Urban domestic gardens (II): experimental tests of methods for increasing biodiversity

Published source details Gaston K.J., Smith R.M., Thompson K. & Warren P.H. (2005) Urban domestic gardens (II): experimental tests of methods for increasing biodiversity. Biodiversity and Conservation, 14, 395-413.
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This study is summarised as evidence for the following.

	Action	Category
	Practise ‘wildlife gardening’ Action Link
	Provide artificial nest sites for bumblebees Action Link
	Provide artificial nest sites for solitary bees Action Link

Practise ‘wildlife gardening’

A replicated study in 2000–2002 in 20 urban gardens in Sheffield, UK (Gaston et al. 2005) reported that caterpillars were only occasionally found on potted nettle Urtica dioica plants, and that increasing the number of plants or the age of the plants did not increase the number of caterpillars found. In the three years of the experiment, comma caterpillars Polygonia c-album, (it is unclear whether these were adults or caterpillars) were found on potted nettle plants in one, eight and four of the gardens respectively. In June 2000 one tub of nettles was placed in each of 20 gardens. To encourage new growth half of the stems were cut at the first visit and all at the end of each autumn. To test whether patch size or age of plant affected caterpillar presence, in April 2002 five gardens had their plant replaced with a new plant, five had their original plant, five had their plant replaced with four new plants, and five had their original plant plus three new plants. During the summer and autumn of 2000, 2001 and 2002 nettles were checked for caterpillars and their presence (feeding damage and webs).

(Summarised by: Eleanor Bladon)
Provide artificial nest sites for bumblebees

During a three‐year study in Sheffield, UK, no artificial nest chambers of any design (above ground terracotta plant pots, buried terracotta plant pots with entrance holes at the top (no pipe) and wooden boxes) were occupied by bumblebees Bombus spp. (Gaston et al. 2005). Between 52 and 72 nest boxes were put out each year, in 20 domestic gardens.
Provide artificial nest sites for solitary bees

Three types of nest box were placed in 20 urban gardens in Sheffield, UK, from 2000‐2002. They were occupied by two bee species – Hylaeus communis (10 gardens) and Osmia rufa (two gardens). The most frequently used were those constructed of 20 cm lengths of bamboo stem in plastic pipe, and 4 mm or 6 mm diameter holes drilled into wooden blocks, with uptake in over 50% of gardens over three years (Gaston et al. 2005). Tin cans filled with paper drinking straws (4‐6 mm diameter) and 8‐10 mm holes drilled in wood were less well‐used.