The maps are provisional distribution maps, produced from records submitted to the BTO (Bird Atlas 2007-11 and BirdTrack) during the 2008 – 2010 breeding seasons. 

All records with breeding codes are allocated to one of the following categories:

Large dot = confirmed breeder e.g. Adult carrying Faecal sac or Food for young (FF)

Medium dot = probable breeder e.g. Permanent Territory (defended over at least 1 week) or 2+ birds singing against each other on a single date (T)

Small dot = possible breeder e.g. Singing male present in suitable breeding habitat on one date (S)

A full list of breeding codes can be viewed on the BTO website: http://www.bto.org/birdatlas/taking_part/bevidence.htm

A card containing the codes can also be obtained from the GM Atlas organisers. It is important to note that records submitted without breeding codes can not be used in the production of the distribution maps.

Statistics:

The tables on the maps compare the results from Breeding Birds in Greater Manchester (BBGM), for which the fieldwork was carried out from 1979 to 1983, with the records submitted to the BTO from the 2008-10 breeding seasons: 

The above example, for House Sparrow, shows that in BBGM the species was recorded in 305 tetrads (2km squares) out of the 329 surveyed i.e. 93% of all tetrads. The species was a confirmed breeder in 292 tetrads i.e. 96% of the occupied tetrads, a probable breeder in 8 tetrads (3%) and a possible breeder in 5 (2%). The comparative figures for the first three years (2008-10) of the new GM Atlas are shown in the column GM Atlas 2008-10.

Acknowledgements:

Many thanks to Mark Yeates of MapMate © for providing instructions which enabled me to produce the maps.

Digital Maps licensed from © Bartholomew 2003

Steve Atkins, April 2010

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