Following the publication in 1984 of the first Breeding Bird Atlas of Catalonia and Andorra (Muntaner et al. 1984) and its 2004 update, the Catalan Breeding Bird Atlas 1999-2002 (Estrada et al. 2004), the preparation of a winter bird atlas to complement these previous publications was a logical step. Yet, despite good knowledge of the birds present during the breeding season, including their relative abundances, population estimates, ecological requirements and, in many cases, even trends in distributions and populations, little was known about many of the species that winter in Catalonia.



In fact, knowledge of Catalan wintering birds was very uneven: there was a considerable volume of information available regarding the species present, but very little detailed information on distributions, the ecological factors that determine birds’ presence and population dynamics. These shortcomings were even more serious given the importance of the Mediterranean basin as wintering quarters for a significant portion of birds that breed in central and northern Europe.

The publication of a winter atlas was a complex challenge. In winter birds are much less conspicuous than during the breeding season, when they are obvious as they mate and defend territories, or are actively feeding chicks and young birds. Winter is also a period of adverse weather, with cold, rain, snow and fog, and less daylight. Furthermore, some areas are of difficult access at this time of year, especially in snow-covered uplands. As well, birds tend to be much more dynamic in winter and sometimes sudden changes occur in their distributions and local abundances, a fact that makes systematic surveying even more difficult.



However, in light of our experience with the previous atlas, the collective conviction within the Catalan Ornithological Institute was that, despite the possible difficulties, we were prepared to confront this new challenge. The first question to resolve was what kind of atlas we wanted. Whereas it was clear that the breeding bird atlas should encompass all species for which there was evidence of breeding during a specific number of years, it seemed harder to define wintering birds: was it possible to separate wintering species from late or early migrants?; or breeding from non-breeding birds? given that many owls, Bearded Vultures and Common Crossbills are well into their breeding seasons in midwinter. Thus, we decided that, rather than an atlas of wintering birds (an ecological concept that is often hard to define), we would aim to create an atlas of birds found in winter (a purely temporal concept), regardless of their status. Thus, the data collection period was established as November 15-February 15 in the winters of 2006/07, 2007/08 and 2008/09, with a central core period of December 1-January 31 for the collection of quantitative data.

As was the case with the Catalan Breeding Bird Atlas 1999-2002, it seemed logical that this winter atlas should go beyond the mere distribution of birds at this time of year and, instead, attempt to produce and/or discern: 1) finegrained maps of abundance; 2) variations between winters and within the same winter; 3) information regarding altitude and habitat preferences; 4) population estimates; and 5) temporal trends. As well, it was also decided to include information from the significant number of winter bird ringing recoveries (Catalan Ringing Office) to try to ascertain the origin of the birds that spend the winter in Catalonia. Finally, another one of the objectives of the project was to investigate the distribution and abundance of the seabirds that in winter (unlike during the breeding season) may be completely pelagic in behaviour.



Unlike the Breeding Bird Atlas, right from the outset of the Winter Bird Atlas several established winter monitoring programmes such as the Catalan Common Bird Survey (SOCC) and the International Census of Wintering Waterbirds were already in operation. Thus, when designing a methodology and sampling strategy, existing projects were given priority in order to maximize the effort that collaborators were already undertaking. This fact and the aforementioned complexities inherent in the winter period obliged us to establish a somewhat different design from the Breeding Bird Atlas and to plan the sampling process so as to ensure that all areas and habitats would be homogeneously prospected each year.

In all, 885 people participated, far more than in the second Breeding Bird Atlas. Part of this increase is due to greater participation by collaborators who sampled specific 10 x 10 km squares for this new Atlas, but also to the fact that the volunteers who walk SOCC itineraries and the participants in the Census of Wintering Waterbirds were also taken into account. As mentioned before, the results from these projects were also included in the Atles and as such played an important part in its genesis.



Unlike the previous atlas, the lack of a prior winter atlas prevented us from an extensive assessment of species’ trends given that we could not analyse changes in distributions. However, as we felt that this issue was too important to ignore, a great effort was made to collate for the first time all old sampling series for wintering waterbirds in order to analyze trends occurring within these populations in recent decades. Similarly, for the commonest species data from the SOCC were also used in order to assess trends in recent years; even trends in seabird populations were analysed by comparing data from oceanographic campaigns.



The previous breeding bird atlases generated valuable tools for defining priorities in conservation strategies for biodiversity and land management, and the goal of this new winter atlas was to complete this information for the winter period. The Department of Environment and Housing of the Catalan Government and Caixa Catalunya’s Social Work programme once again were highly receptive to the idea of a ‘second phase’ and right from the beginning ensured that the winter Atlas would be published in its present format.

The Catalan Breeding Bird Atlas 1999-2002 was described by Professor Paul F. Donald as one of the top 10 bird atlases (Ibis 147: 616-630). We feel that, with this new publication, the Catalan Winter Bird Atlas, we have gone beyond our initial goals and that the efforts of so many collaborators have been truly worthwhile. The result is an atlas that complements perfectly the previous atlases. We hope it represents an important step forward in the knowledge of Catalan birdlife and rises even more the level of the science made by and for the citizenship.