Fluctuating Environments, Sexual Selection and the Evolution of Flexible Mate Choice in Birds

Environmentally-induced fluctuation in the form and strength of natural selection can drive the evolution of morphology, physiology, and behavior. Here we test the idea that fluctuating climatic conditions may also influence the process of sexual selection by inducing unexpected reversals in the relative quality or sexual attractiveness of potential breeding partners. Although this phenomenon, known as ‘ecological cross-over’, has been documented in a variety of species, it remains unclear the extent to which it has driven the evolution of major interspecific differences in reproductive behavior. We show that after controlling for potentially influential life history and demographic variables, there are significant positive associations between the variability and predictability of annual climatic cycles and the prevalence of infidelity and divorce within populations of a taxonomically diverse array of socially monogamous birds. Our results are consistent with the hypothesis that environmental factors have shaped the evolution of reproductive flexibility and suggest that in the absence of severe time constraints, secondary mate choice behaviors can help prevent, correct, or minimize the negative consequences of ecological cross-overs. Our findings also illustrate how a basic evolutionary process like sexual selection is susceptible to the increasing variability and unpredictability of climatic conditions that is resulting from climate change

Pre-laying vocal activity as a signal of male and nest stand quality in goshawks

In this study we examined male vocalisation patterns as a measure of individual and nest stand quality in goshawk Accipiter gentilis. We related the male call rate at dawn (considered to be part of a reproductive strategy) to breeding success and nest stand structure. We recorded the two main chattering-type calls of nine goshawks during the 3 months preceding egg-laying (January-March). Nest stand characteristics were assessed by means of six parameters of nest trees and four parameters of the forest stands within a 1-ha plot. The vocalisations varied significantly among individuals: successful breeders had longer vocalisations and began vocalising earlier than failed ones. Males that successfully reproduced also differed significantly from unsuccessful ones in nest stand characteristics. The results indicate that dawn vocal activity may be considered a honest advertisement of male quality, as well as the quality of its nest stand, expressed by breeding success. The conservation concerns we may gain about territory quality in relation to male vocal activity are also discussed.Peer Reviewe

Optimal divorce and re-mating strategies for monogamous female birds: A simulation model

International audienc

Predictability and chaos in bird vigilant behavior

While foraging, many animals alternate between feeding and scanning. Spectral analyses of sequences of successive scan and inter-scan durations suggest the existence of a significant non-random, periodic component in the scanning dynamics of some birds. Evidence for cyclic vigilance remains controversial, however. Here data obtained from a purple sandpiper, Calidris maritima, two Barbary doves, Streptopelia risoria, and two choughs, Pyrrhocorax pyrrhocorax were re-analysed by making use of statistical methods from non-linear dynamics. Predictability portraits obtained by subjecting the data to non-linear forecasting support the view that the vigilant behaviour of the two choughs is periodic with superimposed noise. By contrast, the hypothesis of periodic scanning is rejected for the sandpiper and doves, as well as that of pure randomness. Instead, the vigilant behaviour of the sandpiper and doves bears the signature of deterministic chaos: high, short-term, decaying predictability of scan and inter-scan durations. The sequential structure of the data sets makes them well suited for reliable computation of the rate at which predictability declines; results support the conclusion of chaotic patterns. Finally, a mathematical model is developed to investigate some possible functional benefits of periodicity and chaos in vigilant behaviour, compared with random scanning, in terms of the optimization of corporate vigilance of birds foraging in flocks. If individual vigilance is chaotic, then even loose coordination, based on predictions only one foraging bout ahead, can dramatically reduce individual predictability and enhance the level of group surveillance

Host-manipulation by parasites with complex life cycles : adaptive or not ?

The effect of host manipulation by parasites on trophic transmission to final hosts remains unclear. The transmission benefits gained by manipulative parasites are difficult to assess, and evidence for a causal link between manipulation and trophic transmission is missing. In addition, infected intermediate hosts can also be more vulnerable to predation by nonhosts, whereas recent theoretical advances indicate that the evolution of host manipulation does not require increased specificity in trophic transmission. We propose that a deeper consideration of the evolution of complex life cycles in helminth parasites might provide a different perspective on the evolution of host manipulation by parasites