Female extra-pair behavior is not associated with reduced paternal care in Thorn-tailed Rayadito

Extra-pair behavior is present in 76% of socially monogamous bird species
with biparental care. This behavior may produce costs to females related
to a reduction in paternal care. We estimated the percentage of extra-pair
offspring and quantified paternal care in 44 nests of Thorn-tailed
Rayadito (Aphrastura spinicauda) to assess whether males reduce their
parental care when females obtain extra-pair fertilizations. We used data
from a sub-Antarctic population of Rayadito located on Navarino Island
(55°4′S, 67°40′W), southern Chile. We found no statistical support for a
relationship between variation in paternal care and the percentage of
extra-pair offspring. We discuss how the inability of breeding males to
assess their genetic paternity and potential restrictions on behavioral
flexibility may explain this result. Additionally, if paternal care is
subjected to sexual selection, this could limit a facultative response to
female extra-pair behavior by males. Finally, it is possible that a
reduction in paternal care might not have evolved in this particular
locality given the low frequency of extra-pair paternity in our study
population.