A pair of Moluccan Red Lories, Eos bornea rothschildi (upper
right and lower left (upside down)), and a pair of Rainbow
Lorikeet, Trichoglossus haematodus haematodus (center; one bird
is hanging upside down), near the north coast of Seram,
Indonesia. Image: Kevin Sharp [wallpaper size]. Birds in Science
The ability to ramp up testosterone levels drives certain male
sparrows to mate, but also makes them bad dads, a new study
suggests. Researchers had thought that the total amount of
testosterone might determine the mating habits and aggressive
tendencies of male dark-eyed juncos, a type of sparrow. But the
new study of juncos in the wild showed that the speed with which
testosterone levels can rise and fall also plays an important
role in determining whether dad stayed around to help care for
the kids. “This study is one of the first to show for a songbird
living in the field under natural conditions that individual
variation in the hormone testosterone maps onto variation in
aggression and parental behavior,”