Effects of the winter beechmast crop on bird occurrence in British gardens

Capsule Woodland birds were significantly less likely to occur in gardens in years of high beechmast crop.

Aim To test the hypothesis that woodland species that feed on beechmast will have significantly lower occurrence rates at garden feeders in mast years.

Methods Weekly winter occurrence rates at garden feeders between 1970/71 and 1999/2000 for 40 species were analysed in relation to annual beechmast abundance, classified into low, medium and high years. A repeated-measures logistic regression model was used to assess whether beechmast abundance explained further significant variation additional to underlying seasonal and annual trends.

Results Seven species that commonly feed on beechmast showed significantly lower occurrence in gardens in years of highest beechmast abundance: Great Spotted Woodpecker Dendrocopos major, Woodpigeon Columba palumbus, Great Tit Parus major, Coal Tit Periparus ater, Nuthatch Sitta europaea, Jay Garrulus glandarius and Chaffinch Fringilla coelebs. Blackbird Turdus merula and Siskin Carduelis spinus, which showed similar significant patterns, are likely to take beechmast as elements of their diet. Pied Wagtail Motacilla alba was the only insectivorous species to show significant effects, but occurrence was lowest in years of intermediate beechmast abundance. For the latter species, this may have been due to confounding effects of temperature, but there were no such confounding effects of either temperature, or the number of bird feeders provided in gardens, for the other nine species.

Conclusion Use of artificial food sources by birds in gardens is influenced by resources in the surrounding countryside, suggesting that food provided in gardens may play a significant part in the population dynamics of these species, that population monitoring without consideration of the garden habitat may be deficient, and that volunteer-based garden bird recording may provide data that can be used as an indicator of changes in the wider countryside.     

Likeability of Garden Birds: Importance of Species Knowledge & Richness in Connecting People to Nature

Interacting with nature is widely recognised as providing many health and well-being benefits. As people live increasingly urbanised lifestyles, the provision of food for garden birds may create a vital link for connecting people to nature and enabling them to access these benefits. However, it is not clear which factors determine the pleasure that people receive from watching birds at their feeders. These may be dependent on the species that are present, the abundance of individuals and the species richness of birds around the feeders. We quantitatively surveyed urban households from towns in southern England to determine the factors that influence the likeability of 14 common garden bird species, and to assess whether people prefer to see a greater abundance of individuals or increased species richness at their feeders. There was substantial variation in likeability across species, with songbirds being preferred over non-songbirds. Species likeability increased for people who fed birds regularly and who could name the species. We found a strong correlation between the number of species that a person could correctly identify and how connected to nature they felt when they watched garden birds. Species richness was preferred over a greater number of individuals of the same species. Although we do not show causation this study suggests that it is possible to increase the well-being benefits that people gain from watching birds at their feeders. This could be done first through a human to bird approach by encouraging regular interactions between people and their garden birds, such as through learning the species names and providing food. Second, it could be achieved through a bird to human approach by increasing garden songbird diversity because the pleasure that a person receives from watching an individual bird at a feeder is dependent not only on its species but also on the diversity of birds at the feeder.     

Individual variation and seasonality drive bird feeder use during winter in a Mediterranean climate

Purposeful provisioning of food to wild animals is a widespread and growing activity that has the potential to impact populations and communities. Nevertheless, studies assessing use of recreational feeders by free‐living birds during winter are surprisingly rare and largely limited to regions with continental climates characterized by freezing temperatures and snow cover. In contrast, there is little information available regarding bird use of feeders within warmer climates during winter, despite widespread recreational feeding in these areas. In this study, we quantified visitation patterns to bird feeders in a Mediterranean climate to evaluate the relationship between feeder use and several environmental variables known to influence supplemental feeder use in continental climates. We established a network of bird feeders in Corvallis, Oregon, USA, that were filled with black oil sunflower (Helianthus annuus) seeds and equipped with radio frequency identification (RFID) data loggers that recorded >315,000 visits by 70 individual Black‐capped Chickadees (Poecile atricapillus) across a 5‐month period (October 2016–March 2017). We found extensive variation in feeder use, with individuals averaging 1–406 feeder visits/day and using 1–9 of the 21 feeders that were available; individual variability was largely consistent during the course of our study. At the population level, we found that feeder use decreased from the start of our study, and this decline continued through the period when foraging was most limited by daylight, including the winter solstice. In contrast to theoretical predictions and empirical work in continental climates, we found that weather variables did not drive feeder use and that feeder visits peaked at mid‐day and gradually decreased until sunset. Our study indicates that individual‐level differences combined with seasonality to drive feeder use patterns, and we conclude that use of supplemental feeders during winter in Mediterranean climates appears to differ notably from feeder use in continental climates.     

