Low incidence of leg and foot injuries in colour-ringed marsh tits Poecile palustris

Marking birds with individually identifiable metal leg-rings (bands) is a common research tool, and the additional use of plastic colour-rings has facilitated numerous studies of bird ecology, yet there is limited information for the impact of these methods on individuals and populations. Despite generally being considered to have a negligible effect upon birds, recent literature shows that leg rings can cause injuries to some passerines. This creates an ethical problem and may also bias research results by influencing individual behaviour and survival. The incidence of leg injuries was monitored on colour-ringed and unringed Marsh Tits over 12 years. The overall incidence of permanent injury did not differ between ringed and unringed birds, but six out of 404 colour-ringed birds (1.5%) carried a leg or foot injury, which was significantly greater than the background rate (0.2%) among 515 unringed birds. However, some injuries on ringed birds were temporary and/or may have been unrelated to the rings, although one fatality and two serious injuries were recorded, probably resulting from colour-rings becoming caught on thorns or other objects. Although ring-related injuries were very rare, it is recommended that ringers studying Marsh Tits try to minimise the number of rings on each leg

A nestbox trial for British marsh tits Poecile palustris

Two experimental nestbox trials were attempted, which aimed to maximise uptake by Marsh Tits in British woodland. Nestboxes which more closely approximated the dimensions of natural cavities were used more frequently than standard nestboxes, but the overall uptake was low. We conclude that nestboxes are an inefficient method of monitoring Marsh Tits, at least in the British context, and researchers should concentrate efforts on locating and monitoring natural nest sites

Habitat modelling and the ecology of the marsh tit (Poecile palustris).

Among British birds, a number of woodland specialists have undergone a serious population decline in recent decades, for reasons that are poorly understood. The Marsh Tit is one such species, experiencing a 71% decline in abundance between 1967 and 2009, and a 17% range contraction between 1968 and 1991. The factors driving this decline are uncertain, but hypotheses include a reduction in breeding success and annual survival, increased inter-specific competition, and deteriorating habitat quality. Despite recent work investigating some of these elements, knowledge of the Marsh Tit’s behaviour, landscape ecology and habitat selection remains incomplete, limiting the understanding of the species’ decline. This thesis provides additional key information on the ecology of the Marsh Tit with which to test and review leading hypotheses for the species’ decline. Using novel analytical methods, comprehensive high-resolution models of woodland habitat derived from airborne remote sensing were combined with extensive datasets of Marsh Tit territory and nest-site locations to describe habitat selection in unprecedented detail. Further fieldwork established the causes and frequency of breeding failure at the local population scale, and dispersal distances and success were quantified. Information from these studies was used to inform national-scale spatial analyses of habitat distribution in relation to the pattern of range contraction for the Marsh Tit and two other woodland bird species. The combined results indicate that Marsh Tits require extensive areas of mature woodland in order to accommodate large territories and short dispersal distances, with greatest selection for a woodland structure encompassing a tall, near-closed tree canopy and extensive understorey. The evidence suggests that nest-site competition, nest predation or deteriorating habitat quality have not driven the population decline. However, reduced connectivity between woodlands in the landscape, possibly due to hedgerow loss, may have interacted with increased mortality to precipitate population declines and local extinctions where habitat fragmentation was relatively high. The potential causes of increased mortality are discussed, along with priority areas for future research and the wider possible applications of remote sensing techniques in the field of woodland bird research

Nesting behaviour and breeding success of willow tits Poecile montanus in north-west England

The British Willow Tit Poecile montanus has undergone a substantial decline in abundance and a severe contraction in range since the 1970s, for reasons that are poorly understood. Breeding failure, due to nest-site competition and predation, has been suggested as a potential factor in the decline, but limited data exist for the nesting ecology and breeding productivity of the species in Britain. We studied a sample of 128 Willow Tit nests in a habitat mosaic of early successional woodland, scrub and wetland in a post-industrial landscape in north-west England, which is increasingly becoming a key refuge for the species in Britain. Results showed that nesting began in April, with standing deadwood of silver birch Betula pendula, common elder Sambucus nigra and black alder Alnus glutinosa being the most frequent nest sites, and the characteristics of nest sites are described. Daily survival rates and overall probability of nest survival are calculated, and details are given for the timing of breeding, clutch size, nestling survival and number of fledglings produced. Overall, 55% of nesting attempts were successful, although many first breeding attempts failed due to Willow Tits being evicted from their nest cavity by Blue Tits Cyanistes caeruleus, or nests being predated by Great Spotted Woodpeckers Dendrocopos major and, potentially, grey squirrels Sciurus carolinensis. Repeat breeding attempts were relatively more successful, but produced fewer fledglings on average. The results are discussed in the context of other studies of Willow Tits and some related species, and also the implications for the conservation of Willow Tits in Britain

