Background Sexual ornamentation may be related to the degree of paternal care
and the ‘good-parent’ model predicts that male secondary characters honestly
advertise paternal investment. In most birds, males are involved in bringing
up the young and successful reproduction highly depends on male contribution
during breeding. In passerines, male song is indicative of male attributes and
for few species it has been shown that song features also signal paternal
investment to females. Males of nightingales Luscinia megarhynchos are famous
for their elaborate singing but so far there is only little knowledge on the
role of male song in intersexual communication, and it is unknown whether male
song predicts male parenting abilities. Results Using RFID technology to
record male feeding visits to the nest, we found that nightingale males
substantially contribute to chick feeding. Also, we analyzed male nocturnal
song with focus on song features that have been shown to signal male quality
before. We found that several song features, namely measures of song
complexity and song sequencing, were correlated with male feeding rates.
Moreover, the combination of these song features had strong predictive power
for male contribution to nestling feeding. Conclusions Since male nightingales
are involved in chick rearing, paternal investment might be a crucial variable
for female mate choice in this species. Females may assess future paternal
care on the basis of song features identified in our study and thus these
features may have evolved to signal direct benefits to females. Additionally
we underline the importance of multiple acoustic cues for female mating
decisions especially in species with complex song such as the nightingale