Bringing Reedbeds to Life Amphibian Survey of two key reedbed sites in England in 2010

Quality Control

These data have been gathered by trained field-workers and the data are of a high quality. These data have been mapped and checked for sensitivities and typographical/geographical errors.

Method steps

1. Common frog survey method: Visual searches for frogspawn were carried out, searching as much of the reserve as possible. When found, the spawn mat size was measured, number of clumps were counted and habitat around the spawn was surveyed.
   
   Newt survey method: Bottle trap surveys were conducted between 15th March and 4th June. Six rounds of trapping were carried out at each site at fortnightly intervals. Although we can never be certain of newt absence, six repeats was deemed enough to give a confident estimate of where newts were present and absent (Sewell, D. pers. comm.) Traps were placed on 40 randomly allocated transects around each reserve, spaced to be as independent as possible. Each transect had ten newt traps, spaced 2 m apart. Number of newts and small fish caught in traps were recorded. The transect habitat was surveyed, including measures of water quality, vegetation and habitat structure. For analysis, comparisons of habitat variables were made between transects with and without newts. In addition, habitat variables were tested to see which related most strongly to the maximum number of newts caught on each transect over the six rounds of trapping.
   
   Marsh Frog survey method: Any sightings or calls throughout the 2010 survey season were marked on a map to estimate distribution.
   
   The aim was to cover the whole reserve via a pre-plotted transect route. Known ponds were marked on the map to ensure these were surveyed. There were 25 survey points at Stodmarsh and 27 at Ham Wall, sampled 3 times over the week. The transect route was varied each day to randomise the time of day each survey point was sampled. Every 500 m along the transect, calls were listened for over 2 minutes, forwards 250m and backwards 250m along the transect. Records were made of whether calls were in the front 250m or the behind 250m, on the near side bank or opposite bank across the ditch/water. Then a 15 second sound clip of marsh frogs calling was played using the MP3 player and speaker. Again 2 minutes of listening in the areas specified above was carried out. In addition, walking along a 10m stretch of bank flushed frogs into the water. This was either seen or a distinctive plop sound was heard and the number of individuals counted. Marsh frogs seen or heard between survey points were added to the distribution map.
   
   Surveys were designed by Donna Harris (former RSPB project officer) with expert advice from various herpetologists. Surveys were carried out by RSPB staff and RSPB volunteers.
   
   In order to verify records and validate the dataset, the data have been mapped and thoroughly checked. Geographical checks have included comparing the distribution with that shown in the published paper and ensuring that records with the same area name are located close to each other.

It is recognised that this data is only from the breeding season in one year. Records of frogs will be biased towards areas that were more accessible on the reserves, although extensive effort was taken to cover as much of the reserve as possible. Newt records do not suffer from this bias since they are from traps placed along transects.

Bringing Reedbeds to Life Technical report with further method descriptions will be available after 31st March 2011 at www.rspb.org.uk/ourwork/projects/details.aspx?id=tcm:9-210865