Small species go hungry as bigger bullies dominate the bird feeder

Homeowners who leave food out may fuelling unnatural competition

BIRD feeders inadvertently favour pushy big birds like sparrows that knock little birds out of the way and may only be helping garden bullies, a study has found.

Gardeners spend around £200million a year on bird food, which helps some of Britain’s most beloved species get by in the harsh winter months and beyond.

But research by the University of Exeter and the British Trust for Ornithology (BTO) found that they may only be feeding larger species, which can fight for the most nutritious food.

It might also be bringing together species who would usually stay apart, the researchers warn.

“Bird feeding has become increasingly popular in recent decades,” said Prof Jon Blount, the senior author of the Centre for Ecology and Conservation on Exeter’s Penryn campus in Cornwall. “However, its impact is still poorly understood.

“Bird feeders create a concentrated food source that can result in more quarrels between individuals of different species, which we predicted would lead to the formation of a dominance hierarchy.

“Our findings show that larger, heavier species get better access to food – so if the aim of bird feeders is to benefit all species, we need to investigate ways to achieve this, such as different mixes of foods and feeder designs.”

Gardens have become a haven for many birds that have suffered from habitat loss and urbanisation, and some 48 per cent of households regularly leave food out to help garden visitors.

For the study, researchers watched birds at feeders placed at woodland edges and hedgerows on the Penryn campus.

Dominance ranks for each species were measured by recording any interaction between two individuals that resulted in one retreating from the food source.

They found larger species like house sparrows and greenfinches monopolised the best food and spent longer feeding than smaller birds.

Meanwhile, smaller birds such as blue tits and coal tits had to feed quickly and were left with lower-quality food.

Heavier bird species monopolised access to sunflower hearts – a food that had a “relatively short handling time”.

Lighter species were left with sunflower seeds with the hull intact – a food that takes longer to open and eat.

Dr Kate Plummer, of the BTO, said: “With more and more people feeding the birds in their gardens, it is more important than ever that we understand any implications this might have for the birds themselves.

“We know that during harsh weather, the food put out by homeowners can offer a lifeline but beyond this, the benefits might be more subtle, so it is interesting that our findings are less straightforward and that more work needs to be done.”

Earlier research showed that bird tables and feeders also spread illness by bringing species together that would never normally come into contact. For example,

trichomonosis, emerged in finches in 2005 but soon spread to gregarious seedeating species that visited garden feeding stations.

The paper was published in the journal PLOS One.