Urban nectarivorous bird communities in Cape Town,South Africa,are structured by ecological generalisation and resource distribution

Biological communities are increasingly faced with novel urban habitats and their response may depend on a combination of biological and habitat traits. The response of pollinator species to urban habitats are of particular importance because all species involved in the pollination mutualism may be affected. Nectarivorous bird communities worldwide show varying tolerances to urban areas, but studies from Africa are lacking. We investigated nectarivorous bird communities in a medium‐sized South African city and asked which biological and garden traits best predict the community assembly of specialist and opportunistic nectarivorous birds. Information was collected on garden traits and the frequency of nine nectarivorous bird species for 193 gardens by means of a questionnaire. Information on biological traits of birds was obtained from published literature. Habitat generalism and tree nesting were identified as the most important biological traits influencing bird occurrence in gardens. A greater diversity of indigenous bird‐pollinated plants and the presence of sugar water feeders increased the numbers of nectar specialist birds and species richness of nectarivorous birds. While bird baths increased the species richness of nectar specialist birds, opportunistic birds’ urban adjustment was further facilitated by large vegetated areas in gardens and limited by the distance to the nearest natural habitat. In conclusion, though some biological traits and dispersal barriers seem to limit urban adjustment, a combination of natural and artificial nectar resource provisioning could facilitate this adjustment.     

Winter feeding of birds increases productivity in the subsequent breeding season

Supplementary food given to birds can have contemporary effects by reducing the risk of starvation, increasing survival and altering movements and reproductive performance. There is, however, a widely held perception that birds benefit from extra food over winter, but that it is better that they 'look after themselves' during breeding. Here we describe a landscape-scale experiment showing for the first time that the effects of increasing food availability only during the winter can be carried over to the subsequent breeding season. Even though food supplementation stopped six weeks prior to breeding, birds living on sites provisioned over winter had advanced laying dates and increased fledging success compared with birds living on unprovisioned sites. Thus, supplemental feeding of wild birds during winter, in a manner mimicking householders provisioning in gardens and backyards, has the potential to alter bird population dynamics by altering future reproductive performance. With levels of bird feeding by the public continuing to increase, the impacts of this additional food supply on wild bird populations may be considerable.     

Breeding bird dynamics in a primaeval temperate forest: long–term trends in Biatowieza National Park (Poland)

Numerical vanation of the breeding bird community, its ecological subunits (guilds) and the 26 most numerous constituent species is analysed over 20 yr period (1975–1994), and related to variation in supply of defoliating caterpillars, tree seed crop, numbers of rodents and winter weather Maximum rates of increase between two years were less than twofold in most species Changes in numbers of individual species/guilds were either independent of each other or in parallel The pattern of numerical vanation was not related to taxonomic affinities, type of nest site, food types, or migratory habits Whole bird community and 13 of 26 species showed long–term increasing trends, only three species declined Numbers remained basically stable during the first decade, increases were concentrated to the second decade Except tropical migrants (no long–term change) other migratory groups increased in numbers None of the measured environmental vanables showed parallel trends, which could account for the recorded trends Long–term trends and year–to–year fluctuations were not correlated The short–term variation in bird numbers was to some extent correlated with (in decreasing order of importance) abundance of defoliating caterpillars, winter seventy, and changes in rodent numbers No correlation with tree seed crop was found Overall, a substantial part of the vanation in breeding bird numbers could not be explained by that set of factors This could be due to birds using wider spectrum of food sources than those measured, varying predator pressure and/or strong influences from outside the forest, swamping local relationships     

