Nest survival rate of Reeves＇s pheasant(Syrmaticus reevesii) based on artificial nest experiments

To explore the nest survival rate of Reeves＇ s pheasant（Syrmaticus reevesii） and the nest-site factors that affect it, we conducted artificial nest experiments with reference to natural nests at Dongzhai National Nature Reserve（DNNR）, Henan Province and Pingjingguan, Hubei Province from April to June 2014 simulating the situation in its early and later breeding season. We also determined distance characteristics of the nest sites by Arc GIS 10.0. Nest survival models were constructed in Program MARK for data analysis. Results indicated that in the early breeding season, the apparent survival rate（ASR） in DNNR（52.4%） was significantly greater than that in Pingjingguan（13.5%）, and the ASR in the later breeding season in DNNR（26.7%） was not indistinctively correlated with Pingjingguan（3.2%）. The daily survival rate（DSR） in the later breeding season was 93.8% in DNNR and 92.0% in Pingjingguan, respectively. The DSRs were both negatively correlated with nest distance to forest edges and settlements. The DSR in Pingjingguan was positively correlated with nest distance to paths and negatively correlated with nest distance to water sources. However, the DSR in DNNR was negatively correlated with nest distance to paths but positively correlated with nest distance to water sources.

The allocation between egg size and clutch size depends on local nest survival rate in a mean of bet-hedging in a shorebird

Background:The allocation of resources between offspring size and number is a central question of life-history theory.Although several studies have tested the existence of this trade-off,few studies have investigated how environmental variation influences the allocation of resources to offspring size and offspring number.Additionally,the relationship between population dynamics and the offspring size and number allocation is far less understood.Methods:We investigate whether resource allocation between egg size and clutch size is influenced by the ambient temperature and whether it may be related to apparent nest survival rate.We measured 1548 eggs from 541 nests of two closely related shorebird species,the Kentish Plover(Charadrius alexandrinus)and the White-faced Plover(C.dealbatus)in China,in four populations that exhibit contrasting ambient environments.We weighed females,monitored nest survival,and calculated the variance of ambient temperature.Results:Although we found that egg size and clutch size were all different between the four breeding populations,the reproductive investment(i.e.total clutch volume)was similar between populations.We also found that populations with a high survival rate had relatively larger eggs and a smaller clutch than populations with a low nest survival rate.The latter result is in line with a conservative/diversified bet-hedging strategy.Conclusions:Our findings suggest that plovers may increasing fitness by investing fewer,larger or many,small according local nest survival rate to make a similar investment in reproduction,and thereby may have an impact on population demography.

Drivers of nest survival rate in a southern Tunisian population of Laughing Doves(Spilopelia senegalensis)

Background:Investigating the ecological factors and processes shaping nest survival is of great importance for assessing the breeding success of bird populations and understanding their spatio-temporal dynamics.Here,this question is addressed for the Laughing Dove(Spilopelia senegalensis),an expanding Afro-tropical bird in the Tunisian oasis habitat.Methods:This study took place in Kettana oasis,in south-eastern Tunisia.Natural Laughing Dove nests were searched for and monitored by means of regular visits,from the discovery date until the end of the breeding attempt(i.e.fledging or failure).Data were then used to investigate the relevance of laying date,nest age(days after clutch initiation),nest height and vegetation structure in the close nest tree environment as predictors of daily nest survival rate,using logistic-exposure models that accounted for heterogeneity in monitoring period among the studied nests.Models including different combinations of covariates were ranked according to their AICc scores,and the modelaveraging technique was used for the assessment of the effects of covariates on daily nest survival rate.Results:Vegetation structure in the close nest tree environment and nest age provided important predictors of daily nest survival rate,whereas neither nest height nor laying date showed significant effects.Daily nest survival rate was negatively associated with the presence of date palm trees in the close nest tree environment,but it was positively related to nest age.Daily nest survival rate was higher during the post-hatching stage than during the pre-hatching stage.Conclusions:Nests placed on fruit trees close to clumps of palm trees suffered higher predation risks compared to those placed on fruit trees situated far from palm trees.This is probably because palm tree clumps provided refuges for nest predators,notably the Black Rat(Rattus rattus)which has been reported to be the main nest predator in the oasis habitat.The predatory activity of this rodent seemed more directed against eggs than nestlings,which may explain the observed increase in daily survival rate with nest age.

