Collected Evidence: Collected Evidence: Provide supplementary food for gulls, terns and skuas to increase reproductive success Four studies of three experiments from Europe and Alaska found that providing supplementary food increased fledging success or chick survival in two gull species, although a study from the UK found that this was only true for one island, with abnormally low breeding success. A second island with higher success was not affected by feeding. Two of the experiments fed parent birds and one fed the chicks directly. One study from the Antarctic found no effect of feeding parent skuas on productivity. One study from Alaska found increased chick growth when parents were fed; one study from the Antarctic found no increase in chick growth.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F525https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F525Sat, 08 Sep 2012 13:37:48 +0100Collected Evidence: Collected Evidence: Provide supplementary food for parrots to increase reproductive success Two studies from New Zealand found some evidence that providing supplementary food for kakapos Strigopus habroptilus increased the number of breeding attempts made, whilst a third study found that birds provided with specially-formulated pellets appeared to have larger clutches than those fed on nuts. One study found no evidence that providing food increased the number of nesting attempts.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F536https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F536Sun, 09 Sep 2012 19:43:26 +0100Collected Evidence: Collected Evidence: Provide supplementary food for songbirds to increase reproductive success Two studies from the USA found evidence for higher population densities of magpies and American blackbirds in areas provided with supplementary food, whilst two studies from the UK and Canada found that population densities did not appear to be affected by feeding. Twelve studies from across the world found that breeding productivity was higher for fed birds than controls. The increases were through higher hatching or fledging rates, or higher chick survival or recruitment rates. One study from the USA found that these increases were only found in dry years. Eleven studies from Europe and the USA found that fed birds had no higher, or even lower breeding productivity or chick survival than control birds. Nine studies from Europe and North America found that the eggs of fed birds were larger or heavier, or that the chicks of fed birds were in better physical condition: being larger, heavier, faster growing, more symmetrical or having a better immune response. In one study this was only true in a heavily polluted site. However, eight studies from across the world found no evidence for better condition or increased size in the eggs or chicks of fed birds. Six studies from across the world found that food-supplemented pairs laid larger clutches than unfed birds, whilst 14 studies from Europe and North America found that fed birds did not lay larger clutches, or even laid smaller ones. Fifteen studies from across the world found that birds supplied with supplementary food began nesting or laying earlier than controls, although in two studies this was only true for young females or in one of two habitats. In one study, a high fat, high protein diet had a greater effect on laying date than a high fat, low protein diet.­ One study found that fed birds had shorter incubations than controls whilst another found that fed birds re-nested quicker than controls and had shorter second incubations. Four studies from the USA and Europe found that fed birds did not lay any earlier than controls. Seven studies from across the world found that fed parent birds showed positive behavioural responses to feeding, such as being more likely to re-nest, less likely to be parasitized or  showing better anti-predator responses, spending more time incubating or building larger nests. Three studies from across the world found neutral or negative responses to feeding, including being more likely to be invaded by conspecifics, making no more breeding attempts or showing no preference for fed nest boxes compared to controls.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F537https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F537Sun, 09 Sep 2012 19:58:27 +0100Collected Evidence: Collected Evidence: Provide supplementary food for wildfowl to increase adult survival Two studies from Canada and Northern Ireland found that five species of wildfowl readily consumed supplementary food (grains and seeds). Only the Canadian study assessed the physiological effects of feeding, and found that fed birds were heavier and had larger hearts or flight muscles or had more body fat than controls  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F542https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F542Sun, 16 Sep 2012 08:47:27 +0100Collected Evidence: Collected Evidence: Provide supplementary food for waders to increase adult survivalA study in Northern Ireland found that waders fed on millet seed when provided, but were dominated by mallards Anas platyrhynchos when larger seeds were provided.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F543https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F543Sun, 16 Sep 2012 08:50:12 +0100Collected Evidence: Collected Evidence: Provide supplementary food for vultures to increase adult survival A before-and-after study from Spain found a large increase in griffon vulture Gyps fulvus population in the study area following multiple interventions including supplementary feeding. Two studies from the USA and Israel found that Californian condors Gymnogyps californianus and Egyptian vultures Neophron percnopterus fed on many of the carcasses provided for them. The Egyptian vultures were sometimes dominated by larger species at a feeding station supplied twice a month, but not at one supplied every day.