The spatial distribution and breeding behavior of neighbors affect the reproductive success of tits

The spatial distribution and breeding behavior of neighboring birds(conspecific and heterospecific)may influence reproduction and the effects differ across species.In this study,we investigated intra-and inter-specific spatial distribution of breeding via artificial nestboxes and examined whether overlap with neighbors affected reproductive success of the focal breeding pair.Regarding spatial distribution,Varied Tits(Sittiparus varius)and Cinereous Tits(Parus cinereus)showed similar pattern:distances of nestboxes containing conspecific tits were greater than those with heterospecific ones.In terms of breeding behavior,reproductive success was not significantly related to the distance from their neighbor’s nest.The reproductive success of Varied Tits was significantly related to that of their neighbors,while in Cinereous Tits,no strong link was found to any recorded reproductive behavior of the neighbors.These findings explain spatial variation in nest site selection of Varied Tits and Cinereous Tits.Reproductive success rate of Varied Tits is affected by that of the neighbors while that of Cinereous Tits is not.The results highlight that there are differences in reproductive outcome among related species and offer suggestions on the use of artificial nestboxes in experiment and conservation programs.

Geographical variation in nest defense among cinereous tit populations in China

Behavioral divergence among populations is common across taxonomic groups,still we know very little about anti-predator behaviors.Animal exposure to predation risk is variable in different ecological contexts.In addition,reproduction value of animals in different geographical regions usually varies.In this study,we tested whether cinereous tits Parus cinereus in different populations exhibited nest defense behaviors similar to those of nest or adult predators and whether their nest defense behaviors showed geographical variation.By using field dummy experiments,we observed tits’nest defense behavior in nest predator common chipmunk Tamias sibiricus and red squirrel Sciurus vulgaris,adult predator Eurasian sparrowhawk Accipiter nisus and nonthreatening species Oriental turtle dove Streptopelia orientalis in the ZJ(44°N),DZ(31°N),and DLS(18°N)populations,respectively.The response scores varied significantly across the 4 dummies in ZJ-tits and DLS-tits but did not in DZ-tits.When facing the chipmunk,ZJ-tits showed the highest response score and DZ-tits showed the lowest response score.When facing the squirrel,ZJ-tits showed a higher response score than tits in the other 2 populations.However,tits among the 3 populations responded similarly to a sparrowhawk or dove with slight response behaviors.In addition,response scores to nest predators were positively correlated with brood size across the 3 populations,but no trend was found for sparrowhawks or doves.Our results indicated that the nest defense behaviors of cinereous tits have evolved in response to large-scale geographical variation in ecological contexts and reproduction value.

Differently sized cuckoos pose different threats to hosts

Hole-nesting tits Parus spp.have been classified as"unsuitable"hosts for cuckoo parasitism because cuckoos cannot enter a cavity if the entrance is too small.However,Chinese tits could re-ject alien eggs and egg ejection rate increased with the local diversity of parasitic cuckoo species.Antiparasitic behavior among Chinese tits may have evolved due to greater size variation among sympatric cuckoo species.This raises the question of whether differently sized parasitic cuckoos pose different threats to Chinese tits.A green-backed tit Parus monticolus population that is sym-patric with Asian emerald cuckoo Chrysococcyx maculatus(eme-cuckoo,small-sized parasite)and common cuckoo Cuculus canorus(com-cuckoo,large-sized parasite),and a cinereous tit P.cinereus population that is only sympatric with com-cuckoo were chosen as study organisms.We observed behavioral response and recorded alarm calls of the 2 tit species to eme-cuckoo,com-cuckoo,chipmunk Tamias sibiricus(a nest predator)and dove Streptopelia orientalis(a harm-less control),and subsequently played back alarm calls to conspecific incubating females.In dummy experiments,both tit species performed intense response behavior to chipmunk,but rarely responded strongly to the 3 avian species.In playback experiments,both tit species responded strongly to conspecific chipmunk alarm calls,but rarely responded to dove alarm calls.The inten-sity of response of incubating female green-backed tits to eme-cuckoo and com-cuckoo alarm calls were similar to that of chipmunk alarm calls,while the intensity to eme-cuckoo alarm calls was higher than the intensity to dove alarm calls which was similar to that of com-cuckoo alarm calls.In contrast,few female cinereous tits responded to eme-cuckoo and com-cuckoo alarm calls.These findings indicated that the threat level of eme-cuckoo was slightly greater than that of com-cuckoo for sympatric green-backed tits,but not for allopatric cinereous tits.

Responses of incubating females to female cuckoo calls in 2 hole-nesting bird species

Acoustic signals play an important role in animal communication systems,and these signals can transfer diverse and meaningful information from a signaler to a receiver(e.g.,Yu et al.2019).Animal signals tend to be honest;however,deception can occur when it is beneficial for receivers to send dishonest signals,such as by mimicking alarm calls to steal food from other individuals(Flower et al.2014).In birds,vocal mimicry is a widespread phenomenon that has 2 major functional explanation categories:intraspecific and interspecific communications(Dalziell et al.2015).Vocal mimicry in intraspecific communication mainly involves sexual selection and social affiliation(Dalziell et al.2015).In interspecific communication,studies on vocal mimicry are mostly related to predator–prey interactions(Dalziell et al.2015).Mimics could mimic calls of predators to scare off other predators or competitors.For example,some species of hole-nesting birds produce a snakelike hissing call to drive nest predators away(e.g.,Dutour et al.2020).Receiver should be particularly sensitive to the deceptive vocals of mimics if failing to respond to an actual model sound is costly.Therefore,the mimics could derive an advantage from mimicking the calls of predators of the receivers.A recent experimental study suggested that the bubbling calls of female common cuckoo Cuculus canorus mimic those of Eurasian sparrowhawk Accipiter nisus,and they primarily serve to distract regular hosts after laying eggs(York and Davies 2017).However,Xia et al.(2019)found that female cuckoo calls have other functions,including attracting mates and repelling rivals.