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i woodland 
vestigate if 
sed in these 
techniques can be obtained from air 
photographs, and therefore, used to predict 
bird carrying capacity. A bird census was 
conducted in Saltswells Wood in 1983 by 
Harrison and Normond. These local 
ornithologists identified the bird species 
which were breeding, their numbers and the 
approximate location of their territories. 
This field data was used as the control in 
this analysis. 
One of the simplist and most common 
variables used for prediction is area of 
woodland. This relationship was first 
suggested by Arrhenius 1921. Woolhouse 1983 
and Moore and Hooper 1975 have both conducted 
studies in British woodlands suggesting a 
linear relationship between the number of 
bird species present and the area of 
woodland. 
CL ; 
if) / 
LL ; 
O 
O 
z 
AREA 
Hypothetical species-area curve 
S=cA z 
AREA (ha) 
Species-area curve on a logarithmic 
scale lnS=clnA z 
from Woolhouse 1981 
FIG 3. 
The area of the classifed habitat types 
was the major variable to be investigated. 
The area information was obtained by using a 
Hewlett Packard digitizer connected to a BBC 
micro computer using a digitising program. 
The first stage was to identiy a list of 
bird species which were likely to be found 
breeding in Saltswells wood and relate their 
nesting and feeding requirements to the 
classification categories identified. 
Fifty-seven species commonly found in 
woodlands of a similar size and found 
breeding in the West Midland were earmarked. 
These birds were allocated one or more of the 
classification categories using the 'Handbook 
of British Birds' (Witherby et al 1965). For 
example a Blackbird is likely to be found 
breeding and feeding in categories 
34/43/44/45, that is, in deciduous shrubby 
habitats. Some bird species are limited to 
a single category such as the Wood Warbler. 
This species was only allocated closed 
deciduous woodland - 31. Other species need 
areas of woodland and grassland to fulfil all 
their requirements. The system allowed for 
this, for example the Common Crow needs 
32/33+51/52/53/58, that is, open deciduous 
woodland for nesting and grassland areas for 
feeding. As some species have similar 
requirements 32 habitat patterns were 
identified for the 57 species. 
The equations relating bird species numbers 
to areas of woodland suggested by Woolhouse 
and Moore and Hooper were investigated. 
Different habitat combinations and their 
corresponding area totals were used in these 
equations to identify which, if any, habitat 
combination produced a result similar to 27 - 
the actual number of bird species found 
breeding in the area by the control study. 
For results see Table 1. 
1 Woolhouse equation = 
In S = 0.227 In A + 2.632 
2 Moore and Hooper equation = 
In S = 0.271 In A +- 0.26 
Where In S = Natural log of the number of 
species 
In A = Natural log of area 
Table l.The relationship between woodland 
area and the number of bird species. 
Estimated number of species 
Area (ha) 
Eq. 1 
*1 
Eq. 2 
*2 
Reserve 
40.2 
32.2 
+5.2 
2.1 
-24.9 
Hab. 31 
14.4 
25.66 
-1.34 
1.6 
-25.4 
Hab. 34 
7.0 
21.59 
-5.4 
1.23 
-25.7 
Hab.31+34 
21.4 
27.84 
+ 0.84 
1.76 
-25.2 
Hab. 43,44, 
45, 
10.65 
23.8 
-3.2 
1.46 
-25.5 
Hab.31,34, 
30.56 
+3.56 
1.97 
-25.0 
43,44,45 
32.1 
* = the difference between the actual number 
of species,27 and the predicted number. 
There is a large discrepancy between the 
number of bird species predicted by the two 
equations. The Moore and Hooper equation 
obviously under estimates the number of 
species expected in this area therefore only 
the figures produced by the Woolhouse 
equation were considered. 
Of the different combinations of habitat 
units the total area of 31 and 34 provides 
the most accurate estimate of the number of 
bird species. Two apparent conclusions can 
be drawn.