Landscape features and weather influence nest survival of a ground-nesting bird of conservation concern,the greater sage-grouse,in humanaltered environments

Introduction:Ground-nesting birds experience high levels of nest predation.However,birds can make selection decisions related to nest site location and characteristics that may result in physical,visual,and olfactory impediments to predators.Methods:We studied daily survival rate[DSR]of greater sage-grouse(Centrocercus urophasianus)from 2008 to 2010 in an area in Wyoming experiencing large-scale alterations to the landscape.We used generalized linear mixed models to model fixed and random effects,and a correlation within nesting attempts,individual birds,and years.Results:Predation of the nest was the most common source of nest failure(84.7%)followed by direct predation of the female(13.6%).Generally,landscape variables at the nest site(≤30 m)were more influential on DSR of nests than features at larger spatial scales.Percentage of shrub canopy cover at the nest site(15-m scale)and distances to natural gas wells and mesic areas had a positive relationship with DSR of nests,whereas distance to roads had a negative relationship with DSR of nests.When added to the vegetation model,maximum wind speed on the day of nest failure and a 1-day lag in precipitation(i.e.,precipitation the day before failure)improved model fit whereby both variables negatively influenced DSR of nests.Conclusions:Nest site characteristics that reduce visibility(i.e.,shrub canopy cover)have the potential to reduce depredation,whereas anthropogenic(i.e.,distance to wells)and mesic landscape features appear to facilitate depredation.Last,predators may be more efficient at locating nests under certain weather conditions(i.e.,high winds and moisture).

Timing of breeding as a determinant of nest success of the vulnerable Chestnut Seedeater(Sporophila cinnamomea)in grasslands of southern South America

The breeding traits of Sporophila seedeaters have been relatively well studied in recent years;nevertheless,a group of ten species in the genus,known as southern capuchinos,remain understudied.That is the case with Chestnut Seedeater(Sporophila cinnamomea),a species vulnerable to extinction,which breeds in the grasslands of southeast South America and,after reproduction,migrates towards the Cerrado region in central Brazil.Here,we investigated breeding ecology and calculated average clutch size,productivity,the sex ratio of nestlings,and estimated nest success.Then we tested(1)whether there is a relationship between the number of active nests and environmental variables,(2)whether the nestling sex ratio deviates from the 1:1 ratio,(3)whether clutch size varies between breeding seasons,and(4)whether the nest success is related to starting date,nest age,plant support,nest height from the ground,and clutch size.During two breeding seasons(October-March 2018-2020),we monitored 98 nests.We generated survival models with five interacting covariates to assess the survival of the nests.We recorded the entire breeding period for Chestnut Seedeater,which was estimated to be 4.6 months,similar to other migratory seedeaters.Clutch size did not differ between breeding seasons.The sex ratio of nestlings was not significantly different from the 1:1 ratio.Nest success was 31%,and predation was the leading cause of unsuccessful nests(83%).The daily survival rate was 0.95±0.01.The main predictor of nest survival was the covariate starting date.These findings,added to other aspects of the species’natural history described here,may help illuminate the ecology and behavior of Chestnut Seedeater and other southern endangered capuchinos,and grassland-dependent species of South America.

