Habitat use by Palaearctic migrant passerine birds in West Africa

Data on passerine migrants in West Africa published since the works of Moreau j 1972) and Curry-Lindhal (1981) are reviewed and new information on wintering ranges are summarized. An important feature of West Africa as a wintering zone is the presence of the two great river basins of the Senegal and the Niger, which are responsible for the Sahel being far richer than would be expected at this latitude. This 'paradoxical' or 'green' Sahel is under the threat of agricultural developments and of increasing desertification. Conversely, Palaearctic migrants can take advantage of the new-savanna/forest mosaics and agricultural developments which have replaced the rain forest.     

Habitat use by a Neotropical desert marsupial (Thylamys pallidior): A multi-scale approach

In South America, most didelphid marsupials are associated with tropical and moist forests; however, a few species are adapted to more extreme environments such as desert systems. The desert mouse opossum, Thylamys pallidior, is a small marsupial which inhabits the arid regions of South America and has the broadest distribution of the genus. The objective of this research was to assess the habitat use and selection by the desert marsupial T. pallidior considering different scales and habitat levels of analysis, as well as seasonality. We considered two habitat levels (macro and microhabitat) and the microhabitat was analyzed at two spatial scales (1 ha and 4 m²). We recorded 95 captures of mouse opossums in 27,600 trap-nights. Our study showed that habitat type was not a significant factor for selection; instead mouse opossums selected areas with low complexity and high grass cover. The scale of analysis was also important since the selection was stronger in larger areas. Habitat selection by T. pallidior occurred mainly during the dry season. During the wet season, the species used all habitat areas and types indistinctly. The present study highlights the importance of performing analyses which include multiple spatial and temporal scales for a better understanding of the patterns involved in habitat use and species distribution.     

Habitat use of breeding birds in Central European reed beds

Wetlands Ecology and Management - To date, there have been few comprehensive studies on habitat preferences of wetland bird communities focusing on European reed bed avifauna. During the years...     

Resource use by the dryad butterfly is scale-dependent

The factors shaping the ways in which animals use resources are a key element of conservation biology, but ecological studies on resource use typically neglect to consider how the study’s spatial scale may have affected the outcomes. We used the dryad butterfly, inhabiting xerothermic grassland and wet meadow, to test for differences in its resource use at two scales–habitat patch and landscape. Based on records of plant species composition from random points within four habitat patches and from points in 53 patches along surveyed transects, we compared the microhabitat preferences of the butterfly on the patch scale, and species occurrence and abundance patterns on the landscape scale. We distinguished four main groups of factors related to vegetation structure which affected the butterfly’s resource use—factors having similar effects on both spatial scales, factors operating primarily on one of the scales considered, factors relevant only on a single spatial scale, and factors operating on both scales but with effects differing between the two habitat types. We suggest that invertebrates may respond on two spatial levels or on only one, and conclude that larger-scale studies can meet the challenges of a sophisticated metapopulation approach and can give insight into the habitat characteristics affecting the persistence of species in landscapes. We stress the value of large-scale studies on species’ habitat preferences when planning conservation strategies, while pointing out that small-scale studies provide useful information about species ecology and behavior, especially if conducted in multiple habitats.     

The winter distribution of seed-eating birds: habitat structure, seed density and seasonal depletion

To understand the reasons for population change we need to understand the mechanisms through which it occurs. Throughout western Europe there have been declines in farmland birds. These declines have been paralleled by major changes in agricultural management. Which have resulted in major changes in habitat structure. This paper describes the habitat selection at two scales (within and between fields) of a number of seed-eating farmland birds. Habitat preferences for most species were related to the density of seeds present. Which differed markedly between habitats. Seed density declined with distance from hedgerow in cultivated fields but not stubble fields. Yellow hammers were restricted to foraging close to hedgerows, whilst skylarks foraged in the centre of fields, but moved closer towards the edges as the winter progressed and seed densities declined. This work has clear consequences for agricultural management and the conservation of declining bird populations.     

Habitat use by beech martens in a fragmented landscape

We investigated key habitat features used by beech martens occupying a fragmented agricultural landscape. Locations of eight martens were radio-monitored daily for 4–12 months each. We evaluated the selection of home ranges within a geographic area, as well as the selection of habitat features within home ranges, using random simulations for comparison. Home ranges included more wood and scrub vegetation, and less arable land, than random simulations. They also included a higher proportion of watercourses with continuous vegetation along their verges, and were closer to these watercourses than random simulations. Within home ranges, beech martens used wood and scrub vegetation, and farm buildings, more intensively than expected, and arable land less than expected. On average, beech martens stayed close to watercourses (where most of the wood vegetation occurred) but not to farm buildings, indicating that only the former shaped beech marten movements. By these findings, arable land appeared to act as a seldom traversed barrier, making farm buildings uneasy to reach if they are located far from watercourses.     

