"Timed count" fieldwork forms the basis of the BBS, providing three essential elements of data:

To ensure completeness of data, each of the 671 1Km squares encompassing landmass of the Isle of Man is being surveyed by employed staff, ensuring a high level of observer consistency. Fieldwork is carried out during the period 1st April - 31st July each year, with approximately 20% of the total number of 1Km squares being surveyed in each year.

Each 1Km square is surveyed for a total of four hours, once for a period of two hours during the `early' part of the season (1st April - 31st May) and again for a further two hours during the `late' part (1st June - 31st July). For coastal squares incorporating areas of sea, the allocated survey time is linked proportionally to the area of landmass present. Whilst undertaking these visits, the fieldworker maps the survey route walked, whilst attempting to visit all representative habitats within the survey square. The second visit retraces the route marked out during the first "timed" count.

Although some modifications have been necessary, the methods follow in principal the recommendations of the 88-91 Atlas (UK), ensuring that those species more detectable early in the season are recorded, as well as ensuring coverage of the late arriving migrant species.

Whilst undertaking the survey, the fieldworker records all species seen and or heard. These observations are recorded on a "count" sheet and a 1:4000 OS map providing evidence of the species being present in a given 1Km square.

For each observation, the fieldworker assigns an activity code that describes what the bird/s activity was. Depending upon the observed activity, the breeding status of the species is determined from the following list.

This latter category has been developed to allow more detailed recording of individual bird activity, given the very accurate mapping that is being employed. This "holding" category allows for the recording of those species using a 1Km square but thought not to be breeding, as well as those which were observed (flying over or through) but thought not to be using the 1Km square. Such details, particularly for summering non-breeding birds is valuable, from a conservation point of view, as it is likely that these birds may represent the future breeding stock.

Additionally for certain migrant species, a date was chosen up to which all records of individual/s in suitable habitat are treated as "other". These dates, shown below, were initially calculated by adding three weeks to the average arrival date; a period thought to be sufficient to allow most birds to arrive onto their breeding territories. The validity of choosing these dates is reviewed annually by examination of observations for each species. It is possible that, over the life of the project, one or more of these dates might change.

In the course of each "timed" count survey, all individuals are counted and recorded onto the "count" form. These totals provide the necessary data by which relative abundance can be calculated.

Point counts are now recognised as providing the best method by which absolute abundance data can be collected and it is proposed that a sample of 71 randomly selected 1Km squares are to be surveyed. Within each count square a series of four counts (clusters), will be conducted; each being on a diagonal from the centre point, sufficient to give a distance of 250 metres from any of the other points surveyed.

Two series of counts will be conducted at each cluster location, once during the six-week period between mid-April to May and again during June to mid-July, ensuring the optimum opportunity for species detection. Each `count' will be conducted using the "moment-in-time or snapshot" sampling technique as described in Distance Sampling by Buckland et al. (1993). The fieldworker will record all individual birds, seen or heard, onto a count sheet and 1:4000 OS map. At the count moment, each observation still present is recorded and an accurate distance from observer is recorded using a pair of Yardage Pro 400 laser binoculars. Point counts are conducted between dawn and 1100 hrs (BST), when birds are at their most active.

Whilst the programme of 1Km "timed count" visits is very comprehensive, it is recognised that this method of surveying does not take into account some of the more "difficult to survey" species and is for those species likely to produce data which is both misrepresentative and misleading. To overcome this problem certain species specific or group specific related projects have been identified which will enable, the distributions of these less common species to be mapped more accurately. A list of species is given below, which indicates the year or years for which species specific monitoring is proposed.

The species listed have been included for one or more of the following reasons:

Additional information collected by members of the public and by mba staff, whilst not undertaking formal surveys, provides data that will inform species distribution ensuring the species list for each 1Km square is as complete as possible. This is particularly important for some of the rarer and nocturnal species. Voluntary fieldworkers are playing a vital role in this aspect of the Atlas work.

In order to attain a level of coverage, which is both achievable and will provide accurate and meaningful results, the land mass of the Island is being surveyed by tetrads (2x2Km squares of the National Grid). "Timed count" fieldwork, involving a single four-hour visit to each tetrad is carried out by employed fieldworkers. For coastal squares incorporating sea, the allocated survey time is linked proportionally to the area of landmass present. Whilst undertaking these visits, the fieldworker maps the survey route walked, attempting to visit all representative habitats within the tetrad. This maintains a high level of observer consistency, similar to that attained by the BBS. This data provides the base from which the relative abundance and distribution of the Island's wintering bird populations will be estimated.