Provision of supplementary food for wild birds may increase the risk of local nest predation

In countries such as the UK, USA and Australia, approximately half of all households provide supplementary food for wild birds, making this the public's most common form of active engagement with nature. Year‐round supplementary feeding is currently encouraged by major conservation charities in the UK as it is thought to be of benefit to bird conservation. However, little is understood about how the provision of supplementary food affects the behaviour and ecology of target and non‐target species. Given the scale of supplementary feeding, any negative effects may have important implications for conservation. Potential nest predators are abundant in urban areas and some species frequently visit supplementary feeding stations. We assess whether providing supplementary food affects the likelihood of nest predation in the vicinity of the feeder, by acting as a point attractant for potential nest predators. We provided feeding stations (empty, peanut feeder, peanut feeder with guard to exclude potential nest predators) in an area of suburban parkland in the UK and monitored the predation rate of eggs placed in artificial nests located at distances that replicated the size of typical suburban gardens. Nest predators (Magpies Pica pica, Grey Squirrels Sciurus carolinensis) were frequent visitors to filled feeders, and predation caused by Magpies, European Jays Garrulus glandarius and Grey Squirrels was significantly higher when nests were adjacent to filled feeders. The presence of a feeder guard did not significantly reduce nest predation. As supplementary feeding is becoming increasingly common during the breeding season in suburban habitats, we suggest that providing point attractants to nest predators at this time may have previously unconsidered consequences for the breeding success of urban birds.     

Species interactions and habitat associations of birds inhabiting urban areas of Sydney,Australia

Abstract The absence of small birds from many suburban areas may be due to adverse garden characteristics, interspecific aggression or human behaviour such as supplementary food provisioning that encourages predators. We investigated the relationship between these factors and the presence of seven small bird species in Sydney through a community‐based survey. The survey was conducted by participants over a 7‐day period between 7 am and 10 am in November and early December 2000. Three dominant species, the noisy miner (Manorina melanocephala), pied currawong (Strepera graculina) and common myna (Acridotheres tristis) were each present in over 59% of gardens. Each small bird species was present in less than 40% of gardens. All small birds were negatively associated with noisy miners, but only the silvereye (Zosterops lateralis) was negatively associated with pied currawongs. None of the species of small birds was negatively associated with common mynas. Four species of small birds were associated with at least one habitat variable, notably the proportion of native vegetation. Although more birds were recorded in gardens in which meat was provided, there were significantly fewer small birds in these gardens. There were also more birds recorded in gardens where seed was provided, with red‐browed finches (Neochmia temporalis) positively associated with seed provisioning in most regions of Sydney. The presence of dogs and cats was not related to the total abundance of birds overall or small birds in gardens. While garden characteristics may influence the presence of small birds to some degree, the presence of noisy miners, a species that are thought to aggressively exclude other species from their territories, is likely to be an important influence on these species in suburban areas. Furthermore, supplementary feeding by people is likely to negatively influence some small birds. The presence of carnivorous pets does not seem to influence the presence of small birds at the scale of the individual garden.     

Winter availability of cereal stubbles attracts declining farmland birds and positively influences breeding population trends

Many studies have demonstrated the selection of stubble fields by farmland birds in winter, but none have shown whether provisioning of this key habitat positively influences national population trends for widespread farmland birds. We use two complementary extensive bird surveys undertaken at the same localities in summer and winter and show that the area of stubble in winter attracts increased numbers of several bird species of conservation concern. Moreover, for several farmland specialists, the availability of stubble fields in winter positively influenced the 10 year breeding population trend (1994-2003) whereas hedgerow bird species were less affected. For skylarks and yellowhammers, initially negative trends showed recovery with 10-20 ha of stubble per 1 km square. Thus, agri-environment schemes that promote retention of over-winter stubbles will attract birds locally and are capable of reversing current population declines if stubbles are available in sufficient quantity.     