Habitat use under latent predation risk. A case study with wintering forest birds

We test whether the spatial distribution of birds within a habitat is determined by predation risk and also by interspecific competition. The work was carried out in a montane mixed forest of central Spain with four Parus species, the long-tailed tit ( Aegithalos caudatus ) and the nuthatch ( Sitta europaea ). Experimental feeders, that varied in their risk of predation, were used to control the effect of natural variations in food availability and quality on the habitat use patterns of different species. Tree gleaning passerines avoided feeding on dark inner forest places far from edges, distant from protective cover, outside the inner tree canopy and near the ground; they preferred deciduous, relatively clear forest plots. These effects remained invariable across years and weather conditions. There was a common pattern of selection of foraging locations by the four Parus species: proximity to cover and height above ground and over the lowest branches of the tree canopy positively influenced the use of feeding places. According to these patterns, the vigilance proportion of species was significantly higher when feeding far from cover than when birds were feeding near pine foliage. This pattern was also common for the four studied Parus species. Nevertheless, the interspecific dominance hierarchy of the species was positively correlated with the use of the safest feeders (feeders farther the ground and nearer from protective cover within tree canopy), being the converse with the most exposed ones. Therefore, the results of this paper demonstrate that the selection of feeding locations within habitat follows a pattern minimizing predation risk. Interspecific dominance hierarchies can lead to the exploitation of unfavourable risky patches by subordinate species.     

Habitat use by chevron skinks (

Habitat use of the endangered chevron skink (Oligosoma homalonotum) was investigated between 1997 and 2002 at three sites on Great Barrier Island, New Zealand. Habitat preferences were determined by pitfall trapping and radio-tracking studies, and a comparison of catchments with and without chevron skinks. Over the course of the research, 88 skinks were encountered. Significantly more skinks were caught in pitfall traps set in stream habitat than in alluvial terrace, boulder bank or ridge habitat. Eight chevron skinks were radio-tracked for periods between three and eight days, and 118 fixes were taken from 55 different retreat sites. When compared with randomly selected sites, chevron skinks were more likely to be found at sites that had crevices, debris dams and trees than those that did not. The further a site was away from the stream edge, the less likely it was to be a chevron skink retreat site. Chevron skinks were more likely to be found in catchments with narrow streams with rocky, as opposed to silty, substrates. We recommend that future management of chevron skinks incorporate sites that contain mature forest and rocky streams. While forest habitats on Great Barrier Island appear to be increasing in area, chevron skinks may still be declining due to the effects of introduced predators.     

Habitat fragmentation and population extinction of birds

It has not been established that a major cause of extinction in birds or any other taxa is failure of metapopulation dynamics: the collapse of a network of ephemeral but discrete populations as movement between them becomes increasingly infrequent. The few data on who goes where and who mates with whom suggest that most species are structured as either a single large population or a small set of source populations and a larger set of sinks. The extinction of the latter is irrelevant to the persistence of the species. However, regional decline of a species in the face of habitat destruction and fragmentation can mimic a failure of metapopulation dynamics, because distinct aggregations of individuals will disappear much as they would if populations in an interacting network were eliminated one by one. Any species with highly restricted range is at great risk of extinction from spatially localized forces, such as cyclones or deforestation. Restricted range rather than inherent weakness is the main reason that so many island species have gone extinct or are endangered. Species with small populations in contact with much larger heterospecific ones with which they are interfertile are threatened with extinction by hybridization. Finally, the disappearance of a species from a site may be due to subtle habitat change, even if this observation seems superficially consistent with some general population theory, such as the dynamic equilibrium theory of island biogeography. Current theory is an inadequate substitute for intensive field studies as a means to address the conservation problems of individual species.     

Habitat use,abundance, and persistence of Neotropical migrant birds in a habitat matrix in northeast Belize

ABSTRACT To ensure adequate protection of nonbreeding habitats used by Neotropical migratory landbirds, we must first address questions about habitat use and quality. On the Yucatan peninsula, migrants use many habitats, several of which remain unstudied, and methodological differences preclude interhabitat comparisons based on studies to date. We used distance sampling along line transects in six habitats in northeast Belize to examine use of previously unstudied habitats (e.g., salt marsh) by Neotropical migrants and to permit comparison across habitats. We calculated unadjusted and adjusted (for detectability) density estimates for individual migrant species and for all species combined to generate hypotheses about habitat quality based on the assumption that density and quality are positively correlated. Adjusted density estimates for all migrants were highest in black mangrove habitat (1799 ± 110 ind/km²), intermediate in three forest types and milpa (range 598–802 ind/km²), and lowest in salt marsh (207 ± 32.3 ind/km²). By combining density estimates with habitat availability in our study region, we estimated that evergreen forest and black mangrove supported 70% and 9% of the region's migrant population, respectively. At the species level, five of the 10 most common species had habitat preferences (>50% detections in one habitat). Given the diversity of habitat preferences among species and apparent seasonal movements, our results indicate that Neotropical migrants in northeast Belize are dependent on a matrix of interconnected habitats.     

