10.5061/DRYAD.W6M905QP5
Santema, Peter
0000-0002-5765-3067
Max Planck Institute for Ornithology
Kempenaers, Bart
0000-0002-7505-5458
Max Planck Institute for Ornithology
Offspring provisioning by extra-pair males in blue tits
Dryad
dataset
2021
Max Planck Society
https://ror.org/01hhn8329
2021-03-03T00:00:00Z
2021-03-03T00:00:00Z
en
10877 bytes
2
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Most birds are socially monogamous with both parents providing offspring
care, but sometimes individuals are observed to provision at a nest that
is not their own. One possible explanation for this behaviour is that it
is a fitness maximising strategy by males who have copulated with the
female and hence potentially sired extra-pair offspring in the focal nest.
Over a period of 8 years and among a total of 854 nests, we observed 12
blue tits Cyanistes caeruleus that provisioned at a nest that was not
their own. In all cases, the provisioning individual was a male who had no
nestlings of its own, either because its breeding attempt had failed
(n=5), because it was a non-breeder (n=6) or because the eggs in its own
nest had not hatched yet (n=1). Only two out of the 12 males had sired
offspring in the nest where they helped, but most others had had
interactions with the female during her presumed fertile period or were
close neighbours, and hence may have performed extra-pair copulations that
did not result in fertilisations. In 10 out of the 12 cases, the resident
male was not present anymore, either because it had disappeared (n=7) or
because it was socially polygynous and provided care at its other, primary
nest (n=3). Our findings suggest that females can benefit from extra-pair
copulations by obtaining help in raising their brood when they do not
receive help from their social mate. Extra-pair copulations could thus
function as an “insurance” strategy with a relatively small cost.