Wild Bird Feeding Research Articles

Seed and feeder use by birds in the United States and Canada

ABSTRACTMore people feed birds and other wildlife than hunt and fish combined. Despite its popularity, many bird‐feeding traditions lack scientific data. We examined seed and feeder use by wild birds in the United States and Canada, and how seed use may change by season and geographic region. Between 2005 and 2008, 173 individuals from 38 states and 3 provinces in Canada made 20,077, 45‐minute observations at bird feeders, recording 106 species and 1,282,424 bird visits. Of the 10 seed types most commonly used in bird seed blends, 3 are most attractive to birds: black‐oil sunflower, medium sunflower chips, and white proso millet. Other seeds such as red milo are less attractive. Chickadees (Poecile spp.), nuthatches (Sitta spp.), and larger finches (Carpodacus spp.) were most abundant at black‐oil sunflower, smaller finches (Carduelis spp.) were most abundant at Nyjer® (Wild Bird Feeding Institute, Chicago, IL) and sunflower chips, and sparrows (Spizella spp.) were most abundant at white proso millet. Bird‐feeding traditions have been widely reported in books, magazines, newspaper articles, and websites. These traditions are often conflicting and have not been verified empirically. Studies such as this can be used to develop scientifically based recommendations that can lead to a better bird‐feeding experience and that attract fewer species with known negative ecological consequences. © 2013 The Wildlife Society.

A comparison of bird-feeding practices in the United States and Canada

Millions of Americans and Canadians participate in the feeding of wild birds. We surveyed hobbyists about their bird-feeding experience, and examined demographic and regional differences in responses, to determine the types of bird-feeding practices taking place and to identify themes important for wildlife managers to communicate with people who feed birds. Between autumn 2005 and winter 2008–2009, we recruited a non-random sample from the interested public though both print and electronic media. We had 1,291 individuals from 48 states (USA) and 7 Canadian provinces who completed our mail and website survey. Survey respondents were primarily female (67%) and ≥45 years old (77%). Most respondents offered alternative foods in addition to traditional bird seed (≥82%) and provided other resources besides food to attract birds (≥75%). Our respondents fed birds because it brought nature (84%) and accompanying sound (81%) to the area, as a hobby (79%), and to help the birds (79%). Respondents felt attracting more bird species (69%), a greater number of birds (41%), and no pests (35%) would make their bird-feeding experience more satisfying. Given the interested public's desire to increase bird diversity at their feeders and to help birds, managers have the opportunity to develop messages promoting habitat enhancement in addition to feeding, and provide suggestions for reducing the risk of disease transmission and pest species at feeders. © 2013 The Wildlife Society.

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.

Wild bird feeding delays start of dawn singing in the great tit

Supplementary feeding of wild birds during winter is one of the most popular wildlife management activities, and is likely to have profound influence on the behavioural ecology of a species. At garden bird feeders, birds are now often fed well into the breeding season. Providing food within an established songbird territory, however, is likely to influence the territorial behaviour of the resident male. We used song performance during the dawn chorus in early spring to study behavioural changes in food-supplemented great tits, Parus major. After 2 weeks of continuous food supply within their territory, supplemented males started dawn singing later than control males, and thus postponed their regular dawn chorus before sunrise. This effect was maintained 2 weeks after food supplementation had ended. However, we did not find an effect of long-term feeding on song output. Our results were largely unexpected because formal models and field studies on short-term food supplementation suggested an earlier start of dawn singing or a higher dawn song output. Because we did not observe great tits visiting the feeders before sunrise or food supplementation increasing the numbers of conspecific intruders, the reasons for the delay in the start of dawn singing remain unclear; possible explanations include the presence of predators at feeding stations and the quality of the supplementary food itself. Delaying dawn singing could potentially affect the reproductive success of supplemented males, for example if females base extrapair mating decisions on dawn song performance of their mates.

