25 May 2010, by Sara Coelho
Birds shun organic seeds in favour of conventionally-grown grain when given the choice. This doesn't mean that organic foods are bad, say researchers; it's probably just that the birds find the more protein-rich conventional seed more satisfying to eat.
The findings come from the first of a set of long-term experiments designed to test bird preference for organic or non-organic foods. Previous lab studies suggested that birds and mammals are partial to organic meals, but Dr Ailsa McKenzie of Newcastle University questioned the methods used.
'The difference between organic and conventionally-grown seeds is not a matter of taste – it takes time for the birds to tell one from the other,' she says. 'Previous studies were too short and the birds did not have time to appreciate the difference between them.'
Although birds find conventional wheat more nutritious than organic seeds, organic farming remains a important and valid farming method.
McKenzie and Newcastle colleague Dr Mark Whittingham decided to see what happened when the birds were given enough time to learn.
In their first experiment, the team offered a group of 12 canaries a choice of organic and conventionally-grown wheat seeds. Then they sat back and patiently counted how many times the birds pecked at each bowl.
'Overall the birds preferred conventional grain over organic,' says McKenzie. During the 14 days of the experiment the canaries chose the non-organic wheat on average 66 per cent of the time. As the days passed and the birds learned the difference between the two foods, the preference for conventional wheat increased.
Over the next two winters they repeated the experiment in 47 gardens across Newcastle-upon-Tyne and Northumberland. The team offered resident birds a choice of organic and non-organic wheat seeds and measured how much grain was consumed daily from the two feeders. The experiment lasted for six weeks in the first winter and eight in the second, and, as before, the birds showed a strong preference for conventionally-grown seed.
But how do the birds tell the difference between grain from organic farms and wheat grown with the help of fertilisers and pesticides?
'It's not the taste, because the preference takes time to develop,' says McKenzie. So it must be something innate to the grain. Wheat from conventionally fertilised crops is often has a higher protein level. 'It is likely that after a while, the birds begin to sense that conventional wheat has more protein,' she says, adding that maybe the birds feel more satisfied with a diet rich in protein.
To test if the birds can learn to spot high-protein wheat, the team went back to the lab for a final experiment. They selected two types of wheat grown in the same conventional farm, but fertilised with different amounts of ammonium nitrate. The only difference between these types of non-organic grain was their protein level, which was higher in the over-fertilised crop.
'The canaries ate less low-protein than high-protein wheat throughout the trial,' says McKenzie, who reported the results in the Journal of the Science of Food and Agriculture.
McKenzie was keen to stress that even if birds find conventional wheat more satisfying than organic seeds, organic farming remains an important and valid farming method. 'Organic farming has been shown to have lots of benefits for biodiversity and the environment. Moreover, our study does not look at the potential health implications of a conventional versus organic diet,' says McKenzie.
Nor do the results apply directly to human diet, which is already overflowing with protein from sources such as meat or dairy. 'Unlike birds, we don't need to select conventional wheat for its protein content,' she concludes.