The use of supplementary foods by Australian magpies Gymnorhina tibicen: Implications for wildlife feeding in suburban environments

Abstract

The provision of foods to wild birds is an extremely common practice among householders throughout the Western world. Nonetheless, concerns over potential impacts of the practice are currently being raised, including the possibility that some species may become reliant on human-provided food. We compared the foraging and breeding ecology of pairs of fed and unfed Australian magpies Gymnorhina tibicen living in suburban environments in Brisbane, Queensland, Australia. Detailed behavioural observations of both foraging and chick provisioning were made for males and females of both groups throughout the breeding season. Natural foods dominated the diets of both fed and unfed magpies, making up 76% and 92% of all items consumed respectively. During the morning, fed magpies obtained fewer food items during ground foraging than did unfed birds, apparently because they visited suburban feeding stations more often during the early part of the day. At other times, the amount of food items obtained during foraging was similar for both fed and unfed birds. Magpies utilizing suburban feeding stations started all breeding activities significantly earlier than unfed magpies, except during the fledgling phase. Both fed and unfed magpie parents provisioned their chicks predominantly with natural food. Magpies were not reliant or dependent on supplementary food provided by wildlife feeders at any time during the breeding season. Although many magpies did utilize suburban feeding stations extensively, they continued to forage for and provision their chicks with natural food.

An appetite for connection: why we need to understand the effect and value of feeding wild birds

“…These include the spread of disease, nutritional imbalances, enhancement of introduced or unpopular species, increased aggression, the creation of 'ecological traps', increases in unpopular species, including vermin, and, most frequently mentioned, the possibility of dependency on anthropogenic foods (Anderson et al 1997;O'Leary and Jones 2006). (Only some of these concerns are further discussed here; see Orams 2002, Ishigame et al 2006 for further discussion.)…”

“…Toms 2003). However, several recent studies looking specifically at this issue have found that a variety of species (including suburban Australian Magpies, British tits and Scrub Jays (Aphelocoma coerulescens) (Cowie and Hinsley 1988;Fleischer et al 2003;O'Leary and Jones 2006)), all with easy access to anthropogenic foods, used only small proportions of this food, but especially so when feeding their chicks. Most impressive of all, a population of North American Black-capped Chickadees (Poecile atricapillus) studied over several harsh winters in Maine showed no dependency on feeders and survived even when the feeders were suddenly withdrawn (Brittingham and Temple 1992).…”

Garden Bird Feeding: Insights and Prospects from a North-South Comparison of This Global Urban Phenomenon

“…As well as differences in avian community composition at feeders of Northern and Southern Hemispheres (Table 1), there are major differences in the types of food supplements provided, especially in Australia where meat is routinely fed to populous species such as Australian magpies, butcherbirds Cracticus spp., and kookaburras (Alcedinidae) that are all relatively large species and abundant in urban landscapes (O'Leary and Jones, 2006;Jones, 2011). The most commonly provisioned form of meat is raw beef mince (or ground beef), presumably because it is relatively inexpensive and readily available, although pieces of sausage, salami, ham, bacon, and cooked chicken are also provided (Ishigame and Baxter, 2007).…”

“…In their study of wintering black-capped chickadees in Wisconsin in the US, Brittingham and Temple (1992) found that a population supplied with supplementary food for 25 years had an identical survivorship to that of an unfed (control) population nearby. In Australia, adult Australian magpies continued to provide natural foods to their nestlings even when large supplies of favored foods were readily available (O'Leary and Jones, 2006). There are numerous other studies from a wide variety of species that strongly suggest that in the vast majority of cases individuals that visit feeders do so in rather a sporadic fashion with the diet comprising mainly natural food sources (e.g., Harrison, 2010;Robb et al, 2011;but see Sauter et al, 2006).…”

“…One could envisage that feeding might result in males guarding their social mates more intensely, resulting in reduced incidents of broods containing extra-pair young (EPY) and reduced proportions of broods containing EPY (e.g., O'Brien and Dawson, 2011); equally, the opposite may be just as likely with feeding resulting in better-fed males and females of social pairs seeking out more extra-pair copulations (EPCs) with the outcome being greater incidents of broods containing EPY and greater proportions of broods comprising EPY (e.g., Hoi-Leitner et al, 1999). To the best of our knowledge, no urban study has tested such hypotheses although Smith (2011) provided food supplements to a woodland population of birds throughout the spring and early summer.…”