Survey – Sussex Winter Bird Survey

Sussex Winter Bird Survey

 

Results from the BTO Breeding Bird Survey (BBS) in Sussex have been shown to be extremely valuable, providing much information about population trends of breeding birds. In order to obtain similar information about winter bird populations in Sussex, the Sussex Winter Bird Survey (SWBS) was started in November 2011 and will be repeated annually. The SWBS is an entirely local initiative, and summary results will be provided to all participants and published in the Sussex Bird Report. It is hoped that the SWBS will after a period of several years provide information about annual fluctuations of common wintering birds. For example, the survey might be particularly useful for monitoring wintering numbers of fieldfares and redwings in Sussex.

The basic design of the survey is that current BBS volunteers survey their normal BBS squares twice during the winter. However, the survey can very easily be extended by selecting extra random 1-km squares so that other volunteers can take part. These winter surveys use fixed transect routes, with all birds seen and heard being recorded, and the results are ideally submitted through BirdTrack. If you can identify common wintering species by sight and sound, and would like to take part in the SWBS, please contact Christine George for the full instructions and to be allocated a random square near to where you live (sussex.wbs@gmail.com).

For those interested in a summary of the results of the Sussex Winter Bird Survey (SWBS) over the nine winters Nov. 2011 – Feb. 2020, here is a PDF file containing the results.

The table is divided up into ‘winters’ with seven columns for each winter.

Column 1 = The list of all species encountered during the SWBS survey.
An orange fill represents the first time that species was encountered on the survey and a blue fill that the species was not encountered that particular ‘winter’ .

Column 2 (Tot Sq’s) = The total number of surveyed squares in which the species was encountered during that ‘winter’.

Column 3 (% of Sq’s) = The percentage of surveyed squares in which the species was encountered that ‘winter’ (as the number of surveyed squares is different each year, a percentage enables comparison from one ‘winter’ to another).

Column 4 (Mn Enc/Oc Sq) = Mean encounters per occupied square.
The mean number of encounters of the species per square in which the species was present that ‘winter’. This number is derived from the total number of encounters from both early and late visits divided by the number of squares in which that species was encountered. This number enables comparison from one ‘winter’ to another.

Column 5 (Mn Enc / Sur Sq) = Mean encounters per surveyed square.
The mean number of encounters of the species per square taking into consideration all of the squares surveyed in that ‘winter’. This number is derived from the total number of encounters from both early and late visits divided by the number of squares surveyed in that ‘winter’. This number enables comparison from one ‘winter’ to another.

Column 6 (Mean /Sq Vis) = Mean encounters per square visit.
As column 5 but divided by two to represent a visit rather than a ‘winter’ (as there are two visits per square per winter).

Column 7 (Total Enc) = The total encounters of the species in that ‘winter’.
This number is derived from the sum of the encounters from both the early survey (November or December) and the late survey (January or February).