Birds that build closed nests, like the weaver nests shown here, had higher rates of Plasmodium parasites (which are transmitted by mosquitoes) and lower rates of Haemoproteus parasites (transmitted by biting midges) than other birds. The photo shows a colony of Yellow-backed Weaver nests in Queen Elizabeth National Park, Uganda; the inset shows a male Baglafecht Weaver in Malawi, a bird that was included in this study. Photos © Josh Engel