Observations on the Song Thrush Turdus philomelos Brehm at Shadwell Wood SSSI
Fig. 3. Relation between annual rainfall and Song Thrush contacts
Fig. 4. Average annual contacts per visit for Song Thrush and Blackbird
landscape when it boasted dense hedges and frequent song posts. They may now find arable land
less good for foraging. If this is the case one would expect woodland populations to be more
stable, and the results from Shadwell Wood suggest this may be the case despite short term
fluctuations in the numbers of contacts that we cannot explain.
Why arc Song Thrushes very frequent in the summer, yet a month later arc absent from the wood
completely? In 12 years there has not been a single contact between August and October. These
seasonal changes probably reflect the availability of different food sources and the particular needs
of young birds. In the spring (February to April) worms and snails are easy to find both inside and
outside the wood, so thrushes spend only a moderate time in the coppice. Corne summer (May to
July), however, the birds have young and these are best fed on a diet of insects - particularly caterpillars
- that are more abundant within the wood (Simms 1976, 1978). This would explain thrush numbers
being at their highest in the wood at this time. In the autumn thrushes consume large numbers of
berries. Although they are very catholic in their tastes, thrushes do have well recorded preferences for
particular fruits: yew, holly, hawthorn and elder are favourites (Simms op. cit.). Although Shadwell
Wood has a particularly wide range of shrubs, of these favourites it only has haws in any number and
for these it must compete with Blackbirds. It seems likely that the Shadwell Wood thrushes can find
their autumn berries in local gardens and hedges rather than in the wood.
The results also showed that Song Thrush contacts within the wood were higher in dry years. It is
possible that this relates to food availability as well. For much of the year thrushes favour earthworms
Essex Naturalist (New Series) 21 (2004)
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