Habitat codes

The habitat coding system, as used for all bird surveys organised by the BTO, follows a straightforward hierarchy, with a letter for the primary habitat type and a number giving more detail. Observers could use as many habitat codes for each species as they felt appropriate. It was emphasised that the habitat is determined mostly by where the birds find their food, rather than the nest-site, and that it is helpful to look at the habitat from the birds’ point of view.

A Woodland
A1 Broadleaved
A2 Coniferous
A3 Mixed (10% of each)
A4 Broad-leaved - water-logged
A5 Coniferous - water-logged
A6 Mixed - water-logged            

B Scrubland
B1 Regenerating natural or semi-natural woodland
B3 Heath scrub
B4 Young coppice
B5 New plantation
B6 Clear-felled woodland with or without new saplings
B7 Other

C Semi-natural grassland / marsh
C2 Grass moor (unenclosed)
C3 Grass moor mixed with heather (unenclosed)
C5 Other dry grassland
C6 Water-meadow/grazing marsh
C7 Reed swamp
C8 Other open marsh
C9 Saltmarsh

D Heathland and bogs
D1 Dry heath
D2 Wet heath
D3 Mixed heath
D4 Bog
D6 Drained bog
D7 Bare peat

E Farmland
E1 Improved grassland
E2 Unimproved grassland

E3 Mixed grass/tilled land
E4 Tilled land
E5 Orchard
E6 Other farming

F Human sites
F1 Urban
F2 Suburban
F3 Rural

G Water bodies (freshwater)
G1 Pond (less than 50m2)
G2 Small water-body (50-450m2)
G3 Lake/unlined reservoir
G4 Lined reservoir
G5 Gravel pit, sand pit, etc
G6 Stream (less than 3m wide)
G7 River (more than 3m wide)
G8 Ditch with water (less than 2m wide)
G9 Small canal (2-5m wide)
G10 Large canal (more than 5m wide)    

H Coastal
H1 Marine - open shore
H2 Marine shore - inlet/cove/loch
H3 Estuarine
H4 Brackish lagoon
H5 Open sea

I Inland rock
I1 Cliff
I2 Scree/boulder slope
I4 Other rock outcrop
I5 Quarry
I6 Mine/spoil/slag heap

J Miscellaneous

The missing numbers (B2, C1, etc) are for specialised habitats not found in the county – chalk downland, breckland, machair, limestone cliffs and caves. After the first year of fieldwork, we added three further farmland codes:
E7 Farmland – stubble (the remains of last season’s crop left in the ground, not ploughed)
E8 Farmland with hedge – taller than about 2m (a little above head height)
E9 Farmland with hedge – shorter than about 2m