We examined and compared territoriality and habitat use of two congeneric babbler species in Kirinyaga district, central Kenya, with the aim of explaining their differences in global conservation status. Hinde's Babbler Turdoides hindei is a scarce, globally Endangered species whereas Northern Pied Babbler T. hypoleucus is much more abundant and widespread, and occurs throughout the range of Hinde's Babbler. Our findings suggested a lack of flexibility in the choice of habitat by Hinde's Babbler, whose territories were centred on a scarce habitat type: Lantana thickets in river valleys or near swamps. The two species showed similar daily foraging ranges but Hinde's Babbler occupied smaller group territories, whose size was not related to group size. Aggressive encounters between the two species occurred over shared feeding grounds, all of which were initiated and won by Hinde's Babbler. Its dependence on Lantana thickets makes Hinde's Babbler highly susceptible to further habitat loss within its range.

The forests of the Taita Hills of south-east Kenya are of great importance to conservation, holding three endemic birds and many other endemic taxa. We surveyed birds in their remaining forest fragments in July-August 1996, and followed up these surveys with collection of remote sensing imagery of the area, an assessment of museum specimens and a thorough literature review. In this paper we assess the conservation status in the Taita Hills of their 47 species of forest birds. We conclude with general recommendations for the conservation of the area.

Fragmentation of continuous habitat blocks into small, isolated patches may cause gradual replacement of habitat specialists by generalists and edge-dwelling species, thereby altering trophic interactions within communities. When fragmentation progressively increases the edge-to-interior ratio of forest remnants, forest birds are typically exposed to higher levels of nest predation, especially so near forest edges. However, the strength and direction of this ‘edge effect on nest predation’ may vary with predator communities, which in turn can be affected by habitat type, landscape structure and geographical location. We studied avian nest predation in two isolated forest fragments in the Taita Hills of southeast Kenya, where small mammals, rather than birds, dominate predator communities. The use of artificial ground nests allowed us to reduce variation in laying date and microhabitat use, which are known to affect predation on natural nest in the study area. Predation rates did not increase near the forest boundary, but instead, were higher in the forest interior of one of the fragments. Such inverse edge effects may be caused by forest-dependent small mammals or snakes that can remove bird eggs. Although inverse edge effects may be more common in East African tropical forests than previously thought, and should therefore be taken into account when drafting conservation plans, the underlying mechanisms remain unclear. Further study of the population dynamics of small mammals and snakes, and their relative impact on nest predation in fragmented habitats, is therefore required.

The Giant Conebill Oreomanes fraseri is a specialist of high Andean Polylepis forest remnants. With the aid of radio-tracking and visual observations, the average 100% minimum convex polygon home range size of seven adult individuals was 7.15 ha. Range size decreased with increasing tree density, and for equal tree densities, it was larger in the study site with larger Polylepis fragments. Home ranges often comprised areas that were largely or entirely devoid of trees. Within home ranges, space use significantly varied with time of day, and this pattern tended to be largely consistent among days. Given the large extent of variation in size and structure already observed in this small sample of home ranges, we suggest that apart from the size, shape, structure and degree of isolation of the remaining forest patches, also their topographic location, and hence sun exposure, may be an important consideration when designing conservation strategies for Giant Conebill.

As anthropogenic stress increasingly affects the viability of natural populations of animals and plants, conservation ecologists are challenged to identify vulnerable populations before their demographic and/or genetic properties become irreversibly affected. Since traditional biomarkers of anthropogenic stress are often cumbersome to measure, and populations may thus go extinct before appropriate data can be obtained, there is a growing interest in individual-based markers that do not require repeated captures, are relatively easy to measure, and allow mitigating action one step ahead. One such marker, left-right asymmetry in bilateral symmetrical traits (“fluctuating asymmetry”, FA) has become an established bioassay of the quality and health of individuals and populations in evolutionary-ecological studies. However, the lack of a theoretical framework that predicts under which ecological conditions relationships between FA, stress and fitness can be expected, continues to hamper the use of FA in applied conservation. Here, we briefly review the concept, measurement and analysis of FA, and appraise its expediency in a selection of 21 avian studies covering environmental or genetic stress commonly encountered in conservation biology. The majority of studies met the basic statistical requirements of FA analysis, and two-thirds reported significant, positive relationships with environmental or genetic stress, although with substantial variation among traits, stresses, ages and sexes. In most cases, the observed heterogeneity in relationships with FA could be explained by taking into account both methodological and conceptual issues. Effect sizes ranged from very small (0.02) to very large (0.76), with a weighted average of 0.30, indicating that on average 9% of variance in the variable of interest was explained by FA. Given the intrinsic difficulties associated with FA analysis, conservation ecologists are advised to combine information from FA with that of other individual-based biomarkers, such as the study of growth-bar dimensions on developing feathers.

