The male nightingale sings songs to tell females how good a father he will be, a new study shows.
Better singers feed their offspring more often and they show off this to potential mates by singing in a more orderly way.
In around 80 percent of all bird species, males play a key role in raising their young.
"It has long been thought that a single feature -- the size of a bird's song repertoire -- may be important for females during mate choice. But our study shows that, in nightingales, it is a mix of specific song features that seem to be more important in determining their paternal efforts," said lead author Conny Bartsch from the Freie Universitat Berlin, Germany.
Male nightingales feed the female during incubation, provide food to chicks and defend the nest against predators.
A male's parental skills are, therefore, likely to be a crucial factor for females when choosing a mate.
Female birds assess paternal qualities on the basis of traits, including plumage coloration and courtship behaviour.
The researchers studied the link between the quality of a male song before pair formation, and how good a parent he then was, based on the rate at which he provided food to his chicks.
Following pair formation, they analysed video footage of their nests and data from electronic tags attached to the birds to record male visits and determine the level of paternal care.
They found that male nightingales contribute substantially to chick feeding, at an equal level to females (around 16 nest visits per hour on average).
Ordered singing could serve as an indicator of experience with the breeding grounds, and could mean further benefits for females choosing males with this singing quality, concluded the authors.
The study appeared in BMC Evolutionary Biology.
