What do data from birdwatchers notepads tell us? The case of the Bearded Tit (Panurus biarmicus) occurrence in western Poland
Birdwatchers gather significant amount of casual observations which are often used in scientific research. However, accuracy of this data is seldom controlled. The aim of this study was to detect if casual observations reflect real situation in the case of Bearded Tit occurrence. Two sources of data were compared: different birdwatchers casual observations (CO) and results of regular studies (RS) carried out in the same region by the author. In the case of RS, study areas were selected randomly and playback method was used to maximise efficiency of species searching. It has been revealed that birdwatchers explore mainly large lakes and big river valleys. Small marsh patches and streams, where significant part of Bearded Tit sites is located, are usually omitted. According to CO data, the peak of non-breeding birds, which normally occurs in the first half of October, took place a month later. This shift resulted from higher birdwatchers activity connected with holidays in the beginning of November and dynamics of rare waterbirds in the region. Flocks of wintering Bearded Tits found during RS were significantly smaller than in CO. Possible causes of observer biases are presented and discussed.
If the inline PDF is not rendering correctly, you can download the PDF file here.
Baillie S., Balmer D., Downie I., Wright K. 2004. Migration watch - an Internet survey to monitor spring migration in Britain and Ireland. Proc. 16th Int. Conf. EBCC, Kayseri, Turkey: p. 26.
Bednorz J., Kupczyk M., Kuźniak S., Winiecki A. 2000. [Birds of Wielkopolska. Faunistic monography.] Bogucki Wyd. Nauk., Poznań. (In Polish).
Chamberlain D. E., Cannon A. R., Toms M. P. 2004. Associations of garden birds with gradients in garden habitat and local habitat.Ecography 27: 589-600.
Crick H. Q. P., Baillie S. R., Leech D. I. 2003. The UK Nest Record Scheme: its value for science and conservation.Bird Study 50: 254-270.
Dyrcz A., Grabiński W., Stawarczyk T., Witkowski J. 1991. [Birds of Śląsk. Faunistic monography.] Wrocław. (In Polish).
Fraser P. 1997. How many rarities are we missing? Weekend bias and length of stay revisited.Brit. Birds 90: 94-101.
Kuźniak S. 1983. Passage and wintering of waterfowl in the Krzywińskie Lakeland (western Poland).Acta orn. 19: 237-250.
Kuźniak S., Lewartowski Z., Winiecki A. 1991. Avifauna of the lakes in the Wielkopolska region in autumn.Not. Orn. 31: 55-76.
Sokal R. R., Rohlf F. J. 1995. Biometry. W. H. Freeman and Company, New York.
Surmacki A. 2003. Use of playback in estimating numbers of Bearded Tit Panurus biarmicus outside the breeding season.Ornis Hungarica 12-13: 303-305.
Surmacki A., Stępniewski J. 2003. A survey of the Bearded Tit Panurus biarmicus during the non-breeding season in a landscape of Western Poland.Acta orn. 38: 53-58.
Wawrzyniak H., Sohns G. 1986. Die Bartmeise. Die Neue Brehm-Bücherei. A. Ziemsen Verlag, Wittenberg Lutherstadt.
Wesołowski T., Czuchra M. 2003. Polish Nest Record Scheme - 25 years of activity.Not. Orn. 44: 149-157.
Vorisek P., Gregory R. D., Van Strien A. J., Mayling A. G. 2004. Population trends of 48 common terrestrial bird species in Europe: first outputs of the Pan-European Common Bird Moinitoring Scheme. Proc. 16th Int. Conf. EBCC, Kayseri, Turkey: p. 28.