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Breeding Cetti's warbler survey FAQs

WHERE CAN I FIND HELP WITH IDENTIFYING CETTI'S WARBLERS?
In addition to consulting standard fieldguides volunteers may find the sound recordings at http://www.xeno-canto.org/species/Cettia-cetti useful. Cetti's warblers can be difficult to see as they tend to remain hidden in scrub and bushes so familiarity with the song and calls is essential for this survey.

WHEN DO CETTI'S WARBLERS BREED?
The breeding season for Cetti's warblers lasts from late April to mid-July; the young fledge by mid- to late August.

WHICH HABITATS ARE SUITABLE FOR BREEDING CETTI'S WARBLERS?
Cetti's warblers breed in areas of scattered scrub or bushes, either in reed-bed and marshy areas, or near open water, or beside rivers and wet ditches. In Sussex the preferred areas are along the river valleys, and also the coastal plain and levels areas (such as the Pevensey Levels) where there are extensive systems of wet ditches or rifes. For the purposes of the current survey, in any tetrad only areas of potentially suitable habitat need to be surveyed, and volunteers may find it useful to make an initial reconnaissance visit to each tetrad to identify these areas of suitable habitat.

HOW CAN I DISTINGUISH THE DIFFERENT HABITAT TYPES?
In order to distinguish between reed-bed, reed-swamp and fen/marsh habitats it is necessary to recognise the plants that are characteristic of these habitats. Reed-bed is dominated by Phragmites plants (see http://www.arkive.org/common-reed/phragmites-australis/) and these plants can also commonly be found along wet ditches. Reed-swamp typically consists of vegetation >0.6m tall and includes Typha plants (see http://www.arkive.org/bulrush/typha-latifolia/). Marsh areas typically do not have Phragmites or Typha plants but consist of lower vegetation that includes rushes and sedges. Unmanaged reed-beds naturally dry out and develop increasing amounts of scattered scrub and eventually woodland.

AM I EXPECTED TO SURVEY THE ENTIRE AREA OF MY TETRAD?
For the purposes of the current survey, in any tetrad only areas of potentially suitable habitat need to be searched (see comments above about preferred habitats). Volunteers may find it useful to make an initial reconnaissance visit to each tetrad to identify these areas of suitable habitat. If in any tetrad there is a very large area of suitable habitat, it is acceptable to conduct a single complete survey by making two or more visits; volunteers should indicate on the recording form the visits that make up a complete survey.

AM I EXPECTED TO SURVEY PRIVATE LAND?
Survey volunteers must only access private land with the permission of the landowner. A letter can be supplied to give to landowners if required. In practice, many areas of suitable habitat will be open access land or it will be possible to survey them from public rights of way. If it is not possible to access an area of potentially suitable habitat or to view the area from a public right of way, volunteers should indicate this unsurveyed area on the map of the tetrad.

HOW CAN SEPARATE CETTI'S WARBLER TERRITORIES BE DISTINGUISHED?
Each separate singing male indicates a separate territory, but differentiating two separate males from a single male that has moved can be difficult. For this reason it is especially important to record on the maps whether or not singing birds are heard simultaneously or whether they are observed moving between locations. Male Cetti's warblers patrol their territory boundaries, and can move quite long distances; linear territories (e.g. along river banks or ditches) can be up to 450 m long. In addition, some male territories may overlap, particularly in areas with a high density of Cetti's warblers, so care must be taken not to double-count individual males. Cetti's warblers are polygynous with up to three females nesting within a single territory, so observations indicating nest sites (birds carrying food etc) should not be assumed to indicate separate territories. In many cases there will be uncertainty about whether registrations relate to separate territories or not. For this reason a range of possible numbers of territories within the tetrad rather than an exact number can be suggested based on the evidence available.

WHAT SHOULD I DO IF THERE IS NOT ENOUGH SPACE ON MY MAP?
Printable maps of tetrads at a 1:50,000 scale are provided. If in any area of a tetrad numerous registrations of Cetti's warblers mean that it becomes difficult to mark these registrations clearly on the map, volunteers should make photocopies of the area at a 1:25,000 scale and use these or use a separate tetrad map copy for each registration or group of registrations (it is essential that the maps show how the registrations relate to each other, i.e. whether or not two singing birds were heard simultaneously). In some cases a large-scale sketch map of the area may be helpful.

SHOULD I RECORD OTHER SPECIES SEEN DURING MY SURVEYS?
It will be very valuable if volunteers can record other species seen or heard during surveys, as long as this does not reduce the accuracy and completeness of the recording of the required information about Cetti's warblers. Other species can most easily be recorded in BirdTrack www.bto.org/volunteer-surveys/birdtrack. These records are most useful in the form of complete lists (recording all species seen or heard) and volunteers should ensure that Cetti's warblers are included in complete lists.

WHAT SHOULD I DO IF I SEE OR HEAR CETTI'S WARBLERS ON A TETRAD BOUNDARY OR IN AN ADJACENT TETRAD?
There will be some Cetti's warbler territories that span two or more tetrads. If Cetti's warblers are observed or heard on the edge of a tetrad the volunteer should mark on the map the exact locations where they observe or hear the birds and use the margin of the map, i.e. the map area outside the actual tetrad, to mark the registrations in the adjacent tetrad. If Cetti's warblers in the same territory are also heard and recorded (and they may not be) by the volunteer surveying the adjacent tetrad this will become apparent at the analysis stage.

Similarly, if birds are observed or heard in an adjacent tetrad but not in the tetrad being surveyed, these should be plotted on the margin of the map and if possible notes should be made as usual about activity and habitat. The volunteer surveying the adjacent tetrad may miss those birds and it is also possible that the adjacent tetrad has not been allocated to be surveyed at all.

DO I NEED TO CONFIRM BREEDING FOR ALL PAIRS IN THE TETRAD?
The aim of the survey is primarily to find out the numbers of singing males in different tetrads and confirming breeding is absolutely not necessary. Cetti's warblers are polygynous with up to three females nesting within a single territory, so whilst it is important to note evidence of breeding if it is observed, such as birds carrying food or adults with dependent young, these observations should not be assumed to indicate separate territories. Furthermore, the Schedule 1 status of Cetti's warblers means that it is an offence to intentionally or recklessly disturb the birds at or near active nests, so nests should NOT be searched for and nesting birds should be observed from a distance.

 
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