Research activity does not affect nest predation rates of the Silver-throated Tit,a passerine bird building domed nests

Background:Research activities have often been thought to potentially influence avian nesting success by increasing nest predation rates.Although recent studies of species building open nests and cavity nests suggest that research disturbance does not generally induce nest predation,whether it is also the case in species building domednests remains unknown.In birds,domed-nest species exist in about half of the passerine families,and research disturbance to the domed nests may differ from that to the nests of other types for their different nest structures.Methods:We investigated if research activities affected nest predation rate by analyzing the relationships of the daily nest survival rate with the research activities at the egg and nestling stages of a domed-nest species,the Silverthroated Tit(Aegithalos glaucogularis).Results:Our results showed that nest daily survival rate was significantly affected by the laying date and nest age during the egg stage,and by the hatching date only during the nestling stage.By contrast,there were no significant effects of research activities,in terms of visiting nests and filming nests,on the nest survival of the Silver-throated Tit at both the egg and nestling stages.Conclusions:Our results coincide with the findings in species building other types of nests that research activities do not always have negative effects on avian nesting success.

The breeding biology of endemic Spectacled Parrotbill(Sinosuthora conspicillatus) in Lianhuashan National Nature Reserve, Gansu Province, China

Background: Life history traits play critical roles in population survival and evolution.Breeding information should be particularly detailed in order to provide significant insights into the population status and the evolution of other traits.To our knowledge, there is still no information about the breeding biology of Spectacled Parrotbill(Sinosuthora conspicillatus), an endemic parrotbill in China.Methods: We searched the nests, checked all nests found and recorded the information of eggs, nestlings and nest sites of the Spectacled Parrotbill from 2013 to 2015 at Lianhuashan National Nature Reserve in Gansu Province, China.Results: A total of 16 nests were found.Nest trees were artificial young spruces and honeysuckles.Mean nest height was 0.89 ± 0.47 m(n = 16) above the ground level.All nests were cup-shaped and constructed using leaves, fine strips of barks and grasses by both parents.The mean clutch size was 4.42 ± 0.79(n = 12).The eggs were oval in pale blue without speckles, and the mean egg mass was 1.25 ± 0.07 g(n = 27).The egg length was 15.56 ± 0.46 mm(n = 27) and the width was 12.46 ± 0.29 mm(n = 27).Incubation period was 13 days and nestling period was 13–14 days.The breeding success rate was 46%, and among those failed nest, 71% were depredated and 29% were deserted.Conclusion: Detailed life history information about parrotbill is still limited.The breeding biology of Spectacled Parrotbill reported in the present study should be helpful for further research about population, breeding behavior and conservation of this bird.

Long-term monitoring data reveal effects of age,population density,and environmental aspects on hatching success of Common Cranes(Grus grus)

Facing climate and land use change,a species’ability to successfully adapt to changing environments is crucial for its survival.Extensive drainage and intensification of agriculture and forestry set wetlands and associated species at risk of population declines.The population of Common Cranes(Grus grus)has experienced considerable fluctuations over the last century.Despite increasing population numbers,hatching success seemed to have decreased over the last years.The aim of this study was to identify factors influencing hatching success and nest survival of Common Cranes based on analyses of long-term individual-based monitoring data from northeastern Germany and evaluate the species ability to adapt to changing environments.Hatching success decreased over the course of the study period from 0.75 to 0.55.Surprisingly,nest survival and hatching success did not vary across different nesting habitats,whereas factors such as female age,timing of nest initiation and breeding pair density were found to have significant effects on hatching success.Older females showed higher hatching success,even though the proportion of unhatched eggs was highest in females aged 20 years or older.Early nest initiation had a positive effect on hatching success.Water levels are more favorable early in the nesting season,whereas increasing evaporation with time causes water levels to decrease,granting easier access for predators.Independently of female age,hatching success decreased with increasing numbers of breeding pairs within a 2-km radius around a nesting site.High population densities intensify competition for resources and promote intraspecific interactions,affecting reproductive outcome negatively.This study gives first insights into mechanisms behind population regulation in Common Cranes,highlighting the importance of population dynamics and individual features.We suggest to further investigate density dependent effects including landscape and habitat features as well as reproductive success in terms of chick survival,since successfully raising juveniles is crucial for a species survival.