They are famed for feasting on bird tables and coaxing cream from milk bottles ... now research reveals that the blue tit’s diet is nothing short of a woodland feast! The full extent of this much-loved garden bird’s diet has long been a puzzle to ornithologists, but a new study reveals that their food choices are remarkably varied. Diet Analysis Image Blue Tit - Image Credit: Gergana Daskalova Scientists have found that adult blue tits can devour more than 400 different types of prey prior to their springtime breeding season – a time when most trees are bare and food appears to be scarce – with moth caterpillars a particular favourite. Previous studies had shown that blue tits feed mostly on invertebrates, but most methods used to analyse their diet were only able to identify broad groupings of insects, such as caterpillars. Now a team, led by the University of Edinburgh, has used the latest genetic identification techniques to catalogue 400-plus different types of prey. Biologists examined DNA extracted from nearly 800 faecal samples, collected from blue tits’ nestboxes across 39 Scottish woodlands. As well as moth caterpillars – flies, wasps, beetles and spiders were popular items on the menu. Among the most common finds were species that feed on birch and sycamore buds, some of the first trees to come into leaf in spring. Breeding Season Cue Scientists were, however, surprised to find a prevalence of winter moth caterpillars in the birds’ diet – as these leaf eaters are not usually observed until early summer and not during March to April when most of the sampling took place. The team speculate that the blue tits may use the first appearance of these caterpillars as a cue to start their breeding season, because the more fully grown caterpillars of this species are known to make up a large portion of their chicks’ diet. Further examination of the new diet data revealed the tits’ diet becomes richer as spring progresses. Over the course of spring the type of species consumed changes and also varies geographically – from lowlands to uplands. It’s been fascinating to see how modern genetic technology can provide us with rich insights into the diet of these birds and to see how this changes, depending on where they are and the time of year. Dr Albert PhillimoreChancellor’s Fellow at the Institute of Evolutionary Biology, University of Edinburgh It is rewarding to see how applying DNA methods can help reveal the secret life of birds that behavioural observations would otherwise miss. Dr James NichollsCo-author, now of the Australian National Insect Collection Our knowledge of bird diet, even for common species like the blue tit, has barely advanced for decades. New genetic techniques like we used in this study will revolutionize our knowledge of bird diet, allowing us to fully understand what birds eat over the year and to help us ensure these prey remain available to them. Dr Malcolm BurgessRSPB Centre for Conservation Science The study, published in the journal Molecular Ecology, was carried out in partnership with the Centre for Research in Animal Behaviour at the University of Exeter, and the RSPB Centre for Conservation Science. The study was funded by the Natural Environment Research Council and the Royal Society. Related Links Gradients in richness and turnover of a forest passerine's diet prior to breeding: A mixed model approach applied to faecal metabarcoding data, Molecualr Ecology Albert Phillimore's Group Publication date 14 Apr, 2020
