The term ‘songbirds’ is typically used for the small passerine birds of farmland and woodland such as tits, warblers, thrushes, finches and sparrows. Many of them are resident all year round, like the tits, sparrows and most finches.
Others are migrants, being either present as breeders in the UK during the summer (most warblers), or else winter visitors from Scandinavia or further east (some thrushes).
Many of them share their habitats and predators with small game species. Management for game, ranging from habitat creation and winter food provision to predation control is likely to have consequences for these non-game species.
On farmland over the last 50 years, there have been widespread population declines of many songbird species. Some, such as skylark, tree sparrow, corn bunting and cirl bunting, have experienced more than 50% reductions in abundance, distributional range or both. Many of the declines took place between the mid-1970s and the mid-1980s.
The declines have been associated with a drop in productivity or survival linked to agricultural change. For instance, winter food supplies of seed-eating birds on arable areas are much lower now than previously because of generalised herbicide use, loss of mixed farming and an emphasis on autumn sowing of crops.
Like the grey partridge, many of these seed-eating birds feed their chicks on invertebrates, many of which live on arable weeds or extensive grassland. These invertebrates are getting harder to find, because herbicides remove the weeds, summer insecticides cause direct mortality and not many resources are available in intensively grazed grass. The Environmental Stewardship Scheme and similar schemes brought in by the UK and devolved governments in 2005 offer the opportunity to counteract the economic pressures that have hitherto driven agricultural intensification.
In woodland, numbers of some songbird species have also declined. Unlike on farmland, the nature and timing of the woodland declines vary considerably. Some species show a steady decrease since the 1960s, for others the decline is more recent. Nor is there any obvious commonality in ecology or behaviour, as the declining species include migrants and non-migrants, open nesters and hole nesters, insectivores and seed-eaters. This suggests that different factors may affect different species, with no simple solution.
Over the last 20 years, all these areas have been topics of research for the Game & Wildlife Conservation Trust. The work has sometimes focused on single species (e.g. spotted flycatcher, song thrush and blackbird), and sometimes on bird assemblages such as finches on game cover crops.