Action: Reduce nest predation by excluding predators from nests or nesting areas
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A 2011 systematic review found that excluding predators from nests significantly increased hatching success, although individual barriers around nests sometimes had adverse impacts.
See also: Physically protect nests from predators using non-electric fencing; Physically protect nests with individual exclosures/barriers or provide shelters for chicks; Protect bird nests using electric fencing; Use artificial nests that discourage predation; Guard nests to prevent predation; Plant nesting cover to reduce nest predation; Protect nests from ants; Use multiple barriers to protect nests; Use naphthalene to deter mammalian predators; Use snakeskin to deter mammalian nest predators; Play spoken-word radio programs to deter predators; Use 'cat curfews' to reduce predation; Use lion dung to deter domestic cats; Use mirrors to deter nest predators; Use ultrasonic devices to deter cats; Can nest protection increase nest abandonment?; and Can nest protection increase predation of adults and chicks?
As well as direct predation on adults (see previous section), predators can have a devastating impact on bird populations through predating eggs and chicks too young to defend themselves or run away. Species ranging from hedgehogs to pigs to other birds can all affect bird populations in this way and in many cases it is not desirable or practical to remove these species. Therefore the use of barriers and cages to prevent predators from attacking nests is widespread.
These can take the form of barriers or cages around individual nests, fences around groups of nests or suitable nesting areas, or repellents to either disguise the presence of eggs or discourage predators from approaching. We found one systematic review (Smith et al. 2010) which compares these approaches and also investigates potential adverse effects of nest protection.
As in the section on predator removal, several studies perform experiments using artificial nests: either man-made or genuine nests that have been filled with false or real eggs (normally from quail Corturnix spp.) and placed in experimental areas to estimate predation rates.
Supporting evidence from individual studies
A 2011 systematic review (Smith et al. 2011) found that excluding predators using fences (see ‘Physically protect nests from predators using non-electric fencing’) or barriers around individual nests (‘Physically protect nests with individual exclosures/barriers’) significantly increased hatching success. Individual barriers appeared to be slightly (non-significantly) more effective than fences, but some studies found that they increased predation on adults (see ‘Can nest protection increase predation of adult and chick waders?’).