Chas A. Holt

National and regional patterns of habitat association with foraging Barn Swallows Hirundo rustica in the UK

Capsule Barn Swallows showed a consistent association with cattle across the UK, but certain landscape features, particularly mixed field types and tall trees, were also important. Aim To provide nationally representative data on habitat selection in foraging Barn Swallows. Method Observers carried out four timed point counts within an allocated 2-km square(s). Point counts were at least 500 m apart and considered as independent sample points. Each point count covered 100 m radius and was visited twice during the summer. An index of foraging activity was derived from the number of foraging passes made by Barn Swallows within ten minutes. The maximum count of Swallows present was also recorded. Habitat data included the presence or absence of landscape features and buildings and the proportion of area covered by particular crop and boundary types within the 100 m count radius. Results Cattle were the single most important and most consistent variable associated with foraging Barn Swallows, in every UK region. Horses were also important in the southeast. Grassland was only important if livestock were present. Foraging pass rates were higher where count circles contained a mixture of grass and arable fields rather than just one or the other. There was a general positive relationship between foraging pass rates and the presence of tall trees in boundaries, and this was significant in the arable eastern region of the UK, where their relative importance of concentrating prey may be more acute. Conclusion Historical changes in the distribution and availability of habitat features associated with foraging Barn Swallows are consistent with regional differences in population change for this species in the UK. These patterns of association are discussed in terms of changes in land use, the widespread loss of mixed farming and simplifications to landscape complexity.

DEER REDUCE HABITAT QUALITY FOR A WOODLAND SONGBIRD: EVIDENCE FROM SETTLEMENT PATTERNS, DEMOGRAPHIC PARAMETERS, AND BODY CONDITION

ABSTRACT. Understanding avian responses to ungulate-induced habitat modification is important because deer populations are increasing across much of temperate Europe and North America. Our experimental study examined whether habitat quality for Blackcaps (Sylvia atricapilla) in young woodland in eastern England was affected by deer, by comparing Blackcap behavior, abundance, and condition between paired plots (half of each pair protected from deer). The vegetation in each pair of plots was the same age. The Blackcap is an ideal model species for testing effects of deer on avian habitat quality because it is dependent on dense understory vegetation and is abundant throughout much of Europe. We compared timing of settlement, abundance, age structure (second-year vs. after-second-year), and phenotypic quality (measured as a body condition index, body mass divided by tarsus length) between experimental and control plots. We used point counts to examine Blackcap distribution, and standardized mist netting to collect demographic and biometric data. Incidence of singing Blackcaps was higher in nonbrowsed than in browsed plots, and singing males were recorded in nonbrowsed plots earlier in the season, indicating earlier and preferential territory establishment. Most Blackcaps, both males and females, were captured in vegetation prior to canopy closure (2–4 years of regrowth). Body condition was superior for male Blackcaps captured in nonbrowsed plots; for second-year males this was most marked in vegetation prior to canopy closure. We conclude that deer browsing in young woodland can alter habitat quality for understory-dependent species, with potential consequences for individual fitness and population productivity beyond the more obvious effects on population density.

Habitat use by Nightingales in a scrub–woodland mosaic in central England

SUMMARY Capsule Nightingales Luscinia megarhynchos with song territories in scrub vegetation also used adjacent woodland. Aims To examine spatial use by Nightingales of vegetation mosaics and associated selection of vegetation height classes. Methods We examined habitat selection by male Nightingales through territory mapping and radiotracking within a mosaic of dry scrub and woodland adjacent to water-filled gravel pits in eastern England. Results Fourteen song territories were exclusively in scrub, 2 were exclusively in woodland, and 13 comprised both habitat types. Densities were greatest in scrub vegetation of 3–5 m height. Best-supported models for territory density indicated the importance of considering optimal vegetation height within management prescriptions. Despite song territories being in scrub, kernel home-ranges of all radiotracked Nightingales contained areas of mature trees. Birds also spent more time there than expected based on availability of woodland within kernels. Conclusions Habitat quality has been implicated in the decline of Nightingales in lowland woodland in Britain (and an associated increase in the proportion found in scrub). Our results indicate that woodland habitat characteristics provide resources for Nightingales with song territories located in dry scrub and may be a factor in territory establishment, and are therefore relevant for conservation practitioners at such sites.

Do field margin characteristics influence songbird nest‐site selection in adjacent hedgerows?

Capsule Dunnocks Prunella modularis showed a preference for nesting in hedgerows adjacent to sown rather than grass margins on four farms in southwest England.