hour the behavior of pairs with young less than five days old to record various variables and see their behavior if they removed a series of feathers or if they left them. Later they repeated the experiment with chickens older than ten days.
“For the tests we had footage of the nest in which we collected the behaviors of the sparrows and, with a table of variables, we concluded that the more feathers there were in the nest, the greater number of eggs the sparrow females laid”, adds García- López de Hierro. They also observed that when the females detected that they were missing feathers in the nest they called their males in an exaggerated way , to which the sparrows responded by carrying more feathers and performing a dance around the female when they returned.
