Use of pine snags by birds in different stand types of Scots Pine Pinus sylvestris

Abstract

Capsule Hole-nesting birds tended to breed in the largest pine snags (standing dead trees) predominating in ancient native pinewood and scarce in plantations. Aims To describe and compare the density, volume and sizes of pine snags in different stands of ancient native Scots Pine wood and Scots Pine plantations at Abernethy Forest, and to determine the use made by hole-nesting birds in such stands. Methods The status of snags in different stands was based on samples taken along random transects through the forest. Nests were also searched for along the transects and combined with incidental data. Results Mean snag densities were 15–102/ha, volumes 1.8–28.7 m3/ha, and median diameter at breast height (DBH) 9.2–19.3 cm in different stands of ancient native pinewood. Snag densities were 9–275/ha, volumes 0.4–7.5 m3/ha and DBHs 3.8–9.6 cm in different plantation stands. From this available resource, Great Spotted Woodpeckers Dendrocopos major and Crested Tits Parus cristatus selected the larger snags for excavating nest and roost sites, primarily in ancient native pinewood. Several birds (Swift Apus apus, Wryneck Jynx torquilla, tits and Redstart Phoenicurus phoenicurus) were secondary occupiers of woodpecker excavations. Ducks, Tawny Owl Strix aluco and Kestrel Falco tinnunculus also used holes in large snags for nest sites. It is thought that the main cause of tree death is stem exclusion resulting in relatively few large snags, the sizes that birds prefer. Conclusion Forest and wildlife managers should consider killing some large pine trees (over 40 cm DBH) in plantations where other wildlife interests are not compromised, and thereby provide suitable snags for birds and other wildlife.