Effects of Sitka spruce masting on phenology and demography of siskins Spinus spinus

Masting behaviour of Sitka spruce Picea sitchensis may influence Eurasian siskin Spinus spinus breeding ecology as breeding siskins specialize on spruce seeds. We caught siskins and other small passerines over 16 years using mist nets adjacent to large plantations of mature Sitka spruce. We sexed, aged, measured and weighed the birds and collected feather samples from fledglings to measure nitrogen and carbon stable isotope ratios. Siskins departed in late summer, and returned, and bred earlier in years of higher cone abundance. Nitrogen and carbon isotopes indicated that siskins fed their chicks on Sitka spruce seeds in most years, and more so in years of high cone production. More siskins were caught following heavy rainfall, when the cones had closed, encouraging the birds to seek alternative food sources. Fledglings were not heavier or larger in years with higher cone crops but were more numerous. However, the age ratio of siskins caught the following year was unaffected by cone crop. Given their reliance on Sitka spruce seeds, climate change may have a major impact on siskin numbers by altering the availability of Sitka spruce seeds, either through changes in masting patterns or cone opening, or due to climate-related changes in forestry practices. Siskins represent a valuable study system to conservation ecology, where a native species is ecologically reliant on introduced taxa

Proof of concept evidence that stable isotopes of carbon, nitrogen and sulfur may identify individual kittiwakes breeding in different colonies

Rationale: Carbon, nitrogen and sulphur stable isotopes in feathers grown by seabirds while breeding reflect the local isoscape and diet in the vicinity of the colony, so may make it possible to discriminate individual birds from different colonies. Methods: Black-legged kittiwake Rissa tridactyla inner primary feathers from two colonies about 350 km apart in the North Sea were used to test whether δ13C, δ15N and δ34S differed between individuals from the two colonies. Feather tips cut from breeding birds caught at nests were compared with tips of moulted feathers (grown 1 year earlier) found on the ground. Results: Isotopic compositions showed no overlap between the two colonies in δ13C, δ15N or δ34S in tips of newly-grown feathers sampled from breeding adult kittiwakes. There was some overlap in δ13C, δ15N and δ34S from moulted feathers, but discriminant analysis allowed >90% of individuals to be assigned to their colony. In five of six comparisons, mean isotopic compositions were the same in new and moulted feathers but not for δ34S at one of the two colonies. Conclusions: This study has demonstrated for the first time that stable isotopes in inner primary feathers of kittiwakes can allow accurate identification of the breeding colony of individual birds from two different colonies within the North Sea. Further research is required to determine if this method can be applied with greater spatial resolution and to a larger number of colonies

Ixodes ricinus parasitism of birds increases at higher winter temperatures

Increasing winter temperatures are expected to cause seasonal activity of Ixodes ricinus ticks to extend further into the winter. We caught birds during winter months (November to February) at a site in the west of Scotland over a period of 24 years (1993–1994 to 2016–2017) to quantify numbers of attached I. ricinus and to relate these to monthly mean temperature. No adult ticks were found on any of the 21,731 bird captures, but 946 larvae and nymphs were found, with ticks present in all winter months, on 16 different species of bird hosts. All ticks identified to species were I. ricinus. I. ricinus are now active throughout the year in this area providing temperature permits. No I. ricinus were present in seven out of eight months when the mean temperature was below 3.5º C. Numbers of I. ricinus attached to birds increased rapidly with mean monthly temperatures above 7º C. Winter temperatures in Scotland have been above the long‐term average in most years in the last two decades, and this is likely to increase risk of tick‐borne disease

Data from: Long-term declines in winter body mass of tits throughout Britain and Ireland correlate with climate change

