Action Synopsis: Bird Conservation About Actions

Physically protect nests with individual exclosures/barriers or provide shelters for chicks of songbirds

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

Study locations

Key messages

  • Three studies from across the world found increased fledging success for nests in trees protected by individual barriers. A replicated controlled study from the USA also found higher success for ground-nests protected by individual barriers.
  • Two studies from the UK and Japan found lower predation rates on nests protected by individual barriers.


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 small, replicated and controlled study between 1984 and 1988 in northern South Island and Little Barrier Island, New Zealand (Hamel & McClean 1989) found that moving chicks from natural nests into caged artificial nests appeared to increase fledging success in rifleman Acanthisitta chloris (5% of 44 caged chicks died; 94% natural nests destroyed by predators), whitehead Mohoua albicilla (none of 10 caged chicks died; an estimated 0.68 chicks/successful natural nest died, n = 41 nests) , grey gerygone (warbler) Gerygone igata (13% mortality for 15 caged chicks; 33% for nine uncaged chicks) and shining bronze-cuckoo Chrysococcyx lucidus (Chalcites lucidus) (both caged chicks survived, one uncaged chick died, number of uncaged chicks was not given). In addition, a single chaffinch Fringilla coelebs (an introduced species) was caged and survived. In 1987-88, all chicks from one of six caged grey fantail Rhipidura fuliginosa nests died, whereas no uncaged nests were lost. Cages were made of wire-mesh, stretched to ensure that food could be passed through by the parents but that birds’ heads could not be caught.

    Study and other actions tested
  2. A replicated, controlled study in 1979 on saltmarshes in Florida, USA (Post & Greenlaw 1989) found that protecting seaside sparrow Ammodramus maritimus nests (located near the ground) with cylindrical metal barriers (1.5 m tall with a flexible wire canopy) increased the proportion of nests fledging young from 6% (34 nests) to 48% (42 nests). The main predators excluded were rice rat Oryzomys palustris.

    Study and other actions tested
  3. A before-and-after study on Rarotonga (6,700 ha), Cook Islands (Robertson et al. 1994) found that the nesting success of kakerori (Rarotonga flycatchers) Pomarea dimidiate was higher in 1990-92 when nests were protected with predator guards (30 cm aluminium bands around nesting trees to prevent introduced black rats Rattus rattus from climbing to the nests) than in 1987-89 when guards were not used. However this increase was not significant (nesting success of 36% for 48 nests in 1990-92 vs. 16% for 42 in 1987-89). This study also investigated the use of predator removal through poisoning, discussed in ‘Control mammalian predators on islands’. Using predator guards in predator removal areas did not appear to affect nest survival.

    Study and other actions tested
  4. A replicated before-and-after study from 1999-2000 in a mixed forest in Kyushu, Japan (Yamaguchi et al. 2005) found that the proportion of nest box broods (unprotected nest boxes were predated in 2006 either, but that these were all further away (>300 of varied tits Parus varius and great tits P. major) predated by Japanese martins Martes melampus fell from 12% (92 broods) to 2% (118 broods) and the overall success rate of nests increased from 29% to 44% following the installation of small wooden blocks directly below the entrance hole of the nest boxes in 2000. Overall predation rates fell from 46% to 28% and the number of broods lost to birds fell from three to zero (although this was not significant). The number of broods lost to snakes did not change between years.

    Study and other actions tested
  5. A replicated before-and-after study from 2005-2006 in northwest England (Mainwaring & Hartley 2008) found that the proportion of blue tit Cyanistes caeruleus nests in nestboxes that were predated by great spotted woodpeckers Dendrocopos major fell from 25% in 2005 (57 nests) to 2% in 2006 (48 nests), after the sides of 31 nest boxes were covered in 13 x 13 mm square wire mesh. The authors note that none of the unprotected nests were predated in 2006 either, but that all these boxes were at least 300 m from active woodpecker nests.

    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?

List of journals searched by synopsis

All the journals searched for all synopses

Bird Conservation

This Action forms part of the Action Synopsis:

Bird Conservation
What Works 2021 cover

What Works in Conservation

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.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust