Father's Day findings: Good singers make the best nightingale fathers

Sunday's Google Doodle honors Father's Day by highlighting the fatherhood skills of a penguin, fox, human, and more – but maybe they should have included a nightingale father.

Research on nightingale parenting abilities arrived just in time for Father’s Day: It turns out that a male nightingale's singing correlates to how good a parent he will be. (For many bird species, including penguins and nightingales, males play a key role in raising the baby chicks.) 

Male nightingales court mates through song, and males are able to sing close to 180 different song types. While a lot of research has been done about their song type, not as much was known about how females are able to assess their partner’s parenting capabilities – until now. 

Prior research led scientists to believe that only the size of the vocal repertoire of male birds was important. However, findings presented this week in the scientific journal BioMed Central show otherwise.

“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 Freie University in Berlin in a press release.

Twenty male nightingales were tracked from the start of their nesting season in Potsdam, Germany. Why the start of nesting season? Because males only use their nocturnal songs in the early stages of nesting, then cease once they have paired off with a mate. After recording hours worth of songs, the tunes of the mating calls were analyzed and categorized according to the types of sounds made, including buzzes, whistles, and trills.

Birds with “better” songs were considered to be those which had the widest buzz, whistle, and trill repertoires who also sang “orderly” songs. All four song measures were found to have positive correlations with the rates at which the fathers would feed their offspring.

Next in the study, an antenna was placed near the rim of the nest and a transmitter was attached to the leg of the father nightingale to record the number of times the male would return to the nest, an indicator of how often he brought food for his chicks.

Prior research indicates that the number of times a male will feed his nestlings also depends on the number of hatchlings in the nest, as well as the year. Ms. Bartsch and her team observed and calculated the feeding rate in the early morning and early evening, after determining that these were the most critical time periods for feeding the baby birds.

The study found that fatherly feeding efforts could be accurately predicted from the quality of their songs. This study provides the first link between the sequential ordering of songs (“song orderliness”) and care provided by a father bird.