Changes In Number Of Birds Research Articles

Do moorland breeding waders avoid plantation edges?

Nine moorland sites adjacent to coniferous plantations were surveyed for breeding birds in Sutherland and Co. Durham. Fewer Golden Plover and Dunlin were seen close to plantations than further away. The total number of wader sightings (i.e. Golden Plover, Dunlin, Redshank, Curlew, Lapwing, Snipe, Greenshank and Common Sandpiper combined) followed the same pattern. For Golden Plover and all waders combined, the effect extended up to 400 m from the forestry edge. For Dunlin the effect extended beyond 400 m from the forest edge. On a subset of 5 sites, there was no evidence for vegetation changes which might account for these patterns. However, this failure to detect changes in the vegetation may be due to the methods used. Comparisons are made with earlier studies, and possible mechanisms are discussed. Changes in bird numbers with distance from the forest edge could be due to the way sites are selected for forestry, or due to 'edge effects'. A study suggesting that map-derived variables, which could have been influenced by afforestation, change with distance from the forest edge is consistent with the first of these hypotheses. Studies suggesting changes in vegetation, in association with afforestation, are consistent with the second. Further research is necessary to investigate the relative importance of these 2 possible mechanisms. This research should be carried out before further forestry developments near important areas for nature conservation.

Perspectives in using shorebird counts for assessing long-term changes in wader numbers in the Wadden Sea

Over the past 20 years, a tradition has developed in western Europe of carrying out shorebird surveys in estuaries. These counts are mostly conducted by amateur ornithologists, usually well acquainted with the area in which they are active. The results of these surveys are well reproducible for at least the abundant species, and information is available on the size of the errors which occur. In several parts of Europe, shorebird surveys have been carried out long enough to allow trend analysis of population size. Four examples from Great Britain demonstrate that monitoring schemes may also be used for management purposes, especially if combined with specific research projects. Long-term shorebird surveys can be used not only for simple analysis of trends in bird numbers, but also to provide a deeper understanding of the functioning of the ecosystem. They may also act as a tool to document the effects of management activities in the area concerned. Shorebird surveys in the Wadden Sea have not only revealed the extremely large importance of the area, especially for waders, but also show that different areas are exploited in different ways. They have also provided data on changes in bird numbers throughout the year. Apart from the counts carried out in January, the frequency of counts in most areas in the Wadden Sea has been too low to allow the results to be used for monitoring purposes. In an area as large as the Wadden Sea, some sites, often supporting large numbers of birds, may not always be covered during simultaneous surveys. This may seriously affect the completeness of the count. The best way to overcome this problem is to calculate index values, using only those sites which have been surveyed in successive years. Two monitoring schemes are proposed which may be effective in providing relevant information for management purposes.

The guild concept applied to management of bird populations

Alternative ways to apply the guild concept to wildlife management are evaluated here. I reject the idea that indicator species can be selected for each bird guild to reduce costs of environmental assessment and monitoring. Promise is seen, however, in the option of using whole guilds to indicate the capability of habitat zones to support populations of wildlife species. It may be adequate for most management purposes to delineate guilds only for species that use an environment for breeding, because transients and winter residents probably use the same zones of the habitat in the same ways. Potential guilds are identified by cells of a two-dimensional matrix, the axes identifying primary feeding and nesting zones. Some questions may be answered with guilds as delineated by all cells in the matrix. Alternatively, larger guilds can be formed by grouping all species in each column or row of the matrix to identify, for example, all species that depend on tree canopies for foraging, or tree boles for nesting. One can also consider separately the resident breeders, migrant breeders, and winter residents to obtain insights into whether observed changes in numbers of birds in a guild are a result of conditions locally or elsewhere. I conclude that the guild concept probably has a place in wildlife management, but much testing must be done before it is widely applied.

Some Effects of Neutron-Gamma Radiation on Late Summer Bird Populations

IN 1960 the late summer bird populations of a small valley 50 miles north of Atlanta, Georgia, were exposed to high level neutron-gamma radiation which was released from a 10 megawatt, air-shielded nuclear reactor at Air Force Plant 67. The reactor operated for five days in each of three consecutive weeks and was shut down on weekends. The purpose of this study is to compare the changes in numbers of birds living in the radiated valley with those in a similar non-radiated area.

Daily and Seasonal Crowing Frequency of Ring-Necked Pheasants

Crow counts (number of calls) of cock pheasants (Phasianus colchicus) obtained during spring are used widely in the United States as indices for detecting relative changes in numbers of birds between years and different areas. The reliability and comparative value of these counts are affected by many factors. According to Nomsen (1953) and Klongland and Kozicky (1953), counts should be made at the same time of day in relation to sunrise in order to give comparable data. Kimball (1949) states that on rainy days crowing is less than on clear days. McClure (1944), while inducing crowing by detonations, noticed that optimal temperature range for crowing appeared to be between freezing and 500 F.