May 7, 2013 — An international team lead by the University of Granada has found that female sparrows will invest more energy into laying eggs according to the male's ability to fill the nest with feathers which serve to insulate the chicks from the cold and keep them alive.
Scientists from the University of Granada, in collaboration with the South African University of the Witwatersrand and the Percy FitzPatrick Institute at the University of Cape Town, have discovered that the female house sparrow (Passer domesticus) invests more energy into laying eggs when the male brings more feathers to the nest.
"We conducted an experiment with two types of treatments and a control group. In total, we observed the behaviour of 50 pairs of sparrows," Lola García López de Hierro, the study's main researcher, said.
According to their results, carrying feathers could be a result of sexual selection by the females as they put more energy into reproduction if they have more feathers in the nest. "They provide excellent insulation and the females know that less chicks will die if the male brings more feathers," the expert stated.
The experiment was conducted in the natural environment of Dassen Island (South Africa) and this is the first time this behaviour has been documented in the house sparrow.
Taking away and adding feathers
The researchers took away and added feathers to the nests of the fifty pairs of sparrows during these birds' different mating seasons.