Edited by Stella Beavan and Mike Lock
Devon Birdwatching and Preservation Society, 2016
Hbk, 508pp; many colour photos, illustrations and distribution maps
ISBN 978-0-9556028-9-4, £46.99
In 1988, the Tetrad Atlas of the Breeding Birds of Devon was one of the first large-format atlases, setting new standards in the mapping and analysis of the distribution of birds at the tetrad level (see Brit. Birds 81: 672), and formed a template for several subsequent tetrad atlases.
The scope of Devon Bird Atlas 2007–2013, like so many of the current crop of county atlases, differs from the first in that it includes distribution maps for both the breeding season and the winter months. The fieldwork was carried out over six years, compared with nine for the previous atlas. These long survey periods are a reflection of the size of the county (1,858 tetrads) and the large areas of countryside remote from the bulk of the human population. Both books were published within three years of completion of the fieldwork, which is highly commendable given that all the effort is voluntary. Where the Devon Bird Atlas differs from other similar projects is that the breeding season is defined as March to September, and winter as October to February. Consequently, species that occur regularly every year are mapped, including passage migrants such as Wood Sandpiper Tringa glareola, the skuas and Yellow-browed Warbler Phylloscopus inornatus.
The book is a pleasing mix of fine photographs (of birds and habitats), maps and relatively brief texts, which generally include some description of species’ current range, statistics of change, and sometimes the reasons for those changes. A typical species account includes a large map of breeding distribution for 2007–13, with smaller maps of breeding distribution in the previous survey (1977–1985), and of abundance in both the breeding and the winter periods for 2007–13. Even some summer migrants (e.g. Garden Warbler Sylvia borin) have winter-period maps, for records in October or November. With the extended definitions of the seasons, very few species (e.g. Snow Bunting Plectrophenax nivalis) have just a winter abundance map, and passage birds have only abundance maps. The background colour for the county of Devon is green on the maps, with Dartmoor and Exmoor shown in grey – it is unclear whether this is land above a certain height, or the extent of the national parks. Occupation by tetrad on distribution maps is shown by a red circle (largest for confirmed breeding) or a pale pink circle for presence with no breeding evidence. I found the pink dots almost invisible against the green background. Abundance maps use squares but in seven different colours to represent counts with the same range values used for all species and for both seasons. Those for the breeding season are dark red to pale pink, and for winter purple to pale blue. Again, the pale colours are not obvious on the maps. Surprisingly, there are no change maps, and the decision to exclude them seems not to be explained in the book. Instead of repeating distribution from the previous Devon atlas, surely a change map would have given an opportunity to demonstrate differences between the two surveys more clearly? Overall change by breeding category is shown in a table for breeding species and the differences have been tested using a 2 x 2 contingency table analysis, which shows whether any change is statistically significant, a useful addition I have not seen used elsewhere. Most species are mapped at tetrad level, though a few of the more sensitive species, such as Hobby Falco subbuteo, Peregrine Falcon F. peregrinus and Woodlark Lullula arborea, only at 10-km square level; I was surprised to see Common Sandpiper Actitis hypoleucos (only four tetrads recording confirmed breeding) being one of these.
Humphrey Sitters, author of the first atlas, provides the preface and highlights some of the key findings described in the book. Of the 84 species whose breeding ranges have undergone substantial change, 61 have seen range contraction compared with 23 that show expanded ranges. Examples of species which are no longer almost ubiquitous include Common Cuckoo Cuculus canorus, Skylark Alauda arvensis, Common Starling Sturnus vulgaris and Yellowhammer Emberiza citrinella. Many of these changes are believed to be a result of changing agricultural practices, a consistent theme in other recent tetrad atlases. The fine detail of winter distribution for many species is revealing, especially where the birds occur mainly inland, away from well-watched sites. Thus Bramblings Fringilla montifringilla occur mainly in the south of Devon while Starlings are mainly in the north and west. Explanations for these observations are not immediately forthcoming but looking at the habitat maps in the introductory chapter on habitat types suggests (to me) a relationship with broadleaved woodland and improved grassland respectively. Since seven different habitat types are mapped by tetrad in an introductory chapter, it would have been nice to see some analysis of distributions against habitat. A few examples of species where the declines in the number of occupied tetrads in the breeding season surprised me are Eurasian Jay Garrulus glandarius and Common Whitethroat Sylvia communis (both extremely significant decline), and Common Buzzard Buteo buteo (significant decline). These declines are at odds with national trends but the atlas does not offer suggestions as to why there may be differences in Devon.
One of the innovations of the first Devon Atlas was the use of graphs to show the distribution of species by altitude. I was pleased to see this repeated (though for breeding species only), as it has been rarely copied by others. Tetrad-level information means that these simple graphs can reveal patterns not obvious from maps. Most of Devon (89%) lies below 200 m, though, so there are no real surprises. An opportunity to look for changes in the altitudinal distribution since the previous atlas has been missed. Rather than being shown with the species accounts, the altitude charts are included in an appendix alongside a site gazetteer, detailed climate data for the survey period and a full list of the birds in Devon up to October 2015. Other species recorded in the county in 2007–13 are included in a separate chapter at the end of the main species accounts.
With the introductory chapters including a review of the Devon environment, incorporating geology, weather and habitat types, and a history of bird recording in Devon, the whole book effectively describes the birds of Devon during the survey period, and is therefore an essential purchase for residents of the county or those with some connection to Devon. Unlike the first bird atlas of Devon, it is not groundbreaking, but is a worthy successor and can stand proud against the other county atlases which have followed the publication of Bird Atlas 2007–11.