Breeding success of the great tit Parus major in relation to attributes of natural nest cavities in a primeval forest

An overlap in attributes of nest cavities used by Great Tit Parus major across Eurasia suggests similar nest site preferences within the geographical range, although the drivers of these preferences are unclear. To determine whether preferred cavities provide conditions enhancing successful reproduction, we investigated the breeding performance of Great Tits in relation to tree cavity characteristics using data collected during 2008–2011 in primeval conditions (Białowieża National Park, Poland). Here, tree cavities are diverse and superabundant but nesting birds are at risk from a variety of predators. According to expectations, nest losses were high (60 % of Great Tit nests failed), mostly due to predation (69 % of nest failures). The risk of nest failure varied with nest cavity attributes. Compared to successful nests, failures were situated higher above the ground and placed closer to the cavity entrance. Very deep cavities with narrow entrances and strong livings walls provided effective protection against larger predators (e.g., martens, woodpeckers), unable to enter the cavity or pull out the contents. Yet, such holes were no barrier for the smallest predators (e.g., Forest Dormouse Dryomys nitedula), which were able to enter any Great Tit nest cavity and destroyed most of the nests. Avoiding small predators would give a selective advantage to the birds, but this seems hardly possible to achieve. We conclude that tree cavities preferred by the tits show a combination of properties which are a compromise for avoiding predation (the strongest selective pressure) and providing the minimum requirements (sufficient nest illumination, microclimate, protection against nest soaking) for development and growth of young

Winter habitat selection by marsh tits Poecile palustris in a British woodland

Capsule: Radio-tracking and remote sensing showed Marsh Tits selected for English Oak Quercus robur trees within large winter home-ranges. Aims: To investigate winter habitat selection by Marsh Tits in a British wood, testing for preferences in tree species and woodland structure. Methods: Thirteen Marsh Tits were radio-tracked during the winter, and home-ranges were derived. Lidar and hyperspectral data were used to compare the vegetation structure and tree species composition of entire home-ranges and the core areas of intensive use within. Instantaneous sampling observations provided further information for tree species utilization. Results: The mean home-range was very large (39 ha, n=13). There were no significant differences in mean tree height, canopy closure, understorey height, or shrub volume between full home-ranges and the core areas of use. Core areas contained a significantly greater proportion of English Oak relative to availability in the full home-ranges. Instantaneous sampling confirmed that English Oak was used significantly more than other trees. Conclusion: Selection for English Oak during winter contrasted with previous studies of breeding territories, indicating that habitat usage varies seasonally and demonstrating the need for habitat selection studies throughout the year. Large home-ranges help to explain the Marsh Tit’s sensitivity to habitat fragmentation

Separating British marsh tits Poecile palustris and willow tits P. montana using a new feature trialled in an online survey

Confident separation of Marsh Tits and Willow Tits remains a challenge in Britain due to the similar appearance of the local races of both species. Several criteria are available to assist the identification of birds in the hand, but none is completely diagnostic and most are invalid for young juvenile birds. Due to the continued decline in abundance of both species, however, it is becoming increasingly difficult to trial new identification criteria in the field, as very few ringers are catching sufficient numbers of either species. This paper describes the results of an online survey that was used to test a proposed new identification feature for separating the two species, based on differences in the pattern of colour contrast on the greater covert feathers. The online survey was effective in recruiting a sufficient sample of ringers of varying experience, who were asked to identify images of Marsh Tits or Willow Tits based only on features of the greater coverts that were demonstrated using training images. On average, each ringer correctly identified 82% of the 18 images, and each image was correctly identified by an average 84% of the 140 ringers. The pattern of the greater coverts is therefore recommended as an additional, complementary criterion for separating Marsh Tits from Willow Tits. Online surveys are also recommended as an efficient platform for the trialling of identification features among the ringing community

