Observations on the Song Thrush Turdus philomelos Brehm at Shadwell Wood SSSI
RAY TABOR
The Essex Wildlife Trust, Abbott's Hall Farm, Great Wigborough, Colchester, Essex C05 7RZ
Abstract
Song Thrush numbers have shown a steep decline over the past 25 years. This loss has occurred
mainly on farmland and in gardens. In woodlands this effect is less severe and this paper charts
annual and seasonal changes in the number of birds contacted in a small Essex woodland over a 12
year period. The study reveals no significant change in the number of contacts over the test period.
But interesting data on seasonal variations in contacts, habitat preferences, and the effect of climatic
changes on the bird's use of the woodland are described and discussed. Some possible lessons for
the conservation of the species are suggested from the observations made.
Background
Although common and widespread, Song Thrush populations have declined nationally by around
70% between 1970 and 1995 (Balmer & Vickery 2004). These losses have been particularly severe
in arable farmland. As a result, the Song Thrush is now on the Essex and U.K. Biodiversity Action
Plans. This report describes the status of the species in a 14 acre ancient woodland nature reserve
of the Essex Wildlife Trust.
Survey Methodology
For 12 years, from 1989 to 2000 inclusive, the bird population of Shadwell Wood was monitored by a
series of visits made five or six times a year, spread throughout the 12 months. At every visit the
surveyor walked a standard route around the wood, which lasted approximately 1 Vi to 2 hours. Every
contact with a bird, whether by sight or sound, was recorded together with the position in the wood
where contact was made. The timing of the visits was also reasonably constant, usually late morning.
No attempt was made to confirm whether or not a species was nesting, and of course contact may have
been made with the same individual more than once. Whilst this differs from breeding bird census
work, the relatively easy methodology docs allow for year on year comparisons of "contacts" made.
Summary of findings for the Song Thrush
Population Changes - Although there were variations in the number of contacts from year to year,
there was no significant change in the average number of sightings per visit. Comparing the period
1989 to 1994 with the period 1995 to 2000, the mean number of sightings has increased slightly
from 0.5 to 0.65 although there is no significant difference (using Student's 't' test) between the
two sets of figures. Fig. 1 shows the mean contact figures for each of the 12 years.
Seasonal variations - There were significant and consistent differences in the number of contacts
at different times of year. The greatest frequency of contacts always occurred in the summer (86%
of visits giving a positive result), followed by the winter (45%). Remarkably, in the 12 years of
surveying there has not been a single sighting during the autumn months of August, September and
October (Fig. 2).
Habitat - The Song Thrushes of Shadwell Wood show a strong preference for the shrubby, coppiced
areas of the wood. Just over 80% of contacts were in these areas. This preference was not shared to
Essex Naturalist (New Series) 21 (2004)
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