Songbird breeding numbers have been monitored since the start of the Allerton Project in 1992. This documented the changes since game management was introduced in 1993, since predator control stopped in 2001, and most recently, since we started our new shoot in 2011.
Two methods have been used – annual transects, and in 1992, 1998, 2001, 2006 and 2010, more intensive mapping of the breeding territories of all songbirds on the farm.
The transect counts show that overall numbers of songbirds increased in response to the game management system, with a sustained decline in the years without predator control. The territory mapping results also show lower numbers after predator control was stopped. This more detailed data enables us to assess changes for individual species, and this reveals considerable differences between them.
For example, of the Biodiversity Action Plan (BAP) species, spotted flycatcher and song thrush increased considerably in the early years of the project and declined rapidly following cessation of predator control. BAP species, linnet and bullfinch show a similar but less dramatic trend, while reed bunting numbers, although small, increased in the later years. Yellowhammer showed a gradual decline throughout the life of the project, whereas whitethroat showed a gradual increase.
Provision of grain in hoppers was stopped in 2006, and this may have contributed to the decline in songbird numbers over this period. For example, species such as blackbird, dunnock and chaffinch make considerable use of pheasant feed hoppers and their numbers declined when winter feeding was reduced. However, species such as spotted flycatcher, song thrush, linnet and bullfinch do not use feed hoppers either because they winter elsewhere or because they do not feed on grain.
Figure 1: Songbird numbers