By Ben AvissBirds, such as great and blue tits, search for food in the morning but only return to eat it in late afternoon, scientists have found.The team believe the behaviour maximises their chances of avoiding predators during the day without starving to death overnight.
Researchers from the University of Oxford tracked the birds’ winter foraging movements using tiny tags.
All five of the studied species of songbirds behaved in the same way.
The results are published in the Royal Society journal Biology Letters
“Our results are important because they provide a new hypothesis for how animals forage,” said Damien Farine, lead author from the University of Oxford.
“They suggest that animals integrate the different risks they face into one strategy that can be applied to satisfy both their need to avoid predation and avoid risk.”
Scientists have been studying bird populations at Wytham Woods, Oxfordshire, UK since 1947.
Finding food becomes more and more relevant towards the end of the winter when large sources of food, such as beech mast, have become depleted.
The team knew from previous studies that, when the predation risk appears high, birds delay putting on fat until late in the day.
“In the 1970s, when there were almost no sparrowhawks, tits used to be much fatter [in winter], which helped them avoid the risk of starvation.
“When sparrowhawks returned [in greater numbers], the average body weight of great tits, for example, decreased,” Mr Farine told BBC Nature.
According to Mr Farine these birds had shifted from a strategy of being fat, to a strategy where they delayed putting on fat until late in the day.
“However, no one had previously thought to test how birds manage the need to find food so that they can ensure that there will be enough food left at the end of the day in order to put on the necessary amount of fat and survive the long winter nights,” he said.
Instead of simply idly waiting until the afternoon, birds were actively seeking out new sources of food to work out where their next meal was coming from.
Mr Farine said: “They can vary their strategy within the day in order to satisfy multiple needs, in this case avoiding predation but also finding ephemeral food.”
Food for thought
Mr Farine said he was hoping to test a number of questions that arose from these results.
Previous studies have shown that along the social ties, information about food sources are transmitted between individual birds within a population.
“We would like to test if individuals vary in their use of this social information over the course of a day. For example, if they have not gained good quality information in the morning, do they ignore it and search for their own food?” Mr Farine told BBC Nature.
“We would then like conduct further research on the afternoon and evening strategies in order to test whether the birds actually do remember what the best site was that they visited by placing different quality foods out for them to discover.” – BBC Environment
