Conservation Evidence: Evidence Data

Collected Evidence: Collected Evidence: Plant wild bird seed or cover mixture All seven studies (based on five replicated experiments and a review) that investigated species richness or diversity were from the UK and found that fields or farms with wild bird cover had higher bird diversity than those without, or that more species were found in wild bird cover than in surrounding habitats. Thirty-two studies out of 33 from the UK and North America that examined abundance and population data, found that bird densities, abundances, nesting densities or use of wild bird cover was higher than in other habitats or management regimes, or that sites with wild bird cover had higher populations than those without. These studies included a systematic review and seven randomised, replicated and controlled studies. Some studies found that this was the case across all species or all species studied, while others found that only a subset showed a preference. Four studies investigated other interventions at the same time. Thirteen of the 33 studies (all replicated and from Europe and the USA), found that bird populations or densities were similar on wild bird cover and other habitats, that some species were not associated with wild bird cover or that birds rarely used wild bird cover. Three studies from the UK and Canada, two replicated, found higher productivities for some or all species monitored on wild bird cover, compared to other habitats. Two replicated and controlled studies from Canada and France found no differences in reproductive success between wild bird cover and other habitats for some or all species studied. Three studies from Europe and the USA investigated survival, with two finding higher survival of grey partridge Perdix perdix released on wild bird cover or of artificial nests in some cover crops. The third found that survival of grey partridge was lower on farms with wild bird cover, possibly due to high predation. Five studies from the UK, three replicated, found that some wild bird cover crops were preferred to others. A randomised, replicated and controlled study and a review from the UK found that the landscape surrounding wild bird cover and their configuration within it affected use by birds. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F187https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F187Sun, 10 Jun 2012 13:10:33 +0100Collected Evidence: Collected Evidence: Provide artificial nesting sites for songbirds Only three studies out of 66 from across the world found low rates of nest box occupancy, although this may be partially the result of publishing biases. Thrushes, crows, swallows and New World warblers were the target species with low rates of use. Thrushes, crows, finches, swallows, wrens, tits, Old World and tyrant flycatchers, New World blackbirds, sparrows, waxbills, starlings and ovenbirds all used nest boxes. One study from the USA found that wrens used nest boxes more frequently than natural cavities. Five studies from across the world found higher population densities or population growth rates in areas with nest boxes, whilst one study from the USA found higher species richness in areas with nest boxes. One study from Chile found that breeding populations (but not non-breeding populations) were higher for two species when next boxes were provided. Twelve studies from across the world found that productivity of birds in nest boxes was higher or similar to those in natural nests. One study found there were more nesting attempts in areas with more nest boxes, although a study from Canada found no differences in behaviour or productivity between areas with high or low densities of nest boxes. Two studies from Europe found lower predation of some species using nest boxes. However, three studies from the USA found low production in nest boxes, either in absolute terms or relative to natural nests. Thirteen studies from across the world founds that use, productivity or usurpation varied with nest box design, whilst seven found no difference in occupation rates or success with different designs. Similarly, fourteen studies found different occupation or success rates depending on the position or orientation of artificial nest sites. Two studies found no difference in success with different positions. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F498https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F498Tue, 04 Sep 2012 13:52:37 +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%2Fwww.conservationevidence.com%2Factions%2F537https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F537Sun, 09 Sep 2012 19:58:27 +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%2Fwww.conservationevidence.com%2Factions%2F552https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F552Sat, 22 Sep 2012 17:27:20 +0100