Habitat associations of British breeding farmland birds

Capsule Territory distribution for ten species was most strongly positively influenced by the presence of hedges and woodland edge.

Aims To describe and rank the importance of different habitat predictors on the distribution of bird territories.

Methods We derived territory maps for ten bird species across 25 sites on English lowland farmland in 2002. We related habitat predictors to the distribution of these species using information theoretic methods.

Results Habitat predictors were ranked as follows (numbers in parentheses indicate the number of species with a strong effect): hedge presence (8), boundary height (7), woodland edge (6), tree presence in boundary (4), brassica (mainly oil seed rape) (3), within‐field vegetation height (3), boundary strip (3), boundary width (3), tilled fields (3), winter set‐aside (2), ditch (1), winter stubble fields (1).

Conclusions Non‐cropped habitats had the most consistent positive effects across all ten species, with crop types and their margins exerting smaller effects.     

Habitat assessment by parasitoids: mechanisms for patch use behavior

Animals foraging for patchily distributed resources may optimizetheir foraging decisions concerning the patches they encounter,provided that they base these decisions on reliable informationabout the profitability of the habitat as a whole. Females ofthe parasitoid Lysiphlebus testaceipes exploit aphid hosts,which typically aggregate in discrete colonies. We show herehow between-colony travel time and the number of aphids in previouslyvisited colonies affect parasitoid foraging behavior. We firstassumed that parasitoids use travel time and previous colonysize to estimate a mean rate of fitness gain in the habitatand derived quantitative predictions concerning the effect ofthese two variables on patch residence time and patch-leavingrate of attack. We then tested these theoretical predictionsin laboratory experiments in which female parasitoids were allowedto visit two successive colonies. As predicted, the observedresidence time in the second colony increased with increasingtravel time and decreasing size of the first colony. Patch-leavingrate of attack decreased with increasing travel time but wasnot affected by previous colony size. These results suggestthat parasitoids use these two variables to assess habitat quality.However, discrepancies between the data obtained and quantitativepredictions show that the effect of travel time on patch usemay be more complex than assumed in our model.     

Habitat use by three rat species (

The relative abundance of ship rats (Rattus rattus), Norway rats (R. norvegicus), and Pacific rats (R. exulans), was measured in four vegetation types on Stewart Island/Rakiura, over six consecutive seasons. Ship rats were found in all four vegetation types and dominated in podocarp-broadleaf forest and riparian shrubland. Norway rats were most common in subalpine shrubland and Pacific rats dominated in manuka (Leptospermum scoparium) shrubland. Analysis of micro-habitat affinities for the three species showed that ship rats were habitat generalists. Norway rats were associated with plants of damp sites. Pacific rats showed a significant positive relationship with increasing amounts of the ground cover wire rush, (Empodisma minus). Reasons for the observed habitat use on Stewart Island could include physiological adaptation to cold and wet conditions in Norway rats; the avoidance of predation or inter-specific competition by Pacific rats; and possibly preference for more structurally complex vegetation types by ship rats.     

Habitat use by three rat species (

Ship rats (Rattus rattus) were removed from sites on Pearl Island, southern Stewart Island, in 2004 and 2005, to test whether they excluded Pacific rats (R. exulans) or Norway rats (R. norvegicus) or both from podocarp-broadleaf forest. As predators can influence habitat use in rodents, Pearl Island was selected because no mammalian predators of rodents are present. Rats were trapped in two other habitats to clarify rat distribution on the island and to obtain samples for stable isotope investigation of food partitioning within habitats. The experimental removal of ship rats failed, as Pacific rats were found to share forest and shrubland with ship rats. This result contrasted with the restricted distribution of Pacific rats on Stewart Island. Ship rats were ubiquitous, and appear to have been the dominant species in podocarp-broadleaf forest on Pearl Island. The largest species, the Norway rat, was trapped only on the foreshore of Pearl Island, but on Stewart Island it is more widespread. Ship rats and Norway rats were partitioning the coastal habitat by exploiting different food sources. Stable isotopic ratios (δ¹⁵N and δ¹³C) in muscle samples from Norway rats revealed a strong marine signature, suggesting intensive foraging in the intertidal zone. Ship rats trapped in the same habitat exhibited mixed terrestrial and marine sources in their diet. There was little obvious partitioning between ship rats and Pacific rats in forest, except a possible delay in breeding in Pacific rats relative to ship rats. Whether Norway rats select the intertidal zone to forage, or were excluded from forest by ship rats is unknown, but competitive exclusion is likely. Estimated densities of rats were low (2.1–5.1 rats ha^-1 in forest, 1.42 rats ha^-1 in shrubland) and similar to other New Zealand sites with low soil fertility. Further research will be required to elucidate the roles of food quality, habitat structure and predation in facilitating habitat selection in these species.