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F545https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F545Sun, 16 Sep 2012 09:10:04 +0100Collected Evidence: Collected Evidence: Provide supplementary food for raptors to increase adult survivalTwo randomised, replicated and controlled studies in the USA found that nesting northern goshawks Accipiter gentilis were significantly heavier in territories supplied with supplementary food, compared with those from unfed territories.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F546https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F546Sun, 16 Sep 2012 09:12:47 +0100Collected Evidence: Collected Evidence: Provide supplementary food for gulls, terns and skuas to increase adult survivalA randomised, replicated and controlled study in the Antarctic found that female south polar skuas Catharacta maccormicki that were fed lost more weight whilst feeding two chicks than unfed birds. There was no difference for birds with single chicks, or male birds.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F548https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F548Sun, 16 Sep 2012 09:21:14 +0100Collected Evidence: Collected Evidence: Provide supplementary food for pigeons to increase adult survival A study of a recently-released pink pigeon Nesoenas mayeri population on Mauritius found that fewer than half the birds used supplementary food, and appeared to survive without it. However, a later study of the population found that almost all birds were recorded using supplementary feeders.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F549https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F549Sun, 16 Sep 2012 09:24:17 +0100Collected Evidence: Collected Evidence: Provide supplementary food for woodpeckers to increase adult survival One replicated, controlled study from the USA found that 12 female downy woodpeckers Picoides pubescens supplied with supplementary food had higher nutritional statuses than unfed birds. However, two analyses of a replicated, controlled study of 378 downy woodpeckers from the USA found that they did not have higher survival rates or nutritional statuses than unfed birds.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F551https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F551Sun, 16 Sep 2012 09:42:41 +0100Collected Evidence: Collected Evidence: Provide supplementary food for songbirds to increase adult survival Seven studies from Europe and the USA found higher densities or larger populations in various songbird species in areas close to supplementary food. Six studies from Europe, Canada and Japan found that population trends or densities in some species were no different between fed and unfed areas. The American study found that populations appeared to follow food, with populations increasing after feeders were erected and decreasing after they were removed. Four studies from Canada, Europe, Japan and the USA found that birds had higher survival when supplied with supplementary food. However, in two studies this was only apparent in females or in one of two species studied. A controlled study in the USA found no evidence that birds were dependent on supplementary food: when food was removed, previously fed birds did not have lower survival than controls. A replicated, controlled study from the USA found that song sparrows Melospiza melodia had lower survival with feeding stations in their territories. Six studies from Europe and the USA found that birds supplied with supplementary food were in better physical condition or had larger fat supplies than unfed birds. However, in one replicated, controlled study this was only the case for females; in another two, only one of three species showed better condition, with one species in one study showing lower condition when fed; a final replicated and controlled study found that differences between treatments were only apparent in the breeding season. Two studies investigated the effect of feeding on behaviours: a randomised, replicated and controlled study in the USA found that male Carolina wrens Thryothorus ludovicianus spent more time singing when supplied with food; a replicated, controlled study in Sweden found no behavioural differences between wood nuthatches Sitta europaea supplied with food, and unfed birds. Thirteen studies from the UK, Canada and the USA investigated use of feeders. Four studies from the USA and the UK found high use of supplementary food by several species, with up to 21% of birds’ daily energy needs coming from feeders. However, another UK study found very low use of food, possibly because the feeder was not positioned close to natural food sources. One UK study found that use of feeders peaked in midwinter, although another found that the exact timing of peak use varied between species. Two replicated trials from the UK finding that the use of feeders increased with distance to houses and decreased with distance to cover, whilst a replicated Candadian study found that American goldfinches Carduelis tristis preferred using bird feeders in high positions. A large-scale replicated study in the UK found that preferences for feeder locations varied between species. Three studies from the UK argue that placing feeders over 1 km apart, and possibly 1.1–1.3 km apart will maximise their use whilst keeping the intervention practical.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F552https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F552Sat, 22 Sep 2012 17:27:20 +0100Collected Evidence: Collected Evidence: Provide supplementary food after release Three studies from found that malleefowl Leipoa ocellata, Andean condors Vultur gryphus and pink pigeons Nesoenas mayeri used supplementary food when it was provided after release. A replicated, controlled study from Australia found that malleefowl had higher survival when supplied with supplementary food. A study in Peru found that supplementary food could be used to increase the foraging range of condors after release, or to guide them back to suitable feeding areas.  Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F639https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F639Sun, 14 Oct 2012 23:54:01 +0100
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.

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