Understanding potential sources of bias and error in the biometric sexing of birds

Biometrics, particularly wing length, are commonly used to assign the sex of many birds in species where the plumage is similar for males and females. Virtually all species show some measurement overlap between the sexes, however, and measurement error can add further uncertainty into data sets. This can result in individuals being misclassified as the wrong sex and introducing bias into subsequent analyses, particularly if the life histories of misclassified birds differ from those of others. We used the Marsh Tit Poecile palustris as a case study to examine potential sources of error and bias when assigning sex based on wing length. There was no evidence for a heritability of wing lengths that could result in localised populations of atypical size via a ‘founder effect’, which would otherwise undermine biometric sexing. Additionally, potentially misclassified birds did not differ from others in how long they persisted in the local population, so avoiding any potential bias of misclassification in demographic analyses. Compared to Marsh Tit data collected during intensive studies, the national data set pooled from contributors across Britain showed much greater variation in wing lengths, resulting from wider variation in the accuracy of measurement and recording. This variation in pooled data can have implications for analyses, and we discuss the importance of data quality in ringing schemes

Microclimate in tree cavities and nest-boxes: implications for hole-nesting birds

The provision of nest-boxes is widely used as a conservation intervention to increase the availability of cavities for hole-nesting birds, particularly in managed forests, but it is uncertain whether nest-boxes are an appropriate substitute for tree cavities. Tree cavities and nest-boxes may differ in many aspects, including microclimate, but there are few data with which to examine this. We measured the air temperature and relative humidity in vacant tree cavities previously used by breeding marsh tits Poecile palustris (a non-excavating forest passerine) and in nest-boxes provided for this species that had similar dimensions to natural nest sites, and we compared values from both with ambient conditions. We examined how tree cavity characteristics influenced microclimate and if similar conditions were replicated in nest-boxes. Tree cavities, particularly those in thicker parts of trees, were more efficient thermal insulators, with temperature extremes dampened to a greater extent relative to ambient values. In contrast, the nest-boxes provided poor insulation with negligible buffering against ambient temperatures. Mean daily relative humidity was high (on average c. 90%) in tree cavities, which all had walls of living wood, and this averaged 24% higher than in nest-boxes at comparable ambient conditions (mean humidity 76–78%). These results support previous studies that incorporated various types of tree cavities and nest-boxes, indicating that the environment within nest-boxes differs significantly from that of tree cavities. We conclude that providing nest-boxes may affect microclimatic conditions available for cavity-users, which may have ecological implications for nesting birds

Multi-scale settlement patterns of a migratory songbird in a European primeval forest

The drivers of animal settlement are core topics in ecology. Studies from primaeval habitats provide valuable but rare insights into natural settlement behaviour, where species are unconstrained by habitat fragmentation and modification. We examined whether territorial male songbirds (wood warblers Phylloscopus sibilatrix) exhibited clustered distributions when settling in extensive primaeval forest. We tested whether settlement patterns were consistent between years, the influence of habitat preference and the spatial extent of these processes. Remote sensing (airborne LiDAR and satellite multi-spectral) and field survey data were combined to investigate settlement at the landscape (tens of km2), plot (46–200 ha) and microhabitat (20 m diameter) scales, by sampling across 5.9 × 4.5 km of the Białowieża National Park (Poland) during 2018–2019. We assessed bird distribution patterns using nearest neighbour analyses, and habitat preference with generalized linear mixed models. Variation in bird density between plots and years was suggestive of large-scale clustering at the landscape scale. At the local plot scale, any clustering was masked by territoriality, with birds appearing dispersed or randomly distributed. At the microhabitat scale within territories, birds preferred a tall, closed canopy forest structure and avoided a dense herb layer of wild garlic patches. Settlement appeared unconstrained by the availability of preferred habitat at the plot scale, which remained unsaturated. Wood warbler settlement apparently involved hierarchical decisions at multiple spatial scales, compatible with potential social attraction, territoriality, habitat preference or predator avoidance. Selecting an appropriate scale of analysis is an important consideration when assessing the clustering of territorial species