Ib Krag Petersen

Waterbird Populations and Pressures in the Baltic Sea

This report outlines the results of the internationally coordinated census of wintering waterbirds in the Baltic Sea 2007-2009 undertaken under the SOWBAS project (Status of wintering Waterbird pop ...

Using object-based analysis of image data to count birds: mapping of Lesser Flamingos at Kamfers Dam, Northern Cape, South Africa

Knowing instantaneous locations and numbers of individuals in animal populations is a major requirement for wildlife and conservation ecology. Recent advances in very high spatial resolution digital-imaging systems and in object-based image-analysis methods offer great potential for developing remote sensing in new application arenas, including direct mapping and counting of birds, mammals and other larger organisms. We present the successful application of an automated object-based image-mapping strategy that has been applied to total mapping, using aerial image data, of Phoeniconaias minor (Lesser Flamingo) individuals at Kamfers Dam, a large perennial lake in central South Africa. The object-based method used quadtree image segmentation and sequential object-brightness thresholding to identify individual birds with high accuracy (>99% compared to human visual interpretation). Accuracy-assessment results are presented, with discussion of the error factors related to the object-based method and the reference data. An under-estimation by the object-based method of less than 0.5% is indicated. The automated procedure mapped 81 664 Lesser Flamingos at this one site, which is 30% above the most recent estimated size of the entire southern Africa Lesser Flamingo population, indicating a need for further work to reassess this populations size.

Response of breeding waders to agri-environmental schemes may be obscured by effects of existing hydrology and farming history

The initiation of agri-environmental schemes (AES) to improve habitats for breeding waders may not show expected benefits in all situations. We show this, using results from a study of breeding waders on 469 grassland fields in the Danish Wadden Sea area. Numbers of breeding waders were not restored to levels of the recent past, even though Lapwings Vanellus vanellus, Black-tailed Godwits Limosa limosa and Redshanks Tringa totanus were drawn to wet permanent grasslands with AES. We had expected that more waders would be attracted by improved surface water retention during the breeding period due to the AES. However, AES were not introduced to all fields, and this measure did not dramatically change the water regime in part of the breeding fields. Furthermore, dry grasslands and fields that had been cultivated or drained before did not attract more waders, despite the introduction of the AES. The results suggest that the interplay between surface water retention and former farming history are important determinants of the habitat choice for breeding waders. The study emphasises the need for pre-defined success criteria, thorough analysis of the nature of the habitat and consideration of population processes before initiation of an AES, so that realistic management goals are defined and expected benefits can be achieved.

Trends and drivers of change in diving ducks

This report addresses changes in population size in five species of diving ducks breeding and wintering in the Baltic Sea. Declines in breeding Greater Scaup, Eider and Velvet Scoters on the Baltic ...