Associations of garden birds with gradients in garden habitat and local habitat

Habitat associations of 40 bird species were analysed using data from a survey of 12892 garden sites throughout the United Kingdom between 1995 and 2002. Gradients in 20 garden habitat variables and 25 variables describing the surrounding local habitat were derived from Detrended Correspondence Analysis. The main garden axis explained 13.3% of variation in the data and described a gradient from sites containing and bounded by high levels of vegetation cover to open sites bounded by walls and fences. The main local axis explained 29.9% of variation in the data and described a gradient from rural to urban habitats. Higher probability of occurrence was detected in larger sites in 25 species and in smaller sites in four (urban-associated) species. Many species (22 out of 40) were significantly associated with the local gradient: seven species showed the highest probability of occurrence in sites within more urbanised habitats. Other species were most likely to occur in sites within rural or suburban habitats. Only five species showed a significant association with garden habitat gradient, four of these being most likely to occur in sites with highest vegetation cover. These associations were similar when controlling for garden size and for food provision in gardens. The results imply that the likelihood of many species occurring in gardens is dependent on the surrounding local habitat rather than the garden habitat. However, survey participants were likely to have "bird-friendly" gardens which may have reduced the variation in garden habitat across the sample. An assessment of the representativeness of survey sites is needed to further understand habitat associations of garden birds.     

Supplementary feeding of wild birds indirectly affects the local abundance of arthropod prey

Providing supplementary food for wild birds is a globally popular pastime; almost half of the households in many developed countries participate and billions of US dollars are spent annually. Although the direct influence of this additional resource on bird survivorship and fecundity has been studied, there is little understanding of the wider ecological consequences of this massive perturbation to (what are usually) urban ecosystems. We investigated the possible effects of wild bird feeding on the size and survivorship of colonies of a widespread arthropod prey species of many small passerine birds, the pea aphid [Acyrthosiphon pisum (Harris); Hemiptera: Aphididae], in suburban gardens in a large town in southern England. We found significantly fewer aphids and shorter colony survival times in colonies exposed to avian predation compared to protected controls in gardens with a bird feeder but no such differences between exposed and protected colonies in gardens that did not feed birds. Our work therefore suggests that supplementary feeding of wild birds in gardens may indirectly influence population sizes and survivorship of their arthropod prey and highlights the need for further research into the potential effects on other species.     

Testing agri‐environment delivery for farmland birds at the farm scale: the Hillesden experiment

The Hillesden experiment, established in 2005/2006 to test the delivery of biodiversity benefits under Environmental Stewardship, covers c. 1000 ha of arable farmland in central lowland England. It is a randomized block experiment with five replicates of three treatments: (1) CC: cross compliance, the control; (2) ELS: 1% of land removed from production for wildlife habitat provision; and (3) ELS‐X: 5% of land used for wildlife habitat, each treatment being applied to contiguous areas of 70–80 ha. Bird usage of winter food patches, comprising three different seed mixes, was monitored through the winter and was also related to seed yield. Winter and breeding season bird/territory abundance was recorded before and after the provision of the winter food patches. Bird use of the patches differed between seed mixes. There was large variation between individual patches in both seed yield and bird numbers and between individual bird species in their use of different seed mixes, suggesting that the availability of a range of patch types would be beneficial. Use of all patch types declined sharply in late January to February, indicating depletion and/or inability of birds to access shed seed. Winter bird abundance at a farm scale for all species combined, granivorous species and nine individual species increased for all monitored species when seed patches were available. At a treatment level, the increases tended to be greater in ELS‐X, where most of the patches were located. In the breeding season at a farm scale, the numbers of territories for all species combined and granivorous species increased significantly when seed patches had been available in the previous winter. There was little evidence of a treatment‐scale response. The provision of winter food appeared to increase winter bird abundance and to follow on into an overall increase in the breeding population, but if the latter effect is to be reflected elsewhere, this requires that sufficient breeding habitat is available to accommodate an increase.     

