Parent-offspring and inter-offspring responses to conspecific versus heterospecific distress calls in 2 sympatric birds

Distress calls,as a type of alarm call,play important roles in expressing bodily condition and conveying information concerning predation threats.In this study,we examined the communication via distress calls in parent–offspring and inter-offspring interactions.First,we used playback of chick distress calls of 2 sympatric breeders,the vinous-throated parrotbill Sinosuthora webbiana and the oriental reed warbler Acrocephalus orientalis,to the adults/chicks of these 2 species,respectively,and measured the responses of conspecifics or heterospecifics.The playback-to-chicks experiment showed that both species of chicks reduced the number of begging calls and begging duration time as a response to conspecific/heterospecific distress calls compared with natural begging and background noise controls.However,reed warbler chicks also reduced beak opening frequency in the response to conspecific distress calls compared with other playback stimuli.Second,the results of the playback-to-adults experiment showed that reed warbler adults could eavesdrop on distress calls of conspecific neighbors and sympatric heterospecifics.Furthermore,the nest-leaving behavior of reed warblers did not differ significantly when they heard the distress calls of conspecifics or parrotbills.Finally,reed warbler adults responded to heterospecific distress calls more quickly than to conspecific distress calls,and parrotbill adults presented the same response.Our results supported the warnkin hypothesis and show that chick distress calls play an important role in conveying risk and the condition of chicks to enhance individual fitness.In addition,we also found that eavesdropping on distress calls is a congenital behavior that begins in the chick stage.

Low heritability of social phenotypes in a nonpasserine waterbird

Most behavioral traits are known to be weakly heritable,possibly due to their extreme complexity and flexibility.Despite this general pattern,within-species variation in avian colony size choice has been reported to have a strong additive genetic component,but we are aware of no attempts to assess the heritability of avian sociality at the finer spatial scale.Here,we used an animal model and parent-offspring regression to quantify additive genetic variance in social phenotype(local nesting density)in a nonpasserine waterbird,the common tern Sterna hirundo.For this purpose,we used a novel experimental framework,where variation in the social environment was generated by providing birds with artificial patches of attractive nesting substrate that markedly varied in size.During 2011-2019,we collected data on social preferences for either low or high nesting density in over 250 individuals,either kin(mostly parent-offspring relationships)or non-kin recorded breeding multiple times across years.All heritability estimates of local nesting density were low(<0.10),irrespectively of fixed effects(sex and year)included in the models,data used in the modeling(all individuals vs.early recruits),or methodological approach(animal model vs.parent-offspring regression).We conclude that avian sociality,as measured at the local scale,may be much less heritable than colony size choice,as measured at the landscape level.Our study adds to the understanding of additive genetic variance in avian behavior,and it underlines a scale dependency in the heritability of behavioral traits.

Host plant choice in the comma butterfly-larval choosiness may ameliorate effects of indiscriminate oviposition

In most phytophagous insects, the larval diet strongly affects future fitness and in species that do not feed on plant parts as adults, larval diet is the main source of nitrogen. In many of these insect-host plant systems, the immature larvae are considered to be fully dependent on the choice of the mothers, who, in turn, possess a highly developed host recognition system. This circumstance allows for a potential mother-offspring conflict, resulting in the female maximizing her fecundity at the expense of larval performance on suboptimal hosts. In two experiments, we aimed to investigate this relationship in the polyphagous comma butterfly, Polygonia c-album, by comparing the relative acceptance of low- and medium-ranked hosts between females and neonate larvae both within individuals between life stages, and between mothers and their offspring. The study shows a variation between females in oviposition acceptance of low-ranked hosts, and that the degree of acceptance in the mothers correlates with the probability of acceptance of the same host in the larvae. We also found a negative relationship between stages within individuals as there was a higher acceptance of lower ranked hosts in females who had abandoned said host as a larva. Notably, however, neonate larvae of the comma butterfly did not unconditionally accept to feed from the least favorable host species even when it was the only food source. Our results suggest the possibility that the disadvantages associated with a generalist oviposition strategy can be decreased by larval participation in host plant choice.