Identification of vocal individuality in male cuckoos using different analytical techniques

Background: Individuality in vocalizations may provide an effective tool for surveying populations of the Common Cuckoo(Cuculus canorus) but there remains few data on which technique to use to identify individuality. In this research, we compared the within-and between-individual variation in cuckoo calls using two different analytical methods, and discuss the feasibility of using call individuality to count male cuckoos within a population.Methods: We recorded vocalization from 13 males, and measured 15 spectro-temporal variables for each call. The majority of these call variables(n = 12) have greater variation between individuals than within individual. We first calculated the similarity(Pearson's R) for each paired calls in order to find a threshold that could distinguish calls emitted from the same or different males, and then counted the number of males based on this distinction. Second, we used the more widely accepted technique of discriminant function analysis(DFA) to identify individual male cuckoos, and compared the correct rate of classifying individuals between the two analytical methods.Results: Similarity of paired calls from the same male was significantly higher than from different males. Under a relatively broad threshold interval, we achieved a high(>90%) correct rate to distinguish calls and an accurate estimate of male numbers. Based on banded males(n = 3), we found the similarity of paired calls from different days was lower when compared with paired calls from the same day, but this change did not obscure individual identification, as similarity values of paired calls from different days were still larger than the threshold used to distinguish calls from the same or different males. DFA also yielded a high rate(91.9%) of correct classification of individuals.Conclusions: Our study suggests that identifying individual vocalizations can form the basis of an appropriate survey method for counting male cuckoos within a population, provided the performance of different analytical techniques are compared.

Egg-spot matching in common cuckoo parasitism of the oriental reed warbler: effects of host nest availability and egg rejection

Background: The success of cuckoo parasitism is thought to depend largely on the extent of egg matching between cuckoo and host eggs, since poor-matching cuckoo egg would lead to more frequent egg rejection by the host. In this study, we investigated how egg-spot matching between the Common Cuckoo(Cuculus canorus) and its host, the Oriental Reed Warbler(Acrocephalus orientalis) is affected by the local parasitism rate, nest availability in breeding synchronization and egg rejection.Methods: We used the paired design of parasitized and their nearest non-parasitized nests where breeding occurred simultaneously to compare egg-spot matching. The image analysis was used to compare four eggshell pattern variables, namely spot size, density, coverage on the different areas of egg surface, and the distribution on the whole egg surface. Egg recognition experiments were conducted to test the effect of egg spots on egg rejection by the host.Results: Our results show that much better matching in almost all spot parameters tested on the side of the egg and the spot distribution on the whole egg occurred in parasitized nests than in non-parasitized nests. Matching of spot density between cuckoo and host eggs in parasitized nests increased with the synchronization between temporal availability of nests and the egg-laying period of female cuckoos. Egg recognition experiments in which the warbler eggs were deliberately painted with extra spots led to a significantly higher egg rejection rate(78.3%) than of unpainted eggs.Conclusion: Our data suggest that both the high temporal encounter rate between cuckoo and warbler nests as well as the high egg rejection ability of the host are important factors for egg-spot matching of the cuckoos.

The effect of urbanization and exposure to multiple environmental factors on life-history traits and breeding success of Barn Swallows(Hirundo rustica)across China

In addition to landscape changes,urbanization also brings about changes in environmental factors that can affect wildlife.Despite the common referral in the published literature to multiple environmental factors such as light and noise pollution,there is a gap in knowledge about their combined impact.We developed a multidimensional environmental framework to assess the effect of urbanization and multiple environmental factors(light,noise,and temperature)on life-history traits and breeding success of Barn Swallows(Hirundo rustica)across rural to urban gradients in four locations spanning over 2500 km from North to South China.Over a single breeding season,we measured these environmental factors nearby nests and quantified landscape urbanization over a 1km~2radius.We then analysed the relationships between these multiple environmental factors through a principal component analysis and conducted spatially explicit linear-mixed effects models to assess their effect on lifehistory traits and breeding success.We were particularly interested in understanding whether and how Barn Swallows were able to adapt to such environmental conditions associated with urbanization.The results show that there is significant variation in the exposure to environmental conditions experienced by Barn Swallows breeding across urbanization gradients in China.These changes and their effects are complex due to the behavioural responses ameliorating potential negative effects by selecting nesting sites that minimize exposure to environmental factors.However,significant relationships between landscape urbanization,exposure to environmental factors,and life-history traits such as laying date and clutch size were pervasive.Still,the impact on breeding success was,at least in our sample,negligible,suggesting that Barn Swallows are extremely adaptable to a wide range of environmental features.

Saltmarsh vegetation and social environment influence flexible seasonal vigilance strategies for two sympatric migratory curlew species in adjacent coastal habitats

Background:Animals need to adjust their vigilance strategies when foraging between physically contrasting veg-etated and non-vegetated habitats.Vegetated habitats may pose a greater risk for some if vegetation characteristics function as a visual obstruction but benefit others if they serve as protective shelter.Variation in group size,presence of similar species,along with variation in environmental conditions and anthropogenic disturbance can also influence vigilance investment.Methods:In this study,we quantified the vigilance behaviour of two large-bodied,sympatric migratory curlew species-Far Eastern Curlew(Numenius madagascariensis)and Eurasian Curlew(N.arquata)-in vegetated Suaeda salsa saltmarsh and non-vegetated mudflat habitat in Liaohekou National Nature Reserve,China.We used linear mixed models to examine the effects of habitat type,season,tide time,flock size(conspecific and heterospecific),and human disturbance on curlew vigilance investment.Results:Both species spent a higher percentage of time under visual obstruction in S.salsa habitat compared to mudflat habitat but in response,only Far Eastern Curlew increased their percentage of vigilance time,indicating that visual obstruction in this habitat is only a concern for this species.There was no evidence that S.salsa vegetation served as a form of cryptic background colouration since neither species decreased their vigilance effect in S.salsa habitat in spring compared to the autumn migration season.The effect of curlew social environment(i.e.flock size)was habitat dependent since percentage of vigilance time by curlews in saltmarsh increased with both the number of individual curlews and number of other birds present,but not in mudflat habitat.Conclusions:We conclude that both migratory curlew species exhibit a flexible vigilance adjustment strategy to cope with the different environmental and social conditions of adjacent and sharply contrasting coastal habitats,and that the trade-off between the risks of foraging and the abundance of prey may be a relatively common phenom-enon in these and other shorebird populations.

Room-temperature processing of silver submicron fiber mesh for flexible electronics

Ultrathin,patterned,conducting metallic fibers have been extensively studied as building blocks in flexible electronics.However,their scalable processing and attainment of patterns at room temperature is challenging.In this paper,we report on the patterning of ultra-long silver submicron fibers as woven mesh through the process of continuous draw spinning in the presence of ultraviolet(UV)treatment.The silver fibers can be directly intertwined on flexible substrates,such as polyethylene terephthalate(PET)and polyimide(PI).The as obtained silver submicron fiber mesh present excellent photoelectric properties(T=90%,R=9Ωsq^(−1))and outstanding flexibility and can be easily transferred on other surfaces.To demonstrate its application,flexible electrochromic smart window and infrared stealth film have been prepared.