1. The optimum body mass of passerine birds typically represents a trade-off between starvation risk, which promotes fat gain, and predation pressure, which promotes fat loss to maintain manoeuvrability. Changes in ecological factors that affect either of these variables will therefore change the optimum body masses of populations of passerine birds. 2. This study sought to identify and quantify the effects of changing temperatures and predation pressures on the body masses and wing lengths of populations of passerine birds throughout Britain and Ireland over the last 50 years. 3. We analysed over 900,000 individual measurements of body mass and wing length of blue tits Cyanistes caeruleus, coal tits Periparus ater, and great tits Parus major collected by licenced bird ringers throughout Britain and Ireland from 1965 to 2017, and correlated these with publicly available temperature data and published, UK-wide data on the abundance of a key predator, the sparrowhawk Accipiter nisus. 4. We found highly significant, long-term, UK-wide decreases in winter body masses of adults and juveniles of all three species. We also found highly significant negative correlations between winter body mass and winter temperature, and between winter body mass and sparrowhawk abundance. Independent of these effects, body mass further correlated negatively with calendar year, suggesting that less well understood dynamic factors, such as supplementary feeding levels, may play a major role in determining population optimum body masses. Wing lengths of these birds also decreased, suggesting a hitherto unobserved large-scale evolutionary adjustment of wing loading to the lower body mass. 5. These findings provide crucial evidence of the ways in which species are adapting to climate change and other anthropogenic factors throughout Britain and Ireland. Such processes are likely to have widespread implications as the equilibria controlling evolutionary optima in species worldwide are upset by rapid, anthropogenic ecological changes

Quantifying the History of Building Stone Use in a Heritage City: Cambridge, UK, 1040–2020

Building stone use through time in Cambridge is reassessed based on a new field survey of most significant buildings within the city boundary. Included in the survey is stone external to buildings, as walling or dressings, but omitting paving and most roofing. Stone provenance is identified to a quarry or quarry group where possible. Stone location is specified by grid reference and as a named component of each building. The date of each building project is extracted from documentary evidence if available. The volume of stone used in each project is estimated from whether it forms walls or dressings or both, and over what proportion of the host building. Assigning stone types to a single quarry, mostly in a laterally and vertically heterogeneous shallow-marine Jurassic carbonate sequence, involves the use of ‘type locations’—buildings with documented evidence of stone source and construction date. Field-scale identification criteria are essential to complement museum reference samples and microscopic petrography. The new database of stone and brick includes over 1300 records, about three times more than compiled from previous studies. This semi-quantitative approach to stone use yields pie charts of relative volumes of stone types, scatter plots of first use of each quarry’s stone against its distance from Cambridge, and histograms of the volume of each stone type through time. These results inform discussion of geological, locational, and societal influences on the sequence of stone use. The methodology used in the Cambridge study should prove useful in other heritage towns and cities

The jigsaw model: A biogeographic model that partitions habitat heterogeneity from area

Species–area models now frequently include habitat heterogeneity. These models often fit real-world data better than those that exclude this factor. However, such models usually link the effects of habitat heterogeneity and study area. Critically, we show that difficulties in quantifying habitat heterogeneity within these models can lead to distortions of the apparent effect of area on species richness. Here, we derive a model that minimises these distortions by partitioning the influence of habitat heterogeneity from that of area, without compromising ease of application. This ‘jigsaw model’ achieves this by assuming that different habitats within an area can support similar numbers of species. We compare the behaviour of this model to that of existing models of similar complexity using both simulated island ecosystems and 40 published empirical datasets. The effects of habitat heterogeneity and area on species richness vary independently in our simulations, and these independent effects are recovered by the jigsaw model. This flexibility, however, is not present when the same data are analysed using other models of similar complexity. When applied to real-world data, the jigsaw model demonstrates that the relative importance of area and habitat heterogeneity varies depending on the study system. The jigsaw model provides the best fit to real-world data (according to AICc) of all tested models in logarithmic form, and the second best fit, after the choros model, in power-law form. Our results demonstrate the importance of partitioning the effects of habitat heterogeneity and area on species richness in biogeographic models. The jigsaw model is a simple but powerful tool for such partitioning. It has the potential to elucidate the underlying drivers of species richness patterns, and to be used as a tool in biological conservation projects, where data are often incomplete