Individual study: Comparison of use of shallow or deep nest boxes by tits Parus spp. at Culbin Forest, Nairnshire, Scotland
Summers R.W. & Taylor W.G. (1996) Use by tits of nest boxes of different designs in pinewoods. Bird Study, 43, 138-141
In the British Isles, the crested tit Parus cristatus is restricted to Scotland where it is an uncommon species confined mostly to Scots pine Pinus sylvestris forests. Three common and widespread tits, coal tit P.ater, blue tit P.caeruleus and great tit P.major, regularly use nest boxes but crested tits do not. This may perhaps be because the nest box design is unsuitable. Studies were therefore undertaken to design a suitable nest box for crested tits which generally use rotting tree stumps in which to excavate a nest cavity. In one experiment, (for a summary see: www.conservationevidence.com/EditEntry.asp?ID=152) given that crested tits excavate their own nest cavity, boxes were part-filled with sawdust and wood-shavings to see if this enhanced nest box uptake. In a second experiment (described here), uptake of two different nest box types (shallow and deep) were compared in a pine forest in eastern Scotland.
Study site: The experiment was conducted at Culbin Forest Site of Special Scientific Interest (a former Scots pine Pinus sylvestris and Corsican pine P.nigra plantation) on the Moray coast, eastern Scotland. Since the 1970s there have been about 300 nest boxes sited within the wood.
Net box design and placement: In January 1991, nest boxes of two different designs were installed in pairs (at 1.5 m height, on similarly sized trees a few metres apart, at a similar aspect) in the forest. The two designs were:
i) 'Shallow' boxes - 11.5 cm long x 10.5 cm wide x 15 cm deep, entrance hole diameter 33 mm, its centre 5 cm from the top of the face of the box). These were of the same dimensions as the 300 or so boxes already present in the Forest;
ii) 'Deep' boxes - 12 x 8 x 25 cm deep, entrance hole diameter 33 mm, its centre 5 cm from the top of the face of the box.
All boxes were new at the start of the experiment. During the breeding season boxes were regularly checked for nest lining and eggs.
A total of 10 deep nest boxes of the 32 available were occupied and eggs laid; great tit (3), blue tit (5) and coal tit (2). Only one of the shallow boxes of the 64 available were occupied, this by a pair of crested tits.
Conclusions: These results, taken on there own (see also www.conservationevidence.com/EditEntry.asp?ID=154), are rather inconclusive due to the small sample size, rather low uptake of boxes and short duration (conducted over one breeding season) of the experiment. The results however, concur with other studies that show great tits have a preference for 'deep' nest boxes, and suggests that blue and coal tits also prefer deeper boxes. The preference for deeper boxes may be to avoid potential predators such at great spotted woodpecker Dendrocopus major and red squirrel Scirus vulgaris, which may reach in and take young.
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