Feeding birds in our towns and cities: a global research opportunity

Wild bird feeding is one of the most common forms of human‐wildlife interactions in the Western world. Originally a practice providing nutritional assistance to over‐wintering birds, especially in more northern latitudes, birds throughout the cities of the world are now provided with considerable amounts and a variety of foods year‐round. Despite the global nature of the practice, remarkably little is known about the outcomes and implications of what may be seen as a supplementary feeding experiment on a massive scale. Although many claims are made about the benefits of feeding, there are growing concerns about the spread of disease, poor nutrition, risk of dependency and many other important issues. Constructive debate among increasingly vigorous proponents and opponents is currently constrained by a lack of reliable information. Here we argue that bird feeding provides an important, if challenging, opportunity for fundamental research in urban ecology.

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.

The Educational Benefits of a Ten-Week Home-Based Wild Bird Feeding Program for Children

ABSTRACTThis study evaluated a ten-week educational home-based program for feeding wild birds, intended to increase elementary school age children's knowledge about birds, especially those wild birds commonly encountered at outdoor home feeders. We measured changes from pre- to post-program in 65 seven- to 12-year old children's knowledge about wild birds, as well as in environmental attitudes. The goal was not only to increase bird knowledge in the target child but also to involve other family members in home-based nature education activities. After the program, seven- to nine-year old boys and girls showed significant gains in bird knowledge, but older children (10–12 years) did not significantly improve. Children's increased knowledge was positively associated with parental education. There was no systematic change in environmental attitudes. Parents identified family involvement as a particularly beneficial aspect of the program, and 90% of contacted families were still feeding birds one year after program termination.

The influence of density on frequency-dependent food selection: a comparison of four experiments with wild birds.

We compare the results of four experiments, conducted at different times and with different protocols, that explored the relationship between frequency-dependent selection and prey density in wild birds feeding on artificial populations of coloured baits. One (experiment 4) used pastry baits that differed only in the presence or absence of a red stripe, and this experiment provided no evidence for any kind of selective behaviour. The other three experiments used green and brown baits, and they all provided evidence for a trend towards increasing anti-apostatic selection with high densities (>100 baits m-2). However, one of these (experiment 3) provided no evidence for frequency-dependent selection at low densities (0.5-20 baits m-2), while the other two experiments concurred in suggesting a trend towards increasing apostatic selection with low densities (down to 2 baits m-2). Together, these experiments both support and qualify the published findings of experiment 1 that frequency- dependent selection by wild birds on bait populations is modified by density. Experiment 4 indicates that frequency-dependent selection may break down entirely if bait types are too similar, while experiment 3 indicates that some details of this trend with density will depend either on the protocol used or on exogenous changes in the birds' feeding behaviour.

The influence of density on frequency–dependent selection by wild birds feeding on artificial prey

Previous work has demonstrated frequency–dependent selection by wild garden birds when feeding on green and brown pastry ‘baits’. When the density of baits is low, the common colour is eaten disproportionately more than the rare colour (apostatic selection), and when the density is very high, the rare colour is eaten disproportionately more than the common (anti–apostatic selection). We explored the relationship between frequency–dependent predation and density in an experiment at 16 separate sites, using four levels of density and two frequencies of green and brown. Analysis of estimates of log–relative risk ratios showed little evidence for frequency–independent selection, but frequency–dependent selection changed gradually from apostatic at low density to anti–apostatic at high density. The validity of these conclusions in terms of individual bird behaviour was confirmed by Monte–Carlo simulations. We thus conclude that selection by wild birds feeding on green and brown artificial prey is frequency dependent, and that the strength and direction of this selection changes with prey density in a gradual and predictable manner.

Does prey dispersion affect frequency-dependent predation by wild birds?

