Nicholas I. Wilkinson

Age structure and history of stand types of Pinus sylvestris in Abernethy Forest, Scotland

Abstract Abernethy Forest comprises the largest area of semi-natural (native) pinewood in Scotland. It also has plantations of various ages. This study describes the sizes and ages of Scots pines (Pinus sylvestris L.) in the main stand types as a basis for future management, which aims to develop woodland of natural character. The interpretation of the current age structure is based on historical records of past management [commercial forestry, crofting (subsistence farming) and red deer Cervus elaphus (L.) management for sport shooting] and fires. The main plantation stand types had trees with median ages ranging from 20 to 67 years. The main stand types of semi-natural pinewood (old open, high crown and bog woodland) had median ages of 149, 120 and 126 years and peaks at 121–130, 111–120 and 141–150 years, respectively. The establishment of trees in these stands largely coincided with the removal of crofters and their livestock in 1869, when the upper forest was designated as a sporting estate. This probably allowed a pulse of tree regeneration, before the growing red deer population and pasturing of sheep and cattle inhibited further regeneration through much of the twentieth century. After 1988, sheep and cattle were removed and the number of red deer was reduced, allowing previously suppressed pine saplings to grow. Exploitation for timber over the past 400 years has meant that few trees are over 200 years old. This contrasts with natural Scots pine forests in Fennoscandia where trees typically attain this age, and where the structure is often determined by fire.

Effect of cereal harvesting method on a recent population decline of Corn Buntings Emberiza calandra on the Western Isles of Scotland

Capsule Population decline since 1995 is associated with the harvesting of cereals as arable silage. Aim To survey Corn Bunting populations on the Western Isles and test whether population changes since 1995 are associated with change in cereal harvesting methods. Methods Twelve areas of machair on the Uists and Benbecula were re-surveyed in 2002, after previous surveys in 1983 and 1995. These and other areas of suitable habitat on these islands, plus Berneray, Baleshare, Vallay, Barra and Vatersay, were surveyed in 2003–05 to provide a breeding population estimate for the Western Isles. Cereal strips in the 12 core survey areas were mapped in 2002 and the timing and method of harvesting of each was recorded. Cattle-feeding stands in 24 crofting townships were visited in March 2003 to record the type of fodder available, measure grain abundance and ripeness in fodder samples, and record foraging Corn Buntings. Experimental trials tested whether Corn Buntings selected fodder with riper grain. Results The Western Isles Corn Bunting population was estimated at 117 occupied territories in 2005, a decline of 17% since 2002/03, and of at least 62% since 1995. Population decline was greater in areas with higher proportions of the cereal area harvested as arable silage. Arable silage contained fewer and less-ripe grains than traditionally harvested cereal, and was less likely to attract feeding Corn Buntings. Corn Buntings preferred to feed on silage containing riper grain. Conclusions The remaining Corn Bunting population of the Western Isles is declining rapidly, probably because of reduction in winter grain supply caused by change from traditional reaper-binder harvesting and stacking of fully ripe cereals to harvesting the crop as unripe or partially ripe arable silage. Management change to restore a supply of ripe grain over winter is likely to be essential if this population decline is to be halted and reversed.

Factors influencing the small-scale distribution of House Sparrows Passer domesticus in a suburban environment

Capsule Suburban House Sparrows prefer gardens with native bushes but show no detectable response to garden insecticide use. Aims To identify the factors that influence House Sparrow distribution among suburban gardens. Methods Bicycle transects were used to survey House Sparrows in front gardens in suburban Oxford in the spring of 2004. A subset of 498 gardens was selected comprising all those where sparrows were found and an equal number of randomly selected sparrow-free gardens. In each of these gardens the density of bushes and the proportion of native bushes were recorded and insecticide use and house age were sampled by questionnaire. Binary logistic regression was used to compare these variables with the presence or absence of House Sparrows. A larger scale analysis was also conducted comparing 25 squares, each 250 m2. The density of House Sparrows in the total area of front gardens in these squares was compared to the area of green space within the square, its distance from the city edge and encounter rates of corvids on the cycle transects. Results House Sparrows show a preference for gardens with native bushes. They also prefer gardens with a higher overall density of bushes but appear to make no distinction based on insecticide use or house age. There is no evidence that green space, distance from the city edge or density of corvids affect sparrow numbers at a larger spatial scale. Conclusion House Sparrows might benefit from planting of native bushes but not apparently from a reduction in garden insecticide use. The preference for native vegetation most likely reflects the associated abundance of insect food, which is required by the growing chicks. Further investigation of the habits of House Sparrows in the breeding season may shed light on the causes of the recent decline of the species.

