Nightingales sing to show their fathering skills

The song of the male nightingale tells females how good a father he will be, according to a new research.
The study found that better singers will feed their offspring more often, and that they advertise this to potential mates by singing in a more orderly way through repeating song sequences, and using more variable song, including many different 'buzz', 'whistle' and 'trill' songs.
In around 80 per cent of all bird species, males play a key role in raising their young. 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 colouration and courtship behaviour. In nightingales, it is a male's elaborate nocturnal song prior to pair formation that is presumed to be key in advertising their skills as a father.
While male birds are able to sing around 180 different song types, little has been understood on the exact song features that are important.

"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," said lead author Conny Bartsch from Freie Universitat Berlin, Germany.

"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.
"These song features have never been described before in any other species, and include the sequential ordering of songs and the use of acoustic structures that are most probably challenging to produce.
"We were surprised that multiple song features - instead of one 'key' song feature - were related to male feeding effort," Bartsch said.
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.

They studied 20 male nightingales, recording and analysing their nocturnal singing early in the breeding season.
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).
Several different song features were linked to greater paternal efforts by male nightingales. These included having a more ordered singing style - repeatedly singing the same sequential order of song types.

Males that sang more complex song repertoires, indicated by many different 'buzz', 'whistle' and 'trill' song types, also contributed more to chick feeding.