A summary of MSc dissertation by Mary-Beth Charles (summer 2005)
Although many aspects of nightingale biology, habitat preferences and song characteristics are well established, other areas have yet to be studied fully. With regard to diet, few in-depth studies have been undertaken, so it is not known whether prey type and abundance is a factor that limits the number of territories. Although it is not proven, it has been speculated that, since the nightingales are often very vocal at night, they probably do not feed at night. In the UK, feeding usually occurs on bare ground under thickets and in overgrown ditches. This is usually in less dense areas within the same coppice that is also used for nesting. Studies conducted in traditional woodland habitat in Kent showed nightingales fed almost exclusively on the woodland floor where there was also little or no ground vegetation.

The nightingale’s diet includes primarily worms and insects, with spiders, fruit and berries. Faecal samples indicate that beetles, especially weevils, and wood ants were the most frequent items for fledglings and adults, as well as spiders and lepidoptera larvae.

At Paxton Pits nature reserve, six nightingale territories in scrub were selected for invertebrate sampling. This was to investigate what invertebrate prey is available to nightingales within their singing territories. Observations suggested that the nightingales preferred certain areas on the ground (within the cover of vegetation) more than others. Each individual had two or three areas on the ground where they consistently chose to go.

Based on this information, pitfall traps were placed in three areas within each territory as it was assumed that this is where the nightingales were foraging. Three pitfall traps were also laid in open spaces around the perimeter of the territories, where nightingales are thought not to feed normally, to determine whether there was a difference in the species available and the composition of the invertebrate community. Pitfall traps were constructed from simple plastic cups. Holes were dug into the ground, where the cup was placed. Pitfall traps function by simply catching any insects that fall into them as they are moving over the ground. Thirty-six daytime and thirty-six night time samples were collected for four days a week over six weeks. Half of these samples were collected from territory interiors, half from territory exteriors.

Results showed invertebrates to be more abundant within territories and during night hours. Capture rates of the sixteen most abundant families were significantly different across sites, suggesting that nightingales may be generalist eaters. Two families, Carabidae (ground beetles) and Staphylinidae (rove beetles), were consistently common across the six territories; however, further research is required to determine whether they provide a key contribution to the nightingale diet.

Since higher proportions of invertebrates were captured within territories, management suggestions centre on maintaining the scrub habitat within nightingale territories. Scrub management in the form of coppicing should continue at Paxton Pits to promote heavy ground vegetation within nightingale territories and in turn promote a rich and diverse invertebrate community.

The results showed higher invertebrate abundance within singing territories than in adjacent habitat. This may be due to the fact that there were different ground microclimates between interior and exterior locations. Within territories, the climate was cooler since low-lying vegetation shaded most of the ground. The areas adjacent to territories were sparsely vegetated (except for very short grasses and similar flora) and in direct sunlight, providing a much warmer ground climate. If microclimate is not a factor, higher abundance of invertebrates within territories may be due to the cover that the understorey vegetation provides.