Breeding ecology of Twite Carduelis flavirostris in a crofting landscape

Capsule Twite nested close to and exploited rich seed sources on machair, and had high breeding productivity relative to other studies of Carduelis finches. Aims To test whether Twite nesting distribution, breeding phenology and success, foraging habitat selection, and nestling diet in a high density population on the Western Isles of Scotland are associated with the habitats and food sources provided by agricultural management of machair habitats. Methods Breeding season transect surveys and intensive nest finding were used to quantify the habitat associations, distribution, phenology, nest success and nestling diet of breeding Twite on study areas in the Western Isles of Scotland. Individual colour‐ringing was used to estimate the number of breeding attempts being made by individual adults. Results Nesting Twite were strongly associated with moorland edge habitats adjacent to machair, with most nests in Heather or shelter‐belt conifers, and the birds fed almost exclusively on seed sources characteristic of machair grassland and fallows rather than moorland. Nesting success did not vary between habitats or study areas, although both clutch and brood sizes showed a mid‐season peak. Individual adults made up to three nesting attempts in one season, and overall breeding productivity was high relative to other recent studies of Carduelis finches, including studies of the declining Twite population in the English Pennines. Conclusion The maintenance of rich seed sources provided by the mix of low‐intensity arable and grassland management of the machair are likely to be essential to maintaining high Twite population density and indicate that management intervention to restore such seed sources in the habitats of declining populations should be a high priority.

Frequency of multiple brooding in Ring Ouzels, including first documented cases of triple brooding

Capsule The majority of female Ring Ouzels made two successful breeding attempts in a single season, but triple brooding was much less common.

The population status of Capercaillie Tetrao urogallus in Scotland during winter 2015–16

ABSTRACT Capsule: The population size of Western Capercaillie Tetrao urogallus in Scotland was estimated at 1114 individuals with 95% confidence intervals (CIs) of 805–1505. Aim: To produce an updated estimate of Capercaillie population size in Scotland, with improved precision from, but retaining comparability with, previous surveys. Methods: A random sample of 2 km long line transects was surveyed throughout the current range of the Capercaillie, during winter 2015–16, with sampling in three separate strata. Multi-covariate distance sampling was used to fit detection functions to the Capercaillie data, deriving national, regional and sex-specific estimates of density and abundance. Results: Across 741 transects, 136 Capercaillie were recorded in 120 separate encounters, giving rise to a population estimate of 1114 individuals (95% CIs: 805–1505). This estimate is 13% lower than that from the previous survey in 2009–10 but the difference is not statistically significant. Most of the population (83%) was estimated to occur in Strathspey, with much smaller numbers in the rest of the range. Conclusion: The Capercaillie population in Scotland remains at a critically low level. Further evidence of decline in edge of range subpopulations raises serious concern over the viability of Capercaillie in these areas, whereas numbers appear stable in the core of the range in Strathspey. The use of a revised survey design, with greater sampling in the core of the range, improved estimate precision.

The population status of breeding Twite Linaria flavirostris in the UK in 2013

ABSTRACT Capsule: The second national survey of Twite Linaria flavirostris estimated a UK breeding population of 7831 pairs (95% confidence limits: 5829–10 137) in 2013. Aims: To estimate the breeding population size of Twite in the UK and constituent countries and to calculate change since the 1999 survey. Methods: Counts of Twite were made on three visits between May and July across a stratified random sample of 1-km squares in England, Scotland and Wales. In Northern Ireland, a complete census was made of the known range and adjacent 1-km squares with suitable habitat. Field surveys involved walking line transects 200 m apart and, in suitable nesting habitat, making 5-minute stops at 100 m intervals to scan and listen for Twite. Results: The UK population of Twite was estimated at 7831 pairs (95% CL: 5829–10 137). This was 21% lower but not significantly different from the 1999 survey estimate. Scotland held 98% of the UK population (7640, 95% CL: 5629–9954). There were an estimated 164 pairs (95% CL: 76–297) in England, a significant decline of 72% from 1999. Estimated totals for Wales and Northern Ireland were 16 (95% CL: 10–24) and 18 pairs respectively. Conclusion: The second national survey suggests a moderate decline in the UK Twite population since 1999 but with considerable variation between countries. Further work is required to understand the drivers of population change across breeding populations.