To our knowledge, our study is the first that investigates repeatability of offspring desertion behavior in nature.
Our main results are that female penduline tits are consistent in their desertion behavior, and male behavior is predicted by ambient environment, in terms of early versus late season.
Since both abiotic and biotic variables (e.g. ambient temperature, day length, food availability) and the social environment (e.g. the number of potential mates) often vary over the breeding season, desertion behavior, if it depends on some of these variables, should reflect seasonal variation.
Offspring desertion is a wide-spread behavior, and its frequency often varies within populations.
Research has also shown that parasitic infections can negatively impact reproductive success by delaying arrival to the breeding grounds [56], reducing clutch sizes [47], [54], [57], reducing nest defense behavior [58], [59], increasing probability of clutch desertion [60], reducing hatching success [47], [60], reducing fledging success [47], and siring nestlings with poorer body condition [57].
We are currently pursuing the latter proposition by analyzing the behavior of males and females immediately preceding desertion (van Dijk et al, in prep).
The functional analysis of behavioral consequences suggests a way to understand the underlying mechanisms of behavior change and how the short-term adoption, but long-term desertion, of key behaviors might be understood.
Females lead courtship behavior, actively compete for mates, regulate time of their own desertion as mates, and copulate with consecutive partners (Valle 2009, 2013).
Thus, one should expect major fitness benefits of compensatory parental behavior for both sexes, increasing with the risk of parental desertion and with decreasing costs of care.
Theories on parental decision making suggest that such compensatory behavior by A. femoralis females could be exploited by males through clutch desertion (cf. Székely et al. 1996, Barta et al. 2002).
Thus, in species where sex-specific parental roles have evolved, the loss of one parent, either because of active brood desertion or due to death, might lead to a spontaneous change of the sex-specific caring behavior in the remaining parent.
