Why?

How – What’s involved?

Targets

Mapping questions and answers

Progress so far

Other atlas sites of use

Timed Tetrad Visits = counts for abundance estimates

Roving Records = full lists for each tetrad, with breeding evidence in spring

To get an inventory of the birds we have in Cambridgeshire, and the British Isles, for comparison with past and future atlases. The timed visits are to get a measure of abundance that can be compared to other areas within the county and British Isles. The roving records are to get as complete as possible list of species for each 2km (tetrad) and 10km square.

There have been many changes in land use since the first national breeding atlas in 1968-72 and the results of the 1988-92 atlas show some of these effects, notably on species such as Cetti’s Warbler and Corncrake. County atlases for “Old” Cambs and Hunts were produced at the time of the last full atlas. Twenty years are up now so it’s time for another atlas. There have been two seasons of fieldwork so far and some changes are already obvious, in species such as Buzzard.

There was also a winter atlas in 1981-84 and the current winter atlas will no doubt show interesting differences – e.g. there were no records of Marsh Harrier in Cambs in the last winter atlas. Who knows what may have come or gone by 2028?

The next two seasons will build on the effort so far, filling in gaps, adding to existing lists and finding more breeding evidence.

There are two ways to contribute to the bird atlas: Timed tetrad visits and Roving records, see BTO website for methods.

Contact Louise Bacon (or at meetings) to sign up for tetrads or to ask further questions about the atlas: old Cambridgeshire and old Huntingdonshire show which tetrads have been allocated for timed visits so far.

Anyone can submit roving records for any tetrad so no need to sign up for that, just the timed visits.

These involve counting all birds while walking round a tetrad (2km square) in a known time - one or two hours as you decide.

The fixed time allows comparisons of the abundance of species between different areas. Two visits are needed per season – one Nov-Dec and one Jan-Feb for the winter season and then one Apr-May and one June-July for the breeding season. Breeding evidence should be recorded in the summer but isn’t the main aim – you shouldn’t stop too long to try to observe breeding behaviour but keep walking steadily around the square, covering the different habitats present. Winter surveys should avoid the period immediately after dawn or before dusk (so roost movements don’t confuse things) and breeding visits should be done early morning when most birds are singing and active.

Target coverage is eight tetrads per 10km square for the national BTO atlas and all 25 for the local atlas. The former still needs some extra tetrads in areas away from the main towns and cities. The latter is an aspirational target, but the closer we get the more complete picture of Cambridgeshire’s birds we’ll have, so all surveys help. All tetrad visits are used for the national atlas, so they help make that more accurate as well.

These are to try to get as complete a list as possible for each tetrad, with breeding evidence as appropriate.

Records can range from complete lists, broken down into each tetrad, from a local patch/nature reserve/ selected tetrads to single records of one species (e.g. Blackbird with food, Swallow visiting a nest, gulls on a flooded field). Getting confirmed breeding in every tetrad for every species that is breeding is not plausible so the target should be for probable (or confirmed) in each tetrad and confirmed for each 10km square. For some species (e.g. Spotted Crake, Grasshopper Warbler) confirmed breeding is unlikely to be recorded so probable breeding (birds holding territory) is sufficient for 10km square lists.

Roving records are important as some species will always be missed on timed visits, either by chance (I’ve managed to miss Wren on winter surveys), habitat (checking back gardens for winter Blackcaps isn’t too easy!) due to behaviour (e.g. owls) or inter-annual fluctuations (e.g. Waxwing, Brambling, Quail etc. or water birds during winter flooding). They also allow visits where obtaining breeding evidence is the priority – e.g. standing still in a wood observing birds carrying food, visiting nests or with fledged young – or during the day or evenings in the summer. Different species also show breeding evidence at different times so a July visit after a June timed visit may add to breeding evidence. Also, if you are not confident enough to take on recording everything in a tetrad just submitting roving records that you’re sure about is a valuable contribution.

Breeding evidence can be submitted outside April-July (e.g. Egyptian Geese with goslings in February, Lesser-spotted Woodpeckers and Little Owls on territory in March, Stock Doves at a nest in August etc.)

See here for a number of codes that should be used for breeding evidence. Note that the definition for code ‘T’ has been clarified to: “Permanent Territory presumed through registration of territorial behaviour (song etc) on at least two different days a week or more apart at the same place or many individuals on one day” – so birds singing against each other on a single day count.

Display or song flights count as ‘D’ except for Skylark (e.g. Whitethroat).

All evidence should be from suitable breeding habitat, so be cautious about things such as displaying wildfowl (e.g. Goldeneye) and juveniles that may have moved a considerable distance (e.g. Starlings and Grey Heron).

Records can be submitted online, either through BirdTrack or via the birdatlas website (registration required but that’s simple). Alternatively paper forms are available that can be sent to the BTO or dropped off with the club at indoor meetings for forwarding on. Submitting online helps other people see what has already been recorded and saves the BTO data entry costs.

Nationally the target is at least eight tetrads with timed visits per 10km square and a list (with confirmed breeding where possible) for each 10km square. In Cambs there are still some 10km squares that need more timed visits and roving records. This has to be the top priority for the next season.

For the local atlas the aim is for full 2km resolution – timed visits to every tetrad and roving records adding to the species list and breeding evidence for each tetrad. This appears plausible in and around Cambridge and Peterborough but perhaps aspirational further away from centres of population. Still, the more records that are submitted the more complete picture we’ll achieve of the current distribution of birds across Cambridgeshire. The final maps will show the level of coverage for tetrads without a record of a species. The longer the list for a tetrad, the more confident you can be that what’s not on the list really wasn’t there. All timed visits will also be used for the national atlas so any coverage over 8 tetrads increases the accuracy of the national atlas.

Picking a tetrad with few records is a likely way to check an area birders haven’t been – who knows what’s there?

I’ve seen something interesting, but which tetrad was I in?

The route I want to walk goes through different tetrads, where does one stop and the other start?

What routes are possible in areas that need extra records?

Tetrads are lettered A-Z (missing O), see here

Aerial image plus OS map and atlas, with dual cursor over each

Google map with grid reference and Tetrads marked and labelled

10km dragable OS1:50000 map, with photos

1:25000 map online giving grid references

If you’re still not sure which side of a tetrad boundary you were then it’s likely that the habitat continues across the boundary so the record is representative of both tetrads – take an educated guess if necessary, it’s better than not having a record submitted at all.

Owning the local OS 1:50000 or 1:25000 map is recommended, mine are annotated with pencil crosses marking the corners of tetrads.

Progress has been good, especially in and around the towns. More coverage is needed pushing out into the Fens more though and there are gaps to fill, lists to extend and breeding evidence to find in all areas. See allocations in Cambs and Hunts

Lists for each tetrad are available once you are logged into the atlas website (registration is easy). These are updated as soon as data is entered onto the site. Printing these off for an area that already has some records is an efficient way noting extra species/breeding evidence.

Lots of answers at the website of the Hampshire Ornithological Society

but note Cambs is not requiring two-hour visits – one or two hours for timed visits as you decide.

A possible way of displaying results at the website of the Beds Bird Club

Personally I’ve found atlasing to be extremely enjoyable so far. It’s got me into new areas, turned up some good birds and I’ve felt far more ‘in tune’ with the breeding season and changes in behaviour of different species this year than ever before. Apart from anything else, it’s motivation to find more birds and observe them a bit longer to see what they’re doing, and surely that’s a good thing.

Hugh Venables October 2009