British Trust for Ornithology (BTO)

BTO Volunteers

The British Trust for Ornithology (BTO) has existed since 1933 as an independent, scientific research trust, investigating the populations, movements and ecology of wild birds in the British Isles, and increasingly, elsewhere.

The BTO aims to deliver objective information and advice, through undertaking impartial research and analysis, about birds, other species and habitats, to advance understanding of nature.  This can be used to inform policies and evidence-based decisions that impact on the environment such that future generations can benefit from a healthy and wildlife-rich environment.

The BTO undertakes a wide range of research on birds. Much of this is based on long-term monitoring schemes but other research projects investigate the conservation and other applied topics relating to birds. The BTO undertakes research that is often based on a partnership of volunteers and professional fieldworkers, and while the focus has been on British and Irish birds, collaboration on international projects is increasing.

The BTO has a number of key science areas, one of which is climate change, and a suite of research projects that investigate the impacts of climate change on bird populations, particularly formal reviews or analysis and modelling of long-term datasets have already been undertaken.  In addition to research findings, the BTO has provided advice to aid policy development by Government, and international (e.g. Convention on Migratory Species) and national bodies (e.g. Statutory Conservation Agencies).

Several BTO data sets will contribute to BICCO-Net, including the Breeding Birds Survey (and its predecessor, the Common Birds Census) and the Wetlands Birds Survey.  These are long-term and large-scale surveys (e.g. the Breeding Birds Survey has over 3,000 survey squares covered annually) with a broad geographic coverage and thus provide a powerful data set to analyse potential impacts of climate change on the population trends and distributions of birds.

Swallow

BTO Climate Change Research
BTO climate change research includes investigations of relationships between range, abundance and climate, the potential effects of sea level rise on coastal bird populations and the demographic mechanisms through which climate will affect abundance. BTO research has also been important for demonstrating how spring weather is already bringing about earlier arrivals of migrants and earlier egg-laying in many species.

Whitethroat nest

Using Nest Record Scheme data, Crick et al. (1997) demonstrated that 51 of 65 species tended to nest earlier during the period from 1971-1995. Twenty (31%) of the 65 species showed statistically significant trends towards earlier laying over the past 25 years. Species include: Oystercatcher, Curlew, Redshank, Dipper, Wren, Long-tailed Tit, Nuthatch, Starling, Tree Pipit, Redstart, Whitethroat, Blackcap, Wood Warbler, Chiffchaff, Willow Warbler, Magpie, Chaffinch, Greenfinch and Corn Bunting. For seven of the most widespread species, the trends in laying dates can be accounted for purely by the trends in temperatures and for 10 others, temperature and rainfall account for much of the changes (Crick & Sparks 1999). It is not yet known what the implications of these changes for birds will be. They may be beneficial because early fledglings often survive better than later nestlings. However, if birds become out of synchrony with their food supply or if they get hit by bad weather later on the spring, then the early nesters will suffer, perhaps decreasing overall productivity.

Wren

The BTO has also been involved in developing the set of Government Indicators of Climate Change in the UK, which were announced in June 1999 (Cannell et al. 1999). There are three bird indicators among these. The first is from the BTO's Nest Records Scheme: the laying dates of Chaffinch and Robin; both of which are strongly related to spring temperatures. The second is the population change of the Wren, as measured by the BTO's Common Birds Census. Wren numbers fluctuate widely, mainly due to high mortality in severe winters. Small bodied birds are particularly prone to prolonged spells of cold, wet, snowy or frosty weather because they cannot obtain enough food to maintain body temperatures. Big population declines have occurred after severe winters such as 1962/63, 1978/79 and so on. It is expected that Wren populations will not increase indefinitely if winters become progressively milder, but they will tend to stabilise at a relatively high level. The third bird indicator is the arrival date of Swallows, as measured by the daily records of birds seen at British coastal Bird Observatories..

References
Cannell, M.G.R., Palutikof, J.P. & Sparks, T.H. (Eds) (1999) Indicators of Climate Change in the UK. DETR & NERC, London.

Crick, H.Q.P., Dudley, C., Glue, D.E. & Thomson, D.L. (1997) UK birds are laying eggs earlier. Nature 388: 526.

Crick, H.Q.P. & Sparks, T.H. (1999) Climate change related to egg-laying trends. Nature 399: 423-424.