Waterbird counts on large water bodies: comparing ground and aerial methods during different ice conditions

• Main Authors: Marchowski, Dominik, Jankowiak, Łukasz, Ławicki, Łukasz, Wysocki, Dariusz
• Format: Other/Unknown Material
• Language: unknown
• Published: PeerJ 2018
• Subjects: greater scaup; Northern Shoveler; Shoveler; Whooper Swan; smew
• Online Access: http://dx.doi.org/10.7287/peerj.preprints.26726; https://peerj.com/preprints/26726.pdf; https://peerj.com/preprints/26726.xml; https://peerj.com/preprints/26726.html

The paper compares the aerial and ground methods of counting birds in a coastal area during different ice conditions. Ice coverage of waters was the most important factor affecting the results of the two methods. When the water was ice-free, more birds were counted from the ground, whereas during ice conditions, higher numbers were obtained from the air. In ice-free conditions the group of waterbirds with the smallest difference between the two methods (< 6%) contained six species: Greater Scaup, Smew, Mute Swan, Goosander, Common Goldeneye and Tufted Duck; the group with a moderate difference (15%-45%) included another six species: Eurasian Coot, Whooper Swan, Mallard, Eurasian Wigeon, Great Crested Grebe and Common Pochard; while the group with a large difference (> 68%) included five species, all of the genus Anas: Gadwall, Eurasian Teal, Northern Shoveler, Northern Pintail and Garganey. In ice conditions, smaller numbers of most species were counted from the ground, except for Mallard, where the difference between two methods was small (7.5%). Under ice-free conditions, both methods can be used interchangeably for the most numerous birds occupying open water without any great impact on the results. When water areas are frozen over, air counts are preferable as the results are more accurate. The cost analysis shows that a survey carried out by volunteer observers (reimbursement of travel expenses only) from the land is 58% cheaper, but if the observers are paid, then the aerial survey is 40% more economical.