Although many of us provide food for garden birds, especially in winter, we are still only in the early stages of understanding exactly how this affects wild bird populations. One possibility is that winter food enhances birds’ ability to invest in future reproduction. However, it is likely that the type of nutrients a bird receives from supplementary food will be an important factor in determining whether this is the case. A new study by scientists at the University of Exeter, in collaboration with the BTO and the University of Turin, has shown exactly that. In a three year study of woodland Blue Tit populations, researchers examined the consequences of providing different winter food supplements for egg production. Their results showed that provisioning with fat alone resulted in smaller relative yolk mass, and reduced yolk carotenoid concentrations in early breeders. This suggests that females which utilised a fat-rich diet in winter were less able to acquire some of the important resources needed to form yolk during egg production. However, the addition of vitamin E to the fat mitigated the negative effects of a fat-rich diet. It is thought that this may be because, as an antioxidant, vitamin E provides protection against oxidative damage which could result from increased metabolism after eating fatty foods. These findings suggest that birds require a balanced diet, much like we do, to aid their reproduction, and it underlines the importance of considering the nutritional value of provisioned foods. This study highlights that much more research is needed to fully understand the impacts of winter feeding, in particular how it affects individual survival.

With European member states committed to obtaining 20% of their energy from renewables by 2020, the number of offshore wind, wave and tidal developments is increasing, potentially putting pressure on marine life. Seabirds could be affected in many ways, including through loss of foraging habitat, and collision with wind turbines. In a new study by the University of Liverpool, BTO and Alderney Wildlife Trust, GPS tags were deployed to examine how breeding Gannets on Les Etacs, Alderney, used their marine environment in early June 2011. The results showed that an individual’s foraging movements on consecutive trips away from the colony were consistent in direction and maximum distance travelled. Gannets visited nine sites earmarked for offshore renewables, suggesting these birds could be affected by development in these areas. Furthermore, these sites fell in three different territorial waters – those of France, the United Kingdom and the Channel Islands – illustrating how the impact of such developments needs to be considered at an international level for highly mobile species. As data were only collected for up to five days per bird, Gannets' movements over the course of the breeding season (and indeed the year) could bring them into contact with an even greater number of offshore developments. Since tracking technology is becoming cheaper, longer lasting, more accurate and easier to use on a wide range of species, such studies could form an integral part of the environmental impact assessment process for marine renewable developments.