Differential colour-ring loss among Dalmatian Pelican(Pelecanus crispus) colonies and its consequence on survival estimates

The analysis of bird ringing data often comes with some potential sources of error and bias,as ring wear and/or loss could affect mark-recapture analyses and produce erroneous estimates of survival.Furthermore,ring wear and loss rates may differ between and within species based on the habitat they use or the species’ life-history traits and behaviour as well as the type of the ring.In this study we use resighting data from a long-term double marking experiment to directly estimate the rate of colour-ring loss among different Dalmatian Pelican colonies over time,evaluate any possible factors that could contribute to differential ring loss and assess how it may bias the results of mark-resighting analyses.Based on 14,849 resightings from 1275 individuals and using multi-state continuous-time hidden Markov models(HMMs) we showed that probability of ring loss was markedly different among colonies,ranging from 0.10 to 0.42 within the first year of marking,whereas the cumulative probability of losing a ring after ten years ranged 0.64 to 0.99.These rates are among the highest estimated when compared to previous studies in waterbirds.Our approach assessing the intra-specific variance in ring loss provided several factors potentially involved,such as the use of glue and the fledgling age accuracy and we could further hypothesise the effect of environmental factors.Finally,our results showed that ring loss can be a significant challenge for the assessment of the species’ population dynamics using mark-recapture methods as survival was consistently underestimated when not accounting for ring loss and varied significantly among different colonies.

Recapture probability, flight morphology, and microorganisms

Microorganisms on and within organisms are ubiquitous and interactions with their hosts range from mutualistic over commensal, to pathogenic. We hypothesized that microorganisms might affect the ability of barn swallows Hirundo rustica to escape from potential predators, with positive associations between the abundance of microorganisms and escape ability implying mutualistic effects, while negative associations would imply antagonistic effects. We quantified escape behavior as the ability to avoid capture in a mist net and hence as a small number of recaptures. Because recapture probability may also depend on timing of reproduction and reproductive success, we also tested whether the association between recapture and microorganisms was mediated by an association between recapture and life history. We found intermediate to strong positive relationships between recapture probability and abundance of Bacillus megaterium, but not abundance of other bacteria or fungi. The abundance of B. megaterium was associated with an advance in laying date and an increase in reproductive success. However, these effects were independent of the number of recaptures. This interpretation is supported by the fact that there was no direct correlation between laying date and reproductive success on one hand and the number of recaptures on the other. These findings have implications not only for predator-prey interactions, but also for capture-mark-recapture analyses of vital rates such as survival and dispersal.

Spatial distribution of Vespa velutina individuals hunting at domestic honeybee hives： heterogeneity at a local scale

Since its recent introduction into Europe, the yellow-legged hornet, Vespa velutina, has become a major predator of the domestic honeybee, Apis mellifera, but little is known about its hunting behavior. We studied V. velutina hunting behavior by a capture- mark-recapture procedure in an experimental apiary. A total of 360 hornets were captured and tagged, and we determined： （i） the number of hornets visiting the apiary and the changes in time, （ii） the average number of individual visits per half-day and the time elapsed between consecutive recaptures, and （iii） the individual and global distribution of the hornets in the apiary. More than 50% of the marked hornets were recaptured at least once, this increased to 74% in considering the first marked individuals. We estimated 350 hornets visiting the patch daily with at least 1 visit per half-day. The number of marked hornets decreased over time while the number of unmarked ones increased, suggesting a turnover of individuals. The reduction of the delay between consecutive visits indicates that hornets became more efficient over time. Most of the hornets （88%） were recaptured in front of different hives but, overall, the global distribution was aggregative. Hornets were mainly recaptured in front of 1 hive which was neither the smallest nor the biggest colony, suggesting that the major cue used by hornets is not the amount of food. We hypothesize that the defensive behavior of the honeybee colony could explain our results which may be promising to further studies.

Contrasting demographic trends and asymmetric migration rates in a spatially structured amphibian population

N_(a)tural populations often persist at the landscape scale as metapopulations,with breeding units(subpopulations)experiencing temporal extinction and recolonization events.Important parameters to forecast population viability in these systems include the ratio of the effective number of breeders(N_(b))to the total number of adults(N_(a))and migration rates among subpopulations.Here,we present the results of a 10-year integrative monitoring program of a metapopulation of the Iberian green frog(Pelophylax perezi)in central Spain.We characterized population dynamics at two main breeding ponds(Gravera and Laguna)using capture-mark-recapture data to estimate N_(a)in each breeding season,and multilocus genotypes to estimate the effective population size(Ne),N_(b),individual breeding success,and migration rates.Both ponds experienced population decline after a dry season,with Gravera subsequently recovering and Laguna suffering a bottleneck associated with genetic impoverishment.In this subpopulation,average allelic richness and private alleles decreased from 2010(10.87 and 1.67,respectively)to 2018(8.0 and 0.20).The N_(b)/N_(a)ratio in Laguna in 2018 was twice as high(0.95)than in Gravera(0.41)or in pre-bottleneck Laguna(0.50),suggesting plasticity or genetic compensation through increased individual breeding success.Migration rates were asymmetric between ponds,with a stronger contribution from Gravera to Laguna(29.9%vs.16.2%in the opposite direction)that may result in a rescue effect.This study emphasizes the importance of integrative demographic approaches for the monitoring of natural populations based on a better understanding of their spatio-temporal dynamics,which provides valuable information for conservation actions.

Developing, testing and application of rodent population dynamics and capture models based on an adjusted Leslie matrix-based population approach

Small rodents in general and the multimammate rat Apodemus agrarius in particular, damage crops and cause major economic losses in China. Therefore, accurate predic- tions of the population size of A. agrarius and an efficient control strategy are urgently needed. We developed a population dynamics model by applying a Leslie matrix method, and a capture model based on optimal harvesting theory for A. agrarius. Our models were parametrized using demographic estimates from a capture-mark-recapture （CMR） study conducted on the Qinshui Forest Farm in Northwestern China. The population dynamics model incorporated 12 equally balanced age groups and included immigra- tion and emigration parameters. The model was evaluated by assessing the predictions for four years based on the known starting population in 2004 from the 2004-2007 CMR data. The capture model incorporated two functional age categories （juvenile and adult） and used density-dependent and density-independent factors. The models were used to assess the effect of rodent control measures between 2004 and 2023 on population dynamics and the resulting numbers of rats. Three control measures affecting survival rates were considered. We found that the predicted population dynamics of A. agrarius between 2004 and 2007 compared favorably with the observed population dynamics. The models predicted that the population sizes of A. agrarius in the period between 2004 and 2023 under the control measure applied in August 2004 were very similar to the optimal population sizes, and no significant difference was found between the two pop- ulation sizes. We recommend using the population dynamics and capture models based on CMR-estimated demographic schedules for rodent, provided these data are available.The models that we have developed have the potential to play an important role in pre- dicting the effects of rodent management and in evaluating different control strategies.