Population differences in the length, early-life dynamics, and heritability of telomeres among European pied flycatchers

Telomere length and shortening rate are increasingly used as biomarkers for long-term costs in ecological and evolutionary studies because of their relationships with survival and fitness. Telomere length can be heritable, but both early-life conditions and later-life stressors can create variation in telomere shortening rate. Studies on between-population telomere length and dynamics are mostly lacking, despite the expectation that populations exposed to varying environmental constraints would present divergent telomere length patterns. Pied flycatcher (Ficedula hypoleuca) is a passerine bird spending the non-breeding period in sub-Saharan Africa but breeding across Eurasia (from Spain to western Siberia). Populations show marked differences in migration distance, genetics, breeding parameters, and egg components. We studied the large-scale variation of telomere length, early-life dynamics and heritability in the pied flycatcher by comparing six European populations across a north-south gradient (Finland, Estonia, England and Spain). There were clear population differences in telomere length, with English birds having the longest telomeres, followed by Spanish and lastly by Estonian and Finnish birds. Early-life telomere shortening rate tended to vary between populations, and faster nestling growth affected telomeres more negatively in northern than southern populations. The heritability of telomere length was moderate (h2 = 0.34 - 0.40), with stronger heritability to paternal than maternal telomere length. There was also evidence indicating that the level of paternal heritability could differ between populations. While the sources of between-population differences in telomere-related biology remain to be identified (i.e. genetics, environmental factors), our study illustrates the need to expand telomere studies at the between-population level.

Territory-level temperature influences settlement decisions, breeding phenology and productivity in three forest passerine birds

Temperature is a key determinant of breeding phenology in temperate zone birds, with increasing spring temperature across years or large geographic gradients known to advance timing of breeding. It is less well understood how localised, territory-scale temperature variations effect territory occupation, breeding phenology and productivity, primarily due to a lack of fine-scale temperature data.We examine the influence of temperature at the territory-scale, and its interaction with mean annual temperature, on territory selection and breeding outcomes of three co-occurring forest passerine bird species; two long-distance migrants (pied flycatcher Ficedula hypoleuca and wood warbler Phylloscopus sibilatrix) and one resident (blue tit Cyanistes caeruleus); all species dependent on seasonal invertebrate food for reproductive success.Spring temperature was recorded at intersections of a 150m2 grid encompassing 417 ha of forest in South-West England 2015-18, with temperature across the study area interpolated from this point data. Breeding phenology and productivity from 672 nests across the three species was quantified, and general linear models used to examine the influence of territory temperature on breeding phenology and productivity.All three species exhibited significant trends in reproductive traits associated with territory-scale temperature. Pied flycatchers settled in cooler territories first, where they raised more fledglings. Blue tits laid larger clutches in warmer territories in warm years and always laid earlier at warmer territories irrespective of annual mean temperature. Contrastingly, pied flycatcher and wood warbler breeding phenology was earlier at warmer territories in cool years and cooler territories in warm years, with wood warbler clutch size responding similarly to this interaction. Greater previous breeding experience and increased territory quality also predicted earlier breeding phenology and higher productivity for pied flycatchers.Our results show that local-scale spatial variation in temperature is associated with spatial variation in territory occupancy, breeding phenology and productivity in forest passerines. We suggest that the two migrant species may be best synchronised with their prey requirements in cooler years at a local population level while resident blue tits match local phenology at lower trophic levels across all years, potentially advantageous under warmer predicted climate change scenarios.

Does nestbox type significantly alter the ectoparasitic load and breeding success in the nests of secondary-cavity-nesting passerines, at Nagshead, Forest of Dean?

This research aims to find if nestbox type causes a significant difference in the ectoparasite load and breeding success rate in the nests for four co-occurring secondary cavity nesting passerines, breeding in nestboxes at Nagshead Nature Reserve, Forest of Dean. The different nestbox types used in this study are old and new standard wooden nestboxes and deep nestboxes, which are designed to reduced predation. Nests were taken from nestboxes used by Blue Tit (Cyanistes caeruleus), Great Tit (Parus major), Nuthatch (Sitta Europaea) and Pied Flycatcher (Ficedula hypoleuca) by Nestbox Species Surveyors at the end of the 2019 breeding season, and later dissected to determine ectoparasite abundance and nest composition. Nest data collected by Nestbox Species Surveyors was used to calculate the breeding success rate. Population of woodland birds in 2018 was found to be overall 29% than in 1970. Deforestation and habitat management are causes in the reduction of nesting sites available for woodland bird species. Pine Martens (Martes martes), a known predator to secondary cavity nesting birds, were reintroduced into the Forest of Dean in September 2019. Individuals using nestboxes are at a potential increased risk of predation as nestboxes are accessible to Pine Martens. The abundance of adult Hen Fleas and Blowfly pupae in deep nestboxes was found to be significantly higher compared to the nestbox types. Nuthatch nests were found to have the highest mean abundance of adult Hen Fleas, while Pied Flycatcher nests had the highest mean abundance of Blowfly pupae, compared to the other species. Leaves as a nest material were found to have a significant influence and negative correlation with both ectoparasites mentioned. Breeding success rate in standard new boxes was significantly lower than the other nestbox types, with no significant difference occurring between deep and standard old nestboxes. Breeding success in Nuthatch nests were found to be significantly lower than the other avian study species potential linking the increased abundance of adult Hen Fleas previously found. Leaves were found to be significantly influencing and positively correlating with breeding success. These findings add to the data and knowledge about the difference in ectoparasite load and breeding success between nestbox types and the secondary cavity nest passerines, which use these nestboxes. This study also opens up potential for recommended future studies to be carried out at Nagshead.

Breeding biology and long-term population dynamics of the Pied Flycatcher Ficedula hypoleuca in Skibotn, Northern Norway

The breeding biology and population dynamics of the Pied Flycatcher Ficedula hypoleuca in pine, mixed and deciduous forests in Skibotn, Northern Norway (69°20’N, 20°20’E), was studied during 33 years (1987–2019; in total 1775 completed first clutches). It was a period during which summer temperatures remained relatively stable, but late spring (May) temperatures tended to become warmer. The number of breeding pairs declined over the study period but varied less than in populations living in more harsh subalpine environments. In spite of the northern location, females started to lay eggs in a relatively late phenological phase of the environment and in relatively warm weather. The date of birch leafing and the date of egg-laying advanced during the study period, and they correlated with each other. Mean clutch size was 6.4 eggs, and mean number of fledglings/nest 4.6. Date of egg-laying was earlier and clutch size larger in deciduous forests than in pine and mixed forests, but this did not translate into better fledgling productivity. The main causes of nesting failure were predation by small mustelids and starvation in warm and dry summers. However, in the long run the population seemed to be able to maintain itself without immigration, i.e., act as a source population. The possibility that during warm climate periods of the past, breeding biology and population dynamics of Pied Flycatchers over large geographical areas might have resembled those in Skibotn is discussed.