Action Synopsis: Bird Conservation About Actions

Provide supplementary food

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Key messages

A replicated, controlled study from Europe found that overall, gardens with supplementary food did not contain more species than those without. However, there was some evidence that gardens with supplementary food in five countries did contain more species than unfed ones, when countries were analysed separately.


For specific interventions see: provide supplementary food

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated controlled study of 440 gardens across 14 countries in Western Europe (excluding the UK) from October 1988 until May 1989 (Thompson et al. 1993) found that 264 gardens frequently provided with supplementary food were visited by an average of 21 species of birds, compared with 22 species for 40 moderately-fed gardens and 21 species for 116 infrequently-fed gardens. Differences were not significant. There was considerable variation across the study area, and feeding frequency appeared to affect the number of species visiting gardens in France and Switzerland, with 17.5 species visiting four infrequently-fed gardens, 13.3 species visiting four moderately-fed gardens and 20.7 species visiting 104 frequently-fed gardens. There was a similar, weaker effect for West Germany, the Netherlands and Belgium. Frequently-fed gardens were provided with food in more than two-thirds of the weeks studied, moderately-fed ones were provided with food for between one and two thirds of the weeks and infrequently-fed ones were provided with food in fewer than one third of the weeks studied.

    Study and other actions tested
Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2020) Bird Conservation. Pages 137-281 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.


Where has this evidence come from?

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Bird Conservation

This Action forms part of the Action Synopsis:

Bird Conservation
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What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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