Using light-level geolocations to monitor incubation behaviour of a cavity-nesting bird Apus apus pekinensis

The Beijing Swift(Apus apus pekinensis)is a typical cavity-nesting bird that often nests inside holes and crevices in old architectures.Direct observation of their breeding behaviour is challenging and their breeding ecology is thus poorly studied.In this study,we analysed light-level geolocation data collected from six Beijing Swifts for the first time.Our results showed that geolocators can make comprehensive inference of their incubation period and behaviour.As a cost-effective and non-invasive method,geolocators can not only facilitate discovering migration routes,but also can be widely applied in the study of avian reproductive behaviour,especially in cavity-nesting bird species.We further discussed the characteristics and merits of this method and compared with other conventional nest-monitoring methods in recording birds.

Identification of tree groups used by secondary cavity-nesting birds to simplify forest management in subtropical forests

In tropical and subtropical forest ecosystems,cavities formed by decay processes are a key but scarce resource for birds that nest and roost in them,which makes them a highly sensitive group to logging.The piedmont forest of northwestern Argentina is a complex ecosystem with 113 tree and 120 bird species.It has high logging pressure on the few,well-conserved forest remnants,complicating the delineation of sustainable management guidelines for each tree or bird species in a short time.Our objective was to reduce the complexity of subtropical forests by grouping tree species according to the characteristics used by secondary cavity-nesting birds(i.e.non excavators).In the piedmont forest,50 plots of 0.25 ha were sampled to record cavity trees and cavity characteristics.These were then used in a cluster analysis to form tree groups.Additionally,cavities were searched to identify the bird species using the decay-formed cavities.A total of 187 cavity trees,comprising 23 tree species,were recorded,and these formed four tree groups or clusters.We recorded 86 cavities that were used by secondary cavitynesting bird species.The four tree groups were unequally used by secondary cavity nesters.The tree group that included valuable timber species(Myroxylon peruiferum,Anadenanthera colubrina and Calycophyllum multiflorum)and had the greatest cavity availability represented 71%of total cavity use.Another tree group with valuable timber species(Cedrela balansae and Amburana cearensis),measured>73 cm DBH and>21 m tall,had cavity entrances>0.10 cm2,and contributed 14%of all cavity use by birds.A third group had no highly economically valuable tree species,and included the snag category(i.e.standing dead trees)as well as a 15%of cavity use.The fourth tree group had a DBH<0.40 cm,only one highly economically valuable tree species(Cordia trichotoma),and supported no cavity use.The clustering of subtropical trees can reduce the complexity of these forests,hence easing their management by focusing on those groups with tree species showing similar characteristics and providing suitable nesting sites for secondary cavity-nesting birds.

Habitat-dependent breeding biology of the Blue Tit(Cyanistes caeruleus)across a continuous and heterogeneous Mediterranean woodland

Mediterranean woodland environments are characterised by high spatial and temporal heterogeneity,which means the inhabiting species face a wide variety of selective pressures.Species may respond differently to habitat heterogeneity and so distinct eco-evolutionary scenarios may be responsible for the inter-habitat variability in reproductive strategies observed in certain species.The inter-forest variability of some reproductive traits in passerines has been examined by comparing forest patches or separated fragments.However,there is still little information regarding how such highly mobile animals adjust their breeding performance across continuous and heterogeneous woodlands.Here we studied the reproductive performance of a population of Blue Tits(Cyanistes caeruleus) in an area of continuous Mediterranean woodland that included two mountain slopes and four different types of forest,ranging from deciduous oak forests to perennial non-oak forests.We studied the habitat heterogeneity and inter-forest phenotypic variation in terms of reproductive performance and adult and nestling biometry,besides also exploring the effects of ectoparasites on Blue Tit reproduction.Eggs were laid earliest in deciduous Pyrenean Oak(Quercus pyrenaica) forests,while clutch size and the number of fledglings were highest in the humid Pyrenean Oak forest,which had the greatest tree coverage and most humid climate,and lowest in the coniferous Scots Pine(Pinus sylvestris) forest.There were no inter-forest differences in hatching(percentage of nests with at least one egg hatched) and fledging(percentage of nests in which at least one nestling fledged)success.Similarly,there were no inter-forest differences in adult and nestling biometry,but adults that raised more fledglings had a lower body mass,while males whose females laid larger clutches had smaller tarsi.Most ectoparasites did not affect Blue Tit reproduction,although Culicoides had a negative impact on nestling body mass.These results suggest that Blue Tits can adjust their reproductive effort to the forest where they breed even across a very small spatial scale.Different eco-evolutionary scenarios,such as phenotypic plasticity or genetic structuring and local adaptation,might explain the phenotypic differentiation in the reproductive strategies observed over small areas in woodlands.

