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Birds At Bird Feeder
New research has shown that the pecking order of garden birds is determined by their size and weight.

Scientists from the University of Exeter and the British Trust for Ornithology (BTO) found that larger species like house sparrows and greenfinches monopolised the best food at bird feeders and spent longer feeding than smaller birds, such as blue tits and coal tits, who had to feed quickly and were left with lower-quality food.

The researchers say the findings have important implications for using bird feeders as a conservation method.

Senior author Professor Jon Blount, of the Centre for Ecology and Conservation on the University of Exeter's Penryn Campus in Cornwall, said, “Bird feeding has become increasingly popular in the UK and throughout much of the world in recent decades.

"However, its impacts are still poorly understood. Bird feeders create a concentrated food source which 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."

The team observed birds at feeders placed at woodland edges and near hedgerows on the Penryn Campus. The found that heavier species of birds monopolised access to sunflower hears, a food that can be eaten relatively quickly.

Lighter species were left with sunflower seeds with the hull intact, which takes longer to open and eat and therefore drains more energy.

Heavier birds also pecked at a lower rate, while small ones pecked quickly to make the most of their limited time at the feeders.

Joint first author 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 foods 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 to fully understand garden bird feeding."

Dominance ranks for each species were measured by recording any interaction between two individuals that resulted in one retreating from the food source. The bird that stayed was classified as the ‘winner’ ie more dominant, and the one that left was classified as the ‘loser’.

Although the ranking results do not show the ten species in exact order of weight there is a strong correlation between weight and dominance.

The two heaviest birds (based on average weight) were rated most dominant, house sparrow (27.3g) and greenfinch (27.7g), while the two lightest, blue tit (10.9g) and coal tit (9.1g), were bottom of the list.


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