Long-term Decline In Number Research Articles

Long-term monitoring of the European roller (Coracias garrulus) in Ukraine: is climate behind the changes?

The European range of the roller was formerly more extensive, but since the 1980s there has been a long-term decline in numbers and in range, particularly towards the north, including much of north-western Ukraine. Our specific goals were to reconstruct the environmentally suitable range of the species in Ukraine before the 1980s, gain better knowledge on its requirements, compare the past and current suitable areas, infer the regional and environmental variables that best explain its occurrence, and quantify the overall range change in the country. For these purposes we created a database consisting of 584 findings made in Ukraine, based on a lengthy record of occurrences extending back to 1851: 203 for the period prior to 1980, 91 for records made between 1985 and 2009, and 290 records made between 2010 and 2020. We employed a species distribution modelling (SDM) approach to hindcast changes in the suitable range of the roller during historical times across Ukraine and to derive spatially explicit predictions of environmental suitability for the species under current climate and a set of factors that were hypothesised to be of importance to roller presence and securing a sufficient food base. SDMs were created for three time intervals (before 1980, 1985–2009, 2010–2020) using corresponding climate data. SDMs show a decline of suitable for rollers areas in the country from around 86 to 44%. Several factors, including land cover and land use, human population density etc. that could have contributed to the decline of the species in Ukraine, were considered. For example, the loss of area of ‘short vegetation’ appears detrimental, although recent gains in this respect have favoured the bird in the Chornobyl Exclusion Zone and around, where Landsat images show the change from a previously vibrant agricultural and forestry economy, when crops have been replaced by grasslands. Threats posed to the roller by habitat and land use change are also likely to be compounded by the effects of global climate change. In summary, we suggest climate change, in particular velocity, have been responsible for shaping the contemporary home range of the European roller in Ukraine and perhaps beyond.

How Different Landscape Elements Limit the Breeding Habitat of Meadow Bird Species

Meadow bird species in the Netherlands have shown a long-term decline in numbers. This has been generally attributed to agricultural intensification, but in addition an increase of disturbing elements may have played a role in the decline. In this review we compiled data from literature to explore to what extent breeding by meadow birds (Eurasian Oystercatcher Haematopus ostralegus, Northern Lapwing Vanellus vanellus, Black-tailed Godwit Limosa limosa) is limited by disturbing landscape elements. We considered elements that can be considered ‘view-obstructing’ (like trees or houses), and those that can be considered ‘flat’ (canal, road or railway). Our review shows that breeding birds keep a distance to both types of landscape elements, with distances ranging over 1 km for highways and village edges. Roads with high traffic intensity caused the largest disturbance. Eurasian Oystercatcher was most tolerant to the presence of landscape elements, and Black-tailed Godwit least tolerant.

Nest habitat selection of White-winged Scoters on Yukon Flats, Alaska

Breeding bird surveys indicate a long-term decline in numbers of scoters (Melanitta spp.) breeding in North America. Little is known about the breeding habitat and reproductive life history of White-winged Scoters (M. fusca) in their primary breeding areas in the boreal forest of Alaska and northern Canada. We characterized selection of nest habitats and attributes within those habitats by measuring variables at nests and random sites on the Yukon Flats National Wildlife Refuge, Alaska. White-winged Scoters avoided nesting in meadows, but nested in scrub or forested habitat types in proportion to their availability (χ25 = 9.7, P = 0.08). Nests of radio-marked females were farther from water and edge ( 210 ± 43 and 10 ± 4 m, respectively), and in slightly thicker cover ( 6 ± 4%) than nests located without aid of radio transmitters. Females selected sites with more variable and abundant overhead and lateral cover, and sites closer to edge and water than random sites. The results imply nearly random use of scrub and forested habitat types within the study area, but selective use of attributes within those habitat types. This generalist approach to nest site selection at a larger scale may be an adaptive response to reduce detection by nest predators. Nests located without use of radio-marked females may not be representative of the population of nests at a study site. White-winged Scoters often selected nest sites with dense cover far from water, which may increase nest survival. However, concealed sites are difficult for heavy-bodied birds to escape and females may be trading productivity against their own mortality.

Identification of Landscape Elements Related to Local Declines of a Boreal Grey-sided Vole Population

Several studies indicate a long-term decline in numbers of different species of voles in northern Fennoscandia. In boreal Sweden, the long-term decline is most pronounced in the grey-sided vole (Cl ...

LONG-TERM DECLINE OF VOLE POPULATIONS IN NORTHERN SWEDEN: A TEST OF THE DESTRUCTIVE SAMPLING HYPOTHESIS

Time series data on cyclic vole populations in 1971‐1999 in northern Sweden show a longterm decline in numbers from the early 1970s to the late 1990s. We tested the destructive sampling hypothesis predicting that previously unsampled (new) plots in remote areas would yield higher density indices than the density level of permanent plots in the early 1970s. In autumn 1999 we sampled both permanent (treatment) plots and new (control) plots. Density was not higher on new than on permanent sampling plots for any of the predominant vole species, Clethrionomys glareolus, C. rufocanus, and Microtus agrestis. It appears unlikely that destructive sampling has caused the observed decline in vole numbers.

Population trends of Swallows Hirundo rustica breeding in Britain

Capsule There are regional and habitat differences, but no long-term decline in numbers. Aims To review the evidence for declining Swallow populations in Britain, based on the British Trust for Ornithology's long-running Common Birds Census (CBC) and suggest possible causes. Methods Trends were fitted to CBC data for 1964–98 using a generalized linear modelling framework and analysed with regard to specific regions and habitats. Current habitat use, particularly of different farming types, was characterized using data from the Breeding Bird Survey. Correlations between Swallow population size and loss of nest-sites and rainfall in the non-breeding grounds were examined. Results Although Swallow numbers show large annual fluctuations, there is no evidence for a long-term decline on CBC plots. Numbers seem to have declined on farms in eastern England and in non-farmland habitats, but were not correlated with changes in cattle numbers or with an index of regional changes in nest-site availability. The number of Swallows breeding each year in Britain was not correlated with rainfall on their wintering grounds but was correlated with rainfall in the western Sahel on spring migration. Conclusion Changes in farming practice do not appear to have had a long-term effect on Swallow numbers. Although Swallows show high breeding site fidelity, changes in breeding location may mean local declines are not reflected in regional or national population trends.

Visitor cycles: Outlook for tourism in Lancaster County

Various writers have suggested that tourist areas undergo a cycle of evolution ending eventually in decline. This article suggests a five-stage evolutionary sequence appropriate to Lancaster County, Pennsylvania, one of the leading tourist destinations in the United States. Elements of the County's physical and psychological carrying capacity are considered in ascertaining whether Lancaster County will undergo a significant permanent decline in tourist activity. The magnitude of possible future decline is influenced by relative location, diversity of the tourist base, and effectiveness of planning. Diversity and relative location clearly favor Lancaster County in comparison with competing tourist areas and will help to prevent significant long-term decline in number of visitors.