Can nest protection increase predation of adults and chicks?

Overall effectiveness category Evidence not assessed
Number of studies: 5
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Effectiveness

not assessed
Certainty

not assessed
Harms

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Background information and definitions

Nest cages and individual barriers are distinctive and may attract predators if they learn to associate the cages with potential prey. As with the previous section, unless studies specifically mention increased predation, they are discussed in ‘Physically protect nests with individual exclosures/barriers’.

Study locations

Key messages

Three replicated and controlled studies from North America and Sweden found higher levels of predation on adult birds with nest exclosures, one study from Sweden found that predation was no higher.
A replicated and controlled study from Alaska found that long-tailed jaegers Stercorarius longicaudus learned to associate exclosures with birds, targeting adult western sandpipers Calidris mauri and quickly predating chicks when exclosures were removed.

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

A replicated, controlled study from 1993-2002 at five alkali lakes in Alberta and Saskatchewan (Canada), Montana and North Dakota, USA (Murphy et al. 2003) found that adult piping plovers Charadrius melodus were more likely to be predated if their nests were protected by exclosures (5% of 1,355 nests suffering mortality) than if their nests were unprotected (no adults predated at 420 nests). Predation rates were highest (up to 48%) at sites with 4–15% tree cover within 2 km of the nests and zero in areas with few trees (across the study period, 393 nests monitored). At one site, when small (1-1.7 m diameter) exclosures were replaced with large (3-4 m diameter) ones with netting tops, predation rate fell from 34% in 1999 (55 nests) to 11% in 2000 (39 nests) In areas where large cages only were used, predation rates were 0.7% (303 nests). Most (78%) losses were to raptors.
Study and other actions tested
Referenced paper
Murphy R.K., Michaud I.M.G., Prescott D.R.C., Ivan J.S., Anderson B.J. & French-Pombier M.L. (2003) Predation on adult piping plovers at predator exclosure cages. Waterbirds, 26, 150-155.
A replicated before-and-after study on beaches in California, USA (Neuman et al. 2004) found that nest abandonment rates of snowy plovers Charadrius alexandrinus combined with adult mortality increased between 1984-90 and 1991-99 (1% of 728 nests in 1984-90 vs. 4% of 682 in 1991-99) following the protection of 49% of nests with predator exclosures (1.5 m high triangular wire fences) after 1991. In addition, although only 49% of nests were protected, 75% of adult disappearances (assumed to be due to predation) were from protected nests (significantly more than expected by chance). This study is also discussed in ‘Predator control not on islands’, ‘Physically protect nests with individual exclosures/barriers’ and ‘Can nest protection increase nest abandonment?’.
Study and other actions tested
Referenced paper
Neuman K.K., Page G.W., Stenzel L.E., Warriner J.C. & Warriner J.S. (2004) Effect of mammalian predator management on snowy plover breeding success. Waterbirds, 27, 257-263.
A replicated and controlled study in 2001 in the Yukon Delta, Alaska, USA, (Niehaus et al. 2004) found that survival of western sandpiper Calidris mauri nests was higher when they were protected by exclosures (see ‘Physically protect nests with individual exclosures/barriers’). However, after 17 days, long-tailed jaegers (skuas, which predate on sandpiper adults, chicks and eggs) Stercorarius longicaudus began associating exclosures with nests and targeting them (whilst ignoring control nests), causing sandpipers to flush, sometimes colliding with the exclosures. One chick died from cold exposure whilst adults were being harassed by jaegers and exclosures were removed after 19 days. Following exclosure removal, chicks from exclosure nests were less likely to survive than those from control nests, with some chicks being predated minutes after the removal of exclosures.
Study and other actions tested
Referenced paper
Niehaus A.C., Ruthrauff D.R. & McCaffery B.J. (2004) Response of predators to western sandpiper nest exclosures. Waterbirds, 27, 79-82.
A replicated, randomised and controlled trial in 2002 and 2004 at three grazed pasture sites in south-west Sweden (Isaksson et al. 2007) found that there were significantly higher predation rates on adult common redshank Tringa tetanus with protected nests (protected by truncated cone steel cages with 6.5 – 8.5 cm spacing between vertical bars and 4 x 4 cm steel netting on top) than for birds brooding at unprotected nests (nine adults from eight protected nests predated, from a total of 37 nests vs. a single bird from 31 unprotected nests). This study is also discussed in ‘Physically protect nests with individual exclosures/barriers’.
Study and other actions tested
Referenced paper
Isaksson D., Wallander J. & Larsson M. (2007) Managing predation on ground-nesting birds: the effectiveness of nest exclosures. Biological Conservation, 136, 136-142.
A replicated, controlled trial between 1999 and 2004 on pastures in southwest Sweden (Pauliny et al. 2008) found that protecting southern dunlin Calidris alpina schinzii nests with cages (20 cm high truncated cones with 7.5 cm gaps between vertical bars and 4 x 4 cm steel mesh covering the top) did not significantly affect the predation rates on brooding adults (7% of 57 adults at protected nests predated vs. 13% of 16) adults at unprotected nests). This study is also discussed in ‘Physically protect nests with individual exclosures/barriers’.
Study and other actions tested
Referenced paper
Pauliny A., Larsson M. & Bloqvist D. (2008) Nest predation management: effects on reproductive success in endangered shorebirds. Journal of Wildlife Management, 72, 1579-1583.

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

This Action forms part of the Action Synopsis:

Bird Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Protect nests from ants Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
Physically protect nests with individual exclosures/barriers or provide shelters for chicks of waders Action Link	Likely to be beneficial	12	Synopsis Link
Use mirrors to deter nest predators Action Link	No evidence found (no assessment)	0	Synopsis Link