Assessing the potential for Grey Squirrels Sciurus carolinensis to compete with birds at supplementary feeding stations

Supplementary feeding of birds, particularly in urban areas, is often associated with increased population size and fecundity. In the UK, the non‐native Grey Squirrel Sciurus carolinensis is common in rural and urban habitats. It exploits supplementary feeders and may induce interference competition by excluding birds, but empirical evidence of this is unavailable. Using controlled model presentation experiments, we demonstrate that Grey Squirrels could reduce bird use of supplementary feeders and induce interference competition. Total bird resource use was reduced by 98% and most species exhibited similar sensitivities. The likelihood and magnitude of interference competition will depend on how rapidly displaced birds find alternative food sources; it will be greatest where there are high Grey Squirrel densities and few supplementary feeders. Other studies suggest that supplementary feeding increases Grey Squirrel numbers, and the species is also predicted to expand its non‐native range across most of Europe. Our data indicate that Grey Squirrels may eventually alter the net effect of supplementary feeding on bird populations across the European continent; increased use of squirrel‐proof feeders may help to minimize such effects.     

Urban bird trends in a rapidly growing tropical city

Long-term studies of urban birds are relatively scarce, especially in Africa. We analysed trends in species richness and bird species occurrence over a 32-year period in Kampala, Uganda, in order to assess changes in the bird community in a period that has shown rapid expansion of the city's human population. Given that species may respond to urbanisation according to their diet, we also analysed bird community trends of species groups defined according to predominant diet. There was an overall decline in species richness that was largely driven by declines in insectivores and granivores. General declines were evident also when the trends in the most common individual species in these two groups were considered. The occurrence of the commonest predator and scavenger species tended to increase over the period considered. Insectivorous species are likely to be especially affected by increasing urbanisation due to air pollution. Predators and scavengers are likely to have benefitted from the inability of municipal waste management to keep pace with growth in the human population, hence providing more potential food resources. Both insectivores and predators/scavengers are therefore good candidates for the development of urban indicators.     

Winter bird communities in the northern Negev: species dispersal patterns, habitat use and implications for habitat conservation

Bird habitat conservation may require different management strategies for different seasonal bird assemblages. We studied habitat use by winter birds in forest and scrubland habitat patches in the northern Negev, Israel. Our goal was to assess whether differences in responses to landscape and habitat structure between breeding and non-breeding seasons require changes in future conservation plans that have been suggested for the Negev breeding bird community. We evaluated habitat and area effects on bird abundance and distribution and tested whether species habitat use during winter involves niche shifts. Compared with breeding birds, a larger proportion of winter bird species occupied both scrubland and forest. As in summer, forest bird species responded to habitat structure, whereas scrubland species were associated with both habitat structure and area. Resident birds disperse into habitats in which they were not present during summer. Consequently, for several species, the correlation between bird densities and environmental factors showed a better fit at the landscape rather than at the habitat scale. In addition, rather than niche shift, birds actually extended their niche breadth. Nest site selection may constrain bird distribution into a realized niche, smaller than their fundamental niche. Despite the scale differences in habitat use, the similar species diversity patterns between seasons suggest that both winter and summer birds would benefit from conservation of scrub patches larger than 50 ha, and enrichment of foliage layers within the planted forests.     

