Guernsey Wader Counts
On a designated day each month the teams of observers visit all ten sectors at, or around, high tide and counts the birds present. The observer also notes any causes of disturbance (e.g. walkers, dogs, aircraft, vehicles etc - the list is endless!) and also the impact of that event in terms of the severity of the impact on the birds. These data are collated and sent to the BTO.
Standard methods are used to work out an 'index' of abundance for
each species in each winter where there is enough data. In essence
this is really the same as working out the average number of birds
using a site over a winter and scaling is accordingly. In the analysis
carried out here we present the data for the winter period (defined
here as October to March inclusive) and the graphs etc are based on
the average number of birds counted each month within that period.
Where missing counts occur we 'impute' an estimate of the numbers present.
This is based on the normal count for that site in that month and it
is scaled appropriately according to whether there has been a general
increase/decrease at other sites. See here for
further details of methodology and statistical analysis.
Copyright © La Société Guernesiaise 2008. All rights
Candie Gardens, St Peter Port, Guernsey GY1 1UG, Channel Islands.