Song Thrush
From Wild Warwickshire
Contents |
Status Information
Status: A - Species recorded naturally since 1950 (Brown and Grice, 2005).
Regional Status: Much declined, though still abundant, resident, passage migrant and winter visitor (Harrison and Harrison, 2005).
Index of Abundance: 9 – Extremely Abundant Population Estimates: 990,000 territories (Brown and Grice, 2005). 1,030,000 territories best estimate 2000, (Baker et al, 2006). Song Thrush populations have shown a dramatic fall of 72% between 1967 and 1999 (Brown and Grice, 2005).
National Distribution: Present in 100% of 10km squares in England in1988-91 (Brown and Grice, 2005)
SPEC Category: 4 – Populations are concentrated in the EU and have favourable conservation status.
EU Threat Category: None
UK Conservation List: Red
Legal Protection: Wildlife and Countryside Act Schedule II/2 and EU Birds Directive Annex 3 (I)
Species Information
Social Organisation: Territorial (Wernham et al, 2002).
Age at First Breeding: 1 (Wernham et al, 2002).
Breeding Season: Start of May and runs for 19 weeks (Wernham et al, 2002) Song Thrush lay from week 11 with clutch sizes of 4.
Breeding Dispersal Distance: 4 km (Wernham et al, 2002).
Natal Dispersal Distance: 7km (Wernham et al, 2002).
Survival Rate: 0.563 (Wernham et al, 2002).
Habitat Information
General Habitat
Song Thrushes inhabit a variety of habitats from woodland, fields and towns. Studies in 1989 showed densities in woodlands to be 25 territories per km2 and in farmland 5 territories per km2 (Brown and Grice, 2005). Work by Mason (2005) has revealed that extinction rates of Song Thrush in woods are 20-30% in woods less then 10 ha in size illustrating a requirement for large stable woodlands (Brown and Grice, 2005). Success in agricultural landscapes is variable, they have been shown not to select fallow in set aside despite the expectation that the increased invertebrates provided by them would be of benefit (Buckingham et al, 1999).
Breeding Habitat
During the breeding season Song Thrushes requires patches of mature scrub for nesting and short grassland for foraging (Kirby et al, 2000). Non-Breeding Habitat: Outside of the breeding season Song Thrushes are dependant on fruit bearing plants and areas with greater than 25% of holly, hawthorn or blackthorn (Kirby et al, 2000).
Feeding and Behaviour
Food Requirements: Song Thrushes have a varied diet of fruit and insects. They are particularly dependant on fruit crops in autumn and winter. Invertebrates such as Earthworms and snails are taken throughout the year (Snow and Perrins, 1998; Kirby et al, 2002).
Migratory Habits: Most British populations of Song Thrush are sedentary. Those that are migratory tend to be more northerly. Incoming populations are from France and Spain (Wernham et al, 2002).
Causes of Decline
The change in Song Thrush numbers is filled with contradictions, between 1966 and 1981 there was no change in breeding success and the success of each nesting actually increased despite a falling population (Brown and Grice, 2005). First year survival has declined since 1975 (Brown and Grice, 2005) suggesting that whilst breeding is successful many individuals are not reaching maturity. Evidence from the Farmland CBC has shown that percentage abundance has fallen dramatically but presence/absence in 10km squares didn’t alter. This suggests that there is no contraction of range (Brown and Grice, 2005). One key factor is likely climate, Song Thrushes are notoriously vulnerable to cold winters (Brown and Grice, 2005) and in the midlands the severe winter of 1962/63 drastically reduced populations (Lords and Munns, 1968). The fact that recovery from this decline only took 2 years illustrates the species potential for resilience. It is likely that climatic changes affecting the fruiting of key food plants and the availability of invertebrates are key to their decline. The reduction and isolation of woodlands and changing agricultural practices in the past 50 years have all contribute to a decline, reducing nesting sites and foraging territories.
Beneficial Management
- Protection of Woodlands
- Provision of fruit bushes
- Garden Feeding
- Increase in Hedgerows and Beetle banks to increase invertebrate habitat.
County Distribution and Baseline
Song Thrushes are under recorded in WMBC Annual Bird reports, many consider them too common to warrant recording and submitting to the County Recorder, and therefore the data is both limited and often skewed. As a result the data from the WMBC can only really be used to identify a number of key sites. One such site is Wormleighton, here large flocks of Thrushes have been sighted every winter since 1996 with numbers consistently in the 200-400 range (Fig. 31). The second site is DM Kineton the army base in south Warwickshire. This site has had regular counts made in the breeding season and has there are consistent records from 1993 (Fig 31).
Figure 1. Table showing Key Site Information
| Bidford on Avon | Birchmoor | Dosthill/Kingsbury | DM Kineton | Fenny Compton | Wormleighton | |
| 1994 | 10 | - | - | - | - | - |
| 1995 | 9 | - | - | 69 | 400 | - |
| 1996 | 9 | - | - | 34 | 250 | - |
| 1997 | 5 | - | - | 40 | 150 | 210 |
| 1998 | 10 | - | 13 | 30 | 120 | 165 |
| 1999 | 7 | 7 | 16 | 39 | 150 | - |
| 2000 | 11 | 11 | 10 | 63 | 120 | 170 |
| 2001 | - | 11 | 8 | - | 140 | 300 |
| 2002 | 9 | 11 | 8 | 73 | 150 | 300 |
| 2003 | - | - | - | 74 | 185 | 100 |
(Those in bold are winter maxima counts the rest are breeding pairs.)
Breeding Bird Survey Data derived from the BBS (Figure 2) shows a rough increase in Song Thrush numbers with numbers slightly better in the West Midlands as compared to the national picture.
Figure 2. Regional and National BBS Analysis of Song Thrush Populations
Monitoring
Given that Breeding Bird Data is so un-representative for the county monitoring of Song Thrush is particularly difficult. There are no set procedures for monitoring specifically this species. It makes the most sense to run a focused survey in the breeding season to assess the number of pairs in the county. Records from DM Kineton give a good baseline for comparisons and give a general feel for trends in Song Thrush productivity and survival it doesn’t however help assess the strength of the species in the rest of the county.
Song Thrush’s breed in woodland and parkland and it would be worth undertaking a targeted survey of breeding in a selection of core woodlands in the county. Such a survey should use a territory mapping approach.
References
Categories: LBAP | Birds | Species