Garden bird feeding predicts the structure of urban avian assemblages

Households across the developed world cumulatively spend many millions of dollars annually on feeding garden birds. While beneficial effects on avian assemblages are frequently claimed, the relationships between levels of garden bird feeding and local avian populations are unknown. Using data from a large UK city, we show that both avian species richness and abundance vary across different socioeconomic neighbourhood types. We examined whether patterns in bird feeding could explain this variation. The density of bird feeding stations across the urban environment was strongly positively related to avian abundance, after controlling for differences in habitat availability. This effect was almost exclusively driven by the abundance of those species known to utilize garden feeding stations frequently. In contrast, the density of feeding stations had no effect on avian species richness. We also examined variation in the proportion of households in different communities that provide food for birds, a factor that is not correlated with feeder density. The prevalence of bird feeding across different neighbourhoods declined as socioeconomic deprivation increased, and increased with avian species richness and abundance. Our results suggest that the provision of supplementary food for birds by multiple landowners across a city can impact the status of urban bird populations. The potential for harnessing these actions for conservation needs to be explored.     

Eye size and the time of arrival of birds at garden feeding stations in winter

A nationwide volunteer survey was conducted to investigate the time at which common species of birds arrived at garden feeders in the morning during winter, and over 5,800 participants submitted observations. We examined the relationship between species’ eye size and their time of arrival at feeders, in order to investigate whether the time at which foraging was initiated was constrained by visual capability. There was a negative correlation between eye size and time of arrival at garden feeders across species, and this relationship remained significant when body mass was taken into account. This suggests that the time at which garden birds begin to forage on winter mornings may be limited by their visual capability at low light intensities.     

Changes in timing, duration, and symmetry of molt of Hawaiian forest birds

Food limitation greatly affects bird breeding performance, but the effect of nutritive stress on molt has barely been investigated outside of laboratory settings. Here we show changes in molting patterns for an entire native Hawaiian bird community at 1650-1900 m elevation on the Island of Hawaii between 1989-1999 and 2000-2006, associated with severe food limitation throughout the year beginning in 2000. Young birds and adults of all species took longer to complete their molt, including months never or rarely used during the 1989-1999 decade. These included the cold winter months and even the early months of the following breeding season. In addition, more adults of most species initiated their molt one to two months earlier, during the breeding season. Suspended molt, indicated by birds temporarily not molting primary flight feathers during the months of peak primary molt, increased in prevalence. Food limitation reached the point where individuals of all species had asymmetric molt, with different primary flight feathers molted on each wing. These multiple changes in molt, unprecedented in birds, had survival consequences. Adult birds captured during January to March, 2000-2004, had lower survival in four of five species with little effect of extended molt. Extended molt may be adaptive for a nutrient stressed bird to survive warm temperatures but not cool winter temperatures that may obliterate the energy savings. The changing molt of Hawaiian birds has many implications for conservation and for understanding life history aspects of molt of tropical birds.     

Individual differences in the use of social information in foraging by captive great tits

We investigated individual differences in copying behaviour of captive great tits, Parus major, by analysing their response to a tutor indicating a new feeding site. We used two groups, each of seven male birds, labelled 'fast' and 'slow' explorers based on previous studies in which consistent individual differences in the speed of exploring were found. The birds were trained to search for food hidden in a number of differently coloured and shaped feeders, and later to search in only one type of feeder. During the tests, food was absent and the birds were observed in two different situations: alone or in the presence of a tutor, a bird that had been trained to feed in a different kind of feeder. When alone, slow birds readily extended their search to other feeders while fast birds did not change their routine of visiting the previously rewarded ones. In the presence of the tutor, the opposite occurred: slow birds did not change their behaviour while fast birds significantly increased their visits to the feeders indicated by the tutor. Fast and slow individuals thus differ in their foraging and copying behaviour, consistent with the producer-scrounger model. Copyright 2000 The Association for the Study of Animal Behaviour.     

北京城市鸟类对食源植物利用规律

园林植物为城市生活的鸟类提供重要食物资源,园林中的植物配置会影响城市中鸟类的种类、数量和群落结构.研究城市鸟类与食源植物的关系,可明确鸟类对食源植物的取食关系,为提高城市鸟类多样性提供技术支撑.2017至2019年,在北京市范围内,以直接观察法和野外照片识别法记录鸟类取食的食源植物种类和数量.共选取6个研究地点,每个研...