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Garden birds found to shun organic

May 18, 2010
Courtesy of Newcastle University
and World Science staff

Wild gar­den birds pre­fer con­ven­tion­al bird seed to or­gan­ic­ally grown bird seed, ac­cord­ing to a study that calls in­to ques­tion the nu­tri­tional ben­e­fits of or­gan­ic food.

The research found that wild birds, un­swayed by the or­gan­ic la­bel, pre­fer the more pro­tein-rich, con­ven­tion­al food that will help them sur­vive the win­ter.

A bird visits a feed­er as part of a study by Ail­sa Mc­Ken­zie of New­cas­tle Uni­vers­ity in the U.K. and col­leagues. (Cour­tesy New­cast­le U.)


“Our re­sults sug­gest that the cur­rent dog­ma that or­gan­ic food is pre­ferred to con­ven­tion­al food may not al­ways be true,” said Ail­sa Mc­Ken­zie of New­cas­tle Uni­vers­ity in the U.K., who led the stu­dy. 

But she stressed that “this study is only look­ing at one as­pect of the or­gan­ic food de­ba­te. It does not take in­to ac­count the long-term health im­plica­t­ions of us­ing chem­i­cal fer­tilis­ers and pes­ti­cides” as­so­ci­at­ed with con­ven­tion­al food. Nor does it take into ac­count “the of­ten neg­a­tive en­vi­ron­men­tal im­pact of con­ven­tion­al farm­ing.”

The study is pub­lished May 18 in the Jour­nal of the Sci­ence of Food and Ag­ri­cul­ture

“Pro­tein is an es­sen­tial nu­tri­ent... and get­ting enough of it, es­pe­cially in win­ter, can be hard. We showed that when giv­en free choice, wild birds opt for the con­ven­tion­al food,” Mac­Ken­zie said. “The most likely ex­plana­t­ion is its high­er pro­tein con­tent.”

Glob­al de­mand for or­gan­ic pro­duce is grow­ing by an es­ti­mat­ed $6 bil­lion an­nu­al­ly. The or­gan­ic mar­ket now ac­counts for two to three pe­r­cent of all food pur­chased in Eu­rope and the Un­ited Sta­tes. Con­sumers buy or­gan­ic partly be­cause they con­sid­er it health­i­er. While this may be true, it’s not nec­es­sarily the only fac­tor go­verning food choice in an­i­mals, Mac­Ken­zie not­ed.

Mac­Ken­zie and col­leagues set up bird feed­ers in more than 30 gar­dens across north­ern Eng­land. Or­gan­ic and non-or­gan­ic wheat seeds, of the same va­ri­e­ty, were placed in ad­ja­cent bird feed­ers. The ra­te at which the birds ate the dif­fer­ent seeds was then mon­i­tored over six weeks. Half way through the ex­pe­ri­ment the feed­ers were swapped around. The ex­pe­ri­ment was repea­ted in a sec­ond win­ter with dif­fer­ent wheat sam­ples. 

In each case, birds were found to eat the con­ven­tion­al seed at sig­nif­i­cantly high­er ra­tes.

An anal­y­sis found the con­ven­tion­ally-grown seeds to have an av­er­age 10 per cent high­er pro­tein con­tent than the or­gan­ic seeds. Oth­er dif­fer­ences be­tween the sam­ples could­n’t ex­plain the birds’ pre­ferences, said the re­search­ers.

“Conventionally-grown crops tend to con­tain sig­nif­i­cantly high­er lev­els of pro­tein than those grown or­gan­ic­ally due to the ap­plica­t­ion of inor­gan­ic ni­tro­gen fer­tilis­ers in con­ven­tion­al farm­ing sys­tems,” Mac­Ken­zie said. “This makes our find­ings po­ten­tially ap­plicable across many food types and sug­gests the is­sues sur­round­ing or­gan­ic food are not as cut and dried as some might think.”


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Wild garden birds prefer conventional bird seed to organically grown bird seed, according to a study that calls into question the nutritional benefits of organic food. The three-year study found that wild birds, unswayed by the organic label, prefer the more protein-rich, conventional food that will help them survive the winter. “Our results suggest that the current dogma that organic food is preferred to conventional food may not always be true,” said Ailsa McKenzie of Newcastle University in the U.K., who led the study. But she stressed that “this study is only looking at one aspect of the organic food debate. It does not take into account the long-term health implications of using chemical fertilisers and pesticides” associated with conventional food, “or the often negative environmental impact of conventional farming.” The study is published May 18 in the Journal of the Science of Food and Agriculture, “Protein is an essential nutrient in the diet of all birds and mammals and getting enough of it – especially in winter – can be hard. We showed that when given free choice, wild birds opt for the conventional food over the organic, and the most likely explanation is its higher protein content,” MacKenzie said. Global demand for organic produce is increasing by an estimated $6 billion annually. The organic market now accounts for two to three percent of all food purchased in Europe and the United States. Consumers buy organic partly because they consider it healthier. While this may be true, it’s not necessarily the only factor governing food choice in animals, MacKenzie noted. MacKenzie and colleagues set up bird feeders in more than 30 gardens across northern England. Organic and non-organic wheat seeds, of the same variety, were placed in adjacent bird feeders. The rate at which the birds ate the different seeds was then monitored over six weeks. Half way through the experiment the feeders were swapped around. The experiment was repeated in a second winter with different wheat samples. In each case, birds were found to eat the conventional seed at significantly higher rates. An analysis found the conventionally-grown seeds to have an average 10 per cent higher protein content than the organic seeds. Other differences between the samples couldn’t explain the birds’ preferences, said the researchers. “Conventionally-grown crops tend to contain significantly higher levels of protein than those grown organically due to the application of inorganic nitrogen fertilisers in conventional farming systems,” MacKenzie said. “This makes our findings potentially applicable across many food types and suggests the issues surrounding organic food are not as cut and dried as some might think.”