20 February 2009

The late Mark Blacksell and late John Woodland worked tirelessly to recruit and encourage birdwatchers across Devon to participate in the national BTO Atlas by taking on tetrads for timed counts and to make a note of their casual records. In a special report for the Devon Birds website, National Coordinator DAWN BALMER reports on progress with the survey in Devon.

We are fast approaching the end of the second winter of the Bird Atlas and we are delighted with progress so far. Coverage in Devon is really good, but there is still plenty to do in terms of both Timed Tetrad Visits and filling in gaps in species lists for each 10-km square.

A measure of how well we are doing is to take a look at ‘species richness’. Based on the species lists from the last Winter Atlas (1981–1984), we have a good idea of how many species we should expect to find in each 10-km square. Of course, exact species composition may have changed (think of all the wintering Little Egrets we have now), but it’s a good starting point and will help direct volunteer effort to try and maximise the species list for each 10-km square.

The maps below show the 10-km squares in the BTO region of Devon (Figure 1) and the species richness in winter (Figure 2). This is worked out by looking at the proportion of the expected species list already achieved for each 10-km square. The 10-km square that needs most help is SS70 (Copplestone, Lapford Cross, Morchard Bishop area). The other priority 10-km squares that require help with casual birdwatching to help build species lists are: SS72 (South Molton area), SS74 (Lynmouth and the area inland), SY09 (Aylesbeare/Marsh Green area), SX44 (Penlee Point), SX94 (Inner Froward Point nr Kingswear), SY07 (Orcombe Point nr Exmouth) and SY38 (Humble Point nr Charton – a tiny bit of land in the 10-km square).

Figure 1 – Devon 10-km squares

Figure 2 – Species richness in Devon

It’s exciting to look at the provisional distribution maps to see how ranges are changing – both expanding and contracting. Many species have been well recorded across their range and the provisional maps look fairly accurate, but for other species there are still gaps. Are these gaps due to poor coverage or are the species not there anymore? Four provisional maps for winter are presented below: are these a true reflection of the status of the species in Devon? Can you put more dots on the maps?

Golden Plover are fairly numerous in Devon in winter with some important sites such as the Taw/Torridge Estuary, Tamar area, Dartmoor, Exmoor and the South Hams. The 1981–1984 Winter Atlas showed Golden Plover to be more widespread than currently recorded. Can you add a dot to the map?

Grey Partridge have contracted in range over the last 20 years and the changes between the two national breeding atlases showed huge losses in the South West of England. The provisional map for winter shows just a handful of records in Devon. Is this about right? The last Winter Atlas recorded Grey Partridges in South, North and East Devon.

The provisional winter map for Raven shows that the species has been recorded in virtually all 10-km squares in Devon – the most obvious gap in the middle is SS70 (Copplestone, Lapford Cross, Morchard Bishop area). Ravens have made an impressive expansion eastwards since the 1981–1984 Winter Atlas and also filled in gaps within their existing range.

It’s surprising how many Black Redstarts have been recorded between 1 November 2007 and 28 February 2008. Many of these will certainly be autumn passage migrants rather than true winter visitors. The last Winter Atlas showed a similar distribution across Britain and Ireland, although it looks as if there are now more records from West Wales and West Cornwall.

‘Bird of the Day’ on the Atlas homepage (www.birdatlas.net) randomly selects a species every day and it’s always worth a look to get a feel for some of the other species we are recording.

Take part

If you can spare a bit of time then we still need volunteers to take on Timed Tetrad Visits in SS44, SS75, SS74, SS73, SS51, SS49, SY18, SX84 and SX73. We’re also happy to accept further help in those 10-km squares where we have already reached the minimum level of coverage required. A tetrad requires two visits in the winter and two visits in the breeding season and then it is complete. The minimum requirement for each visit is one hour.

Help with Roving Records is needed in all areas but particularly the 10-km squares mentioned above. A useful feature on the Atlas website (in Data Home) is ‘Any Square Summary’ which will give you a list of all the species recorded in a 10-km square so far, so you can concentrate on filling in the gaps.

For all Atlas enquiries please contact Dawn Balmer at BTO. Email dawn.balmer@bto.org or telephone 01842 750050. If you need any more paperwork or help with the online facilities, do get in touch.