Fieldwork is being carried out during the three winter's 1998/9, 1999/2000, and 2000/1 and encompasses the period mid-November until the end of February. Actual dates for the survey are 15th November 1998 to 28th February 1999, 16th November 1999 to 29th February 2000 and 15th November 2000 to 28th February 2001 inclusive, giving a total of 345 fieldwork days during the three winters.

In order to measure relative abundance, fieldworkers will be required to count all birds seen or heard within each tetrad and will map observations at a six-figure grid reference level, allowing presentation of species distribution at 1Km square level. All observations are recorded and assigned an activity code, which enables distinction between those species using the tetrad and those just seen flying over or passing through. This also allows obvious passage migrants to be identified. Where possible, survey counts, are carried out during the period 8.30 am to 2.30 pm GMT.

Additional visits to further record species presence is being undertaken within each tetrad. These visits do not have any time restrictions although the observer should try to visit all 1Km squares and as many representative habitat types as possible. Additional visits undertaken in 1998/9 encompassed those tetrads selected for "timed count" survey in 1999/2000 and additional visits in 1999/2000 will incorporate 2000/1 "timed count" tetrads and 2000/1 additional visits will re-visit the 1998/9 "timed count" tetrads.

Line transects provide the best method of obtaining absolute abundance levels of winter bird populations. Using pioneering methods devised with Professor Steve Buckland of St. Andrews University, mba will be the first atlas to collect absolute abundance information.

Winter Atlas line transect data will be gathered from a randomly selected sample of 20 tetrads, with a sample of four, 250 metre, line transects being undertaken in each tetrad. The key information required to ensure that reliable absolute abundance data can be calculated is the perpendicular distance of the observation from the transect line.

The fieldworker is required to walk a route that is due north of the centre of each transect point, usually the centre of each 1Km square in the tetrad. If it is not possible to walk this route, due to terrain or for some other reason, then a route that is due east, west or south of the centre point should be chosen. Having chosen the route to walk, the fieldworker should mark it on a map and make a mental note of its length and direction in the field, using a compass and visual markers as reference points to ensure maintenance of direction and length of survey line.

All birds seen within the 250m transect line should be recorded, including those seen within the transect boundary before the fieldworker arrives at the starting point of the transect line. It is important that birds observed beyond the end of the line are not counted.

Additional information collected by members of the public and by mba staff, whilst not undertaking formal surveys, provide data that will inform species distribution. Additional data will be provided through initiatives such as Garden BirdWatch 2000, which is designed to allow participation of the general public throughout the Island in recording bird species visiting gardens during the period 21st November 1999 - 19th February 2000.

To enable the accurate assessment of abundance it is important that systematic biases do not occur within the fieldwork methods. In using employed fieldworkers, it is possible to avoid the three main problems identified by the 88-91 Atlas (UK):

The need for a scale against which to measure abundance is obvious and within the 88-91 Atlas (UK) a number of techniques were employed depending on the species in question. It is intended that, as appropriate, the following methods will be used to identify population estimates for the Isle of Man.

This information is obtained automatically by comparing the number of individuals, of a given species, recorded between 1Km squares for BBS and between tetrads for the WA.

Information derived solely from point and line transect counts will be used to produce absolute abundance levels for a number of common passerines.

Funding is currently being sought to develop a spatial distance sampling model for both the breeding bird point transect data and the winter atlas line transect data, using land cover data and the 1Km square counts as covariates. For the more common species, this will allow estimation of:

For a few species, a reasonably accurate estimate of the population can be derived from the "timed counts" undertaken as part of the BBS. For many species, it will be impossible to ensure the recording of every individual; however, this method will provide at least a minimum population size. The degree to which the population is underestimated will depend on how visible the species is and the types of habitat that it occupies. The Specific Species Project work will provide invaluable information that will, at least in some part, alleviate this problem for some species.

This index was the primary method used in producing population estimates for the 88-91 Atlas (UK). Population estimates were derived by multiplying mean woodland, farmland and other habitat CBC densities by the area of each habitat type in Britain. It is unlikely, due to a very small sample range, that such methods could be employed for the Isle of Man. However, additional fieldwork would not be required and the methods will remain under review.

The BBS element of this project is the first to survey an area the size of the Island by 1Km square monitoring. This method has been chosen, due to the Islands highly diverse topography and habitats, in order to provide very detailed information, of lasting value to the Island. The survey methods chosen will allow comparison to Atlas work carried out in the UK, particularly that of 1988 - 1991. The WA will provide valuable data on the importance of the Island as a wintering location for both migratory and resident species.

This is providing the opportunity to accurately measure existing levels and forms a base from which to measure changes in populations at a later date. As we move into the 21st. Century, this project is already collecting the most comprehensive set of data on Manx birds ever.