The Hertfordshire Bird Atlas
Between November 2007 and July 2012 the Herts Bird Club collected data to produce a new county bird atlas, surveying all 491 tetrads (2km x 2km squares) that include part of the county. It covered both the breeding season and the winter period and alongside, and used the same methods as, Bird Atlas 2007-11 - the British Trust for Ornithology / BirdWatch Ireland / Scottish Ornithologists Club atlas of the birds of the whole of Britain and Ireland. To achieve complete coverage at the tetrad scale in Hertfordshire it was extended for a fifth winter and breeding season.
The populations and distributions of Britain's birds are in a constant state of flux, as changes in the habitat and climate impact all aspects of their lifecycle. Only by monitoring where, when and in what numbers are our birds using the variety of habitats and resources within the county can we hope to understand these impacts.
Annual monitoring schemes, such as the BTO/RSPB/JNCC Breeding Bird Survey (BBS) operate by counting birds in randomly selected squares and provide yearly measures of population change. At the county level this gives only a broad indication of the changes in a relatively small number of species. Atlas projects complement the BBS by providing comprehensive information on the distribution of birds, covering far more squares than BBS.
This new Hertfordshire atlas was the first systematic assessment of the distribution of birds in the county at the tetrad scale in winter and the third breeding season atlas.
On this website you can find distribution maps from this latest project as well as those from previous atlas fieldwork in the county. These include the tetrad scale breeding status maps from atlases carried out from 1967-73 and 1988-92 and 10km square distribution and relative abundance maps from the 1981/2-1983/4 winter atlas. Also presented are breeding season change maps showing how the distributions have altered between successive breeding season atlas periods. During the latest project, Timed Tetrad Visits of one or two hours were carried out in all tetrads and the winter and breeding seasons and results of these are shown as relative abundance maps.
Many of the maps have been included in the 2015 publication Birds of Hertfordshire, but with the exception of a few species sensitive to disturbance, everything is included here, providing a rich resource to help understand the birds of Hertfordshire.