Despite the fact that the vast majority of natural prey items are dispersed in a non-random manner, few studies of frequency-dependent selective predation have explicitly examined the effect of prey dispersion on selectivity. We examined the effect of prey dispersion on the direction and strength of frequency-dependent selection by wild birds feeding on artificial prey (green or brown pastry baits). In a series of four experimental manipulations, we tested for the occurrence of frequency dependence with two different dispersion patterns (random or clumped). Manipulations were carried out at one of two absolute densities (25 prey m-2 or 100 prey m-2), and were repeated at different sites in Southampton, England and Aljarafe, Spain. Our results suggest that prey dispersion has no effect on either frequency-dependent or -independent preferences. One possible explanation for this is that the birds had virtually complete information about prey frequencies at the relatively high densities used and based their preferences on their overall perception of availability. However, we cannot rule out the possibility that dispersion may influence selectivity when prey are cryptic or available at lower absolute densities. Although there was no effect of dispersion, frequency-dependent selection was, overall, significantly anti-apostatic (i.e. rare baits were more preferred than common baits). This anti-apostatic effect was stronger in Southampton than Aljarafe and stronger at 100 prey m-2 than 25 prey m-2. The differences in the strength of selection between the two locations was interpreted in terms of (i) whether the avian predators foraged in flocks or not, and (ii) the number of different species present (and, consequently, the variation in preference among individual birds).

The restoration of the Mauritius Kestrel Falco punctatus population

By 1974, the Mauritius Kestrel Falco punctatus had declined to only four known wild birds, including one breeding pair, as a result of habitat loss and pesticide contamination. A conservation project begun in 1973 has used many management techniques including captive breeding, supplemental feeding of wild birds, provision of nestboxes, multiple clutching, egg pulling, artificial incubation, hand rearing and release of captive‐bred and captive‐reared birds by hacking, fostering and predator control. A total of 331 kestrels were released in the 10 years up to the end of the 1993–1994 breeding season; one‐third of these were captive bred, the rest were derived from eggs harvested from the wild. About 257 (78%) released birds survived to independence and 61% of independent juveniles survived their first winter. Although at least 71% of ringed birds attempted to breed in their first year, only 38% of the nests of first‐year females successfully fledged young, averaging 1.7 per successful nest. Older females fledged young from 64% of nests, fledging an average of 2.0 per successful nest. The breeding success of hacked birds was similar to that of parent‐raised kestrels, though the clutches of hacked birds tended to be larger. Annual replacement of birds holding territories averaged 17% for both sexes. By the 1993–1994 season, an estimated 56–68 pairs had established territories in the wild with a post‐breeding population, including floating birds and independent young, of 222–286. Most of the kestrels were in three sub‐populations, two of which were derived entirely from released birds. Mauritius Kestrels are relatively sedentary; 89% of ringed birds found nesting were less than 5 km from their release or Hedging site. Since the pesticides responsible for their decline are no longer used, the number of Mauritius Kestrels should continue to rise through natural recruitment. The distribution of suitable habitat suggests that an eventual population of 500–600 kestrels on Mauritius is possible. Due to its outstanding success, the release programme for the Mauritius Kestrel ended after the 1993–1994 breeding season, though the population will continue to be monitored carefully for at least the next 5 years.

Wild Birds Prefer the Familiar Colour Pattern When Feeding on Similar Artificial Morphs

Apostatic (frequency-dependent) selection by visually hunting predators could be responsible for maintaining colour polymorphisms in prey species. We report here the results of six experiments on wild birds feeding on 'populations' of two similar green 'morphs' of an artificial prey which had a single dark green stripe or were plain. Birds foraging on lawns were fed on one type and then given a choice of equal numbers of the two; they were then fed on the second type and again given a choice. In four experiments each training period lasted one day; in the remaining two experiments, five days. The results showed that birds tended to prefer the familiar prey - even after the shorter training sessions. Although training effects are not a prerequisite for apostatic selection we conclude that the results provide evidence for behaviour that could lead to the maintenance of prey polymorphisms in which morphs are differentiated by the presence or absence of inconspicuous patterns. D. L. Raymond and J. A. Allen, Dept of Biology, Univ. of Southampton, Southampton S09 3TU, England.