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Study area
Unlike the first atlas (carried out between 1975 and 1983), which included Andorra and areas within Aragon and France in cross-border squares (Muntaner et al. 1984), in the present atlas the study area was strictly limited to the administrative territory of Catalonia. In those border squares in which a part of the square lay outside Catalonia, the surveyed area was restricted to the Catalan portion of the square.
Sampling methods
Each observer responsible for a 10x10 UTM square had to survey the whole square. The aim of the sampling methodology was to detect either by sight or by sound the maximum amount of evidence of breeding for all the species present. To do this, the observers were asked to try to survey all habitats, even minority ones, present within their square in order to avoid overlooking any species.
The execution of timed censuses as a means of producing abundance maps is one of the most significant features of the present atlas. Besides the generic sampling conducted for each UTM 10x10 square, a set of sample 1x1 km squares was established inside the former units: this approach is similar to that used, for example, in the British and Swiss ornithological atlases (Gibbons et al. 1993, Schmid et al. 1998). These 1x1 km units were established by dividing each of the UTM 10x10 squares into 100 UTM 1x1 squares: initially the aim was to survey a minimum of 10 UTM 1x1 squares per UTM 10x10 square. Only in the case of those squares that were insufficiently covered and therefore had to be surveyed semi-professionally was the minimum lowered to five 1x1 squares. Two 1-hour surveys were conducted for each one of the selected UTM 1x1 squares during which every square was entirely surveyed and every species recorded. The number of individuals was not noted.
Study period
The field work was conducted in the period 1999-2002. Sampling was exclusively carried out by volunteers in a totally altruistic fashion during the first three years. During the last year of sampling, a team of six ornithologists working semi-professionally covered the gaps left by the volunteers.
As a general rule, the gathering of evidence of breeding was restricted to the period March-July inclusive. If possible, surveys had to be conducted between sunrise and 11 am, and between 6 pm and sunset. Timetables and dates were approximate and could be adapted to local conditions, provided that surveys were conducted coinciding with peaks of bird activity. As well, for confirmed evidence of breeding data obtained in dates previous or posterior to the prescribed surveying period were accepted, especially for those species with very long reproductive seasons. The surveying period for nocturnal raptors was brought forward to February so that the territorial songs of species that principally call in the winter could be detected (for example, Eagle Owl, Long-eared Owl and Tawny Owl). In the UTM 1x1 squares the first survey was conducted in March/April to detect resident species and the second in May/June to detect summer visitors.
Taxonomy
The taxonomy and nomenclature follow a new version of the list used by the Catalan Avifauna Committee (Comitè avifaunístic de Catalunya, CAC 2003) incorporating the recommendations of the Association of European Records and Rarities Committees (AERC TAC 2003). For the exotic species that do not appear in these recommendations, the nomenclature and sequence proposed by Clements (2000) has been adopted.
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Projecte ATLES
ICO-Oficina Tècnica
Girona 168, entresol 5a
08037 Barcelona
Tel: 93 458 78 93
atles@ornitologia.org
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Catalan Winter Bird Atlas 2006-2009
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