Winter associations predict social and extra-pair mating patterns in blue tits. Researchers of the Max Planck Institutes for Ornithology in Seewiesen and for Animal Behavior in Radolfzell show in their new study that blue tits that often foraged together during winter were more likely to end up as breeding pairs or as extra-pair partners, whereby bonds between future breeding partners seem to establish earlier in winter than those between future extra-pair partners.