Factors determining the occupancy of nest-boxes by Great Tits(Parus major)in eucalypt plantations

Providing nest-boxes as surrogate tree cavities can be of great importance to increase the breeding populations of cavity-nesting birds in managed forests.However,the exact placement of nest-boxes should be taken into consideration to enhance their occupancy according to species-specific preferences.In this study,we investigated which factors can better predict nest-box occupancy by the Great Tit(Parus major)in eucalypt plantations.We used generalised linear mixed-effects models to analyse the influence of topography,nest-box positioning,vegetation cover and landscape variables on three-year occupancy records from 80 newly provided nest-boxes.Non-random patterns of nest-box occupancy were found with respect to all categories except topography.Results suggest that Great Tits prefer to occupy high-placed nest-boxes,close to areas that can provide them with supplementary resources either within or in the vicinity of the stand(i.e.,trees other than eucalypts,riparian vegetation,and large patches of adjacent habitats).Overall,this study provides important recommendations for nest-box placement and spatial distribution in managed forests and enhances the potential of nest-box interventions as a biodiversity offset and management tool.

Plastering mud around the entrance hole affects the estimation of threat levels from nest predators in Eurasian Nuthatches

Background:For cavity-nesting birds,the nest entrance plays an important role in preventing predators from accessing nests.Several species of nuthatches use mud to narrow the entrance of cavities.In theory,the smaller the entrance hole size,the more effective it is against predators;however,few studies have tested whether narrowing the entrance hole size can affect the estimation of threat levels from nest predators in cavity-nesting birds.Methods:Using dummy experiments,we tested whether Eurasian Nuthatches(Sitta europaea,narrow the entrance hole of cavities)and Cinereous Tits(Parus cinereus,do not narrow the entrance hole,as a control)perform different nest defence behaviours against Common Chipmunks(Tamias sibiricus,small nest predator)and Red Squirrels(Sciurus vulgaris,larger nest predator).Results:Both nuthatches and tits exhibited stronger response behaviours(high dummy response scores)against chipmunks than against squirrels.Compared with tits,nuthatches exhibited more aggressive behaviours to chipmunks,but their responses to squirrels were similar.Conclusions:Nest defence behaviours of nuthatches to chipmunks differed from tits,and the results suggested that nuthatches might estimate threat levels of nest predators according to their narrowed entrance-hole size.

A field guide for aging passerine nestlings using growth data and predictive modeling

Background:Accurate nestling age is valuable for studies on nesting strategies,productivity,and impacts on repro-ductive success.Most aging guides consist of descriptions and photographs that are time consuming to read and subjective to interpret.The Western Bluebird(Sialia mexicana)is a secondary cavity-nesting passerine that nests in coniferous and open deciduous forests.Nest box programs for cavity-nesting species have provided suitable nesting locations and opportunities for data collection on nestling growth and development.Methods:We developed models for predicting the age of Western Bluebird nestlings from morphometric meas-urements using model training and validation.These were developed for mass,tarsus,and two different culmen measurements.Results:Our models were accurate to within less than a day,and each model worked best for a specific age range.The mass and tarsus models can be used to estimate the ages of Western Bluebird nestlings 0-10 days old and were accurate to within 0.5 days for mass and 0.7 days for tarsus.The culmen models can be used to estimate ages of nest-lings 0-15 days old and were also accurate to within less than a day.The daily mean,minimum,and maximum values of each morphometric measurement are provided and can be used in the field for accurate nestling age estimations in real time.Conclusions:The model training and validation procedures used here demonstrate that this method can create aging models that are highly accurate.The methods can be applied to any passerine species provided sufficient nest-ling morphometric data are available.

A global review of the ecological significance of symbiotic associations between birds and fungi

Symbiotic associations between mammals and fungi have been well documented and are widely regarded as vital to ecosystem functions around the world.Symbioses between birds and fungi are also ecologically vital but have been far less thoroughly studied.This manuscript is the first to review a wide range of symbiotic associations between birds and fungi.We compile the largest list to date of bird species reported to eat fungi(54 bird species in 27 families)and follow up with a discussion of these symbioses and suggestions for how future studies can determine the prevalence of associations between birds and fungi.We review the importance of fungi for cavity-excavating birds and show that at least 30 bird species in three families form varying levels of associations with fungi for cavity excavation.We also review the use of fungal rhizomorphs in nest construction and show that 176 bird species in 37 families use fungal material in their nests.All of these interactions have wide-reaching ecosystem implications,particularly in regard to fungal dispersal and biogeography,plant health,ecosystem function,bird nutrition/fitness and bird behaviour.