{"id":67,"date":"2009-02-24T09:44:00","date_gmt":"2009-02-24T13:44:00","guid":{"rendered":"http:\/\/web.colby.edu\/mainebirds\/2009\/02\/24\/67\/"},"modified":"2009-02-24T09:44:00","modified_gmt":"2009-02-24T13:44:00","slug":"67","status":"publish","type":"post","link":"https:\/\/web.colby.edu\/mainebirds\/2009\/02\/24\/67\/","title":{"rendered":""},"content":{"rendered":"

For the Birds: Bird Feeding Effects – Part II<\/span><\/span><\/p>\n

Gillian Robb, an Irish ornithologist, and several of her colleagues have recently published a review of avian responses to supplemental feeding in the journal Frontiers in Ecology and the Environment. I discussed some of their points in the last column and will continue that discussion in today\u2019s column.<\/p>\n

Providing supplemental food to breeding females may allow them to spend less time looking for food and more time incubating the eggs or dependent young. Such an effect has been clearly shown in a study of Australian reed warblers and is likely a general phenomenon.<\/p>\n

Given extra food, parents can either spend less time foraging for food to give their nestlings or use their extra time to find even more natural food for their young. In most species studied, parents simply spend less time looking for food rather than ambitiously trying to give their young even more food.<\/p>\n

Chicks given supplemental food were much more likely to fledge than chicks without access to extra food in nearly two-thirds of the studies Robb reviewed. Black-legged Kittiwakes show one of the most striking effects. Adults fed supplemental food over two years, fed in turn to their chicks, fledged twice as many chicks in their first year and three times as many in the second year as kittiwakes that were not given extra food.<\/p>\n

Given the difficulty of finding food for many birds, it is not surprising that supplemental feeding can alter the behavior of birds. Varied Tits (a chickadee relative) reduced their participation in winter mixed-species flocks when given extra food. Mixed-species flocks form when food is scarce and patchy.<\/p>\n

The authors cite some of my research on Black-capped Chickadees in the North Woods of Maine. By providing supplemental food, I found that winter territorial boundaries break down. As many as 10 different winter flocks used the same feeders over the course of a single day.<\/p>\n

Supplementary feeding may affect bird reproductive behavior. When House Sparrows were provided with extra food, the males stayed closer to their nests. Females cheating on their mates by mating with other males decreased because of the increased presence of the male.<\/p>\n

Providing food to birds can alter the distribution of birds over large geographic areas. The northward expansion of Northern Cardinals may have resulted, at least in part, from backyard bird feeding. In Finland, ornithologists strongly suggest that backyard feeding explains a tendency of birds to overwinter in Finland rather than migrate south.<\/p>\n

A contentious topic related to bird feeding concerns the degree to which birds become dependent on our handouts. In Finland, Great Tits feed most of the time from feeders and ornithologists suggest that these birds are so dependent on supplemental food that they could not survive without the freebies. So, feeding stations can be seen as ecological traps.<\/p>\n

However, a study in Wisconsin with Black-capped Chickadees failed to find such feeder dependency. A population of chickadees that had been fed for 25 years was deprived of extra food in one winter. Those birds survived at the same rate as other chickadee populations close by that had never been given supplemental food.<\/p>\n

Winter feeding can increase the density of resident birds in an area. These birds may stay in the area to nest during the summer, inflating the number of breeding birds. Jays and crows living close to humans take up to 75% of their food from human handouts. The local increase in these birds poses a threat to other songbirds because jays and crows are efficient egg predators.<\/p>\n

Bird feeding can have indirect impacts as well. The gathering of large numbers of birds at one place increases the likelihood of the spread of diseases. The bacteria Mycoplasma and Salmonella are particular threats. The increased risk of disease at bird feeders in the United Kingdom is so high that the Garden Bird Health Initiative was begun, which prescribes bird feeding practices to lower the risk.<\/p>\n

Some people that feed the birds are concerned that the high concentration of birds attracts birds of prey like Sharp-shinned Hawks or Cooper\u2019s Hawks. Happily, research has shown that birds frequenting feeders are not more likely to be killed by predators. Large groups of birds are vigilant; the approach of a predatory bird or mammal is usually detected by the many watchful birds at a feeder.<\/p>\n

We still have much to learn about the effects of bird feeding. Most studies have been conducted at a single feeder rather than at widely dispersed feeders, reflecting the distribution of households that feed the birds.<\/p>\n

Should we feed the birds? To date, we believe the benefits exceed the risks. So, keep those feeders filled!<\/p>\n

[Originally published on November 28, 2008]<\/p>\n\n

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For the Birds: Bird Feeding Effects – Part II Gillian Robb, an Irish ornithologist, and several of her colleagues have recently published a review of avian responses to supplemental feeding in the journal Frontiers in Ecology and the Environment. I discussed some of their points in the last column and will continue that discussion in […]<\/p>\n","protected":false},"author":146,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[1],"tags":[],"builder_content":"","_links":{"self":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/67"}],"collection":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/users\/146"}],"replies":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/comments?post=67"}],"version-history":[{"count":0,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/67\/revisions"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/media?parent=67"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/categories?post=67"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/tags?post=67"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}