Conserving Ugandan birds: land sharing or sparing?
Increases in human population and per capita consumption are placing growing pressures on ecosystems as agricultural demands escalate. This has led a debate about how best to farm for both high yields and biodiversity. Two contrasting models have been proposed: “land sharing”, where low-yield farming enables biodiversity to be maintained within the agricultural landscape, and “land sparing”, where high-yielding agriculture is practiced, requiring a smaller area of land to attain the same yields and therefore leaving greater areas of natural habitat untouched.
A new study led by the BTO has examined these two models in southern Uganda. The population densities of 256 species of bird were measured, along with crop yields and farmers’ income. Most birds were found to fare better under land sparing, especially those species with smaller geographical ranges, which are more likely to be of conservation concern. However, the authors suggest that high-yield farming can only be effective in delivering land sparing if combined with strong measures to protect natural habitats, other ecosystem services and human livelihoods.
Avian pox: a new infectious disease in British tits
New collaborative research has used information collected by BTO Garden BirdWatch volunteers to document the emergence and spread of a severe form of avian pox virus in British tits, especially Great Tits. The disease, which typically leads to unsightly growths on a bird’s head, was first reported in Sussex in 2006, and has spread north and westwards since. Although birds can recover from the virus, the lesions it causes may impair their vision and ability to feed, as well as leaving them susceptible to secondary infections and predation. The disease is thought to be spread by biting insects, leading to a peak in incidence in late summer after warm wet weather when insect population densities are high.
This study illustrates the power of collaborative research and value of citizen science in characterising and understanding wildlife diseases. It also underlines the importance of continued vigilance and reporting of illnesses in wild animals, as where avian pox and other emerging diseases (such as finch trichomonosis) lead, others may follow.
Wandering mariners: Gannets and offshore renewables
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. 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 Gannets breeding on Alderney use their marine environment. Gannets visited nine sites earmarked for offshore renewables, suggesting these birds could be affected by development in these areas. 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. 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.
Finch trichomonosis: emergence and spread
Finch trichomonosis has caused epidemic mortality in Greenfinches and Chaffinches across the British Isles since its emergence in 2005. A new study, which uses data from GBW, GBFS and BBS, shows that the British population of breeding Greenfinches has fallen from approximately 4.3 million to 2.8 million birds, and that the number of Greenfinches visiting gardens has also halved during this time. Chaffinches have been less severely affected. The study suggests that trichomonosis might have jumped to finches from Woodpigeons at shared feeding sites. This work has important implications for managing the on-going impact of the finch trichomonosis epidemic, and for assessing the likely effect of any future wildlife disease outbreaks.
Stepping stones to the north
A new study involving BTO has shown how birds, insects and spiders have used nature reserves and areas protected for wildlife to expand northwards in response to climate change and other factors. Using data from volunteer recording and national monitoring (including BTO surveys) from the 1970s onwards, the researchers showed that species disproportionately colonised protected areas in their northward expansion. These sites were approximately four times more likely to be colonised than would be expected given their availability in the wider countryside. Three key vulnerable birds, the Bittern, Woodlark and Dartford Warbler were significantly more likely to be associated with protected areas in newly colonised areas than would be predicted by chance alone. As many species will need to shift their distribution to respond to climate change, this study underlines the vital long-term importance of protected areas in conserving biodiversity.