Our study focused on the Taita White-eye Zosterops silvanus, one of three bird species endemic to the Taita Hill forests, south-east Kenya. Formerly considered Critically Endangered, Taita White-eye has been down-listed to Endangered following the findings of this study. Between November 1998 and September 1999 we counted this species along line transects to establish their current population status and distribution in its entire range. White-eye censuses were conducted in nine forest fragments of the Taita Hills and the virtually undisturbed Mt Kasigau forest. The total global population of Taita White-eyes was estimated to be c. 7,100 birds. Mt Kasigau was shown to be the species' main stronghold, maintaining a very high density (26 birds ha−1) and holding 80% (5,600 individuals) of the entire population. In the Taita Hills forests, densities were consistently higher in the small isolated fragments than in the large ones, though the former held only a small population (3% of total). At Mt Sagala, a large isolated block where indigenous trees have been largely replaced with exotic plantation, this species was not encountered. We found no evidence of interchange between the White-eye populations on Mt Kasigau and the Taita Hills forests, probably because of the separation by a low-altitude, dry woodland habitat barrier. While prioritization for conservation action should focus more on the Taita Hills forest fragments, Mt Kasigau should be treated as fragile ecosystem which holds a huge, apparently insular population of Taita White-eyes.

Sound knowledge of underlying mechanisms is essential for understanding how species respond to habitat fragmentation. Because most threatened species are typically the first ones to suffer local extinctions with forest fragmentation, studying why they fare poorly at the broader landscape scale is difficult. Related, sympatric but common species may be useful surrogates if they can provide insights germane for the conservation of rarer species. We illustrate this using a case study from the highly fragmented Taita Hills forests, south-eastern Kenya, of the Critically Endangered Taita thrush Turdus helleri and the more common white-starred robin Pogonocichla stellata as the surrogate. The responses of the thrush to habitat disturbance were in the same direction as the surrogate robin (e.g. higher fluctuating asymmetry, lower effective population densities and male-biased sex ratios), albeit they were detected sooner and were more severe because of its lower dispersal capacity. The key conservation measures proposed from the surrogate study largely matched those based on an independent evaluation of the thrush data. Additionally, the surrogate provided extra insights into the potential solutions for problems facing the thrush, and provided a base that could be used as a template for restoring the thrush populations in this area. Thus, our findings support the use of surrogate species in the conservation of sympatric related species in fragmented landscapes. We contend that this approach is also applicable for allopatric related species where landscapes are similar, provided that detailed data on population patterns and processes for the surrogate are available.

Fragmentation of forests adversely affects forest-dependent biota, and conservation biologists strive to develop a good understanding of how species respond to changes associated with habitat attrition in order to establish the best conservation strategies. The spatial structure of populations persisting in fragmented landscapes governs their response to habitat fragmentation, and hence dictates the remedial actions that will be most effective for species and habitat conservation. The Taita Hills forests of Kenya are an example of a highly fragmented Afrotropical forest ecosystem embedded in a human-dominated landscape. The spatial structure of the white-starred robin Pogonocichla stellata populations living in indigenous forests across this landscape was examined. Due to its forest dependence and widespread occurrence, the robin was used as a model species to help formulate general conservation guidelines for forest-dependent species and their habitats within this landscape. Results from demographic, genetic and behavioural work point to a mixed spatial structure with elements of patchy population dynamics on a fine scale, and a core-satellite or source-pseudo-sink system on a broader scale. In particular, the findings underscore (1) the importance of dispersal, (2) the importance of small patches, (3) the importance of the largest patch, and (4) the processes underlying problems associated with forest disturbance. We examine the conservation implications of this information, and report on activities already initiated or planned, in line with these findings, for the Taita Hills.

Neotropical bats occupy a large variety of trophic niches, and represent locally abundant, species-rich communities. As such, they are highly suited as a model group for the study of temporal and spatial dynamics of animal communities. However, despite this important research potential, data on the dynamics and turnover rates of Neotropical bat communities are lacking. We here study both aspects for bats inhabiting two natural forests surrounded by savanna in Bolivia. Over a period of 8 y, both bat communities showed high rates of species turnover. As predicted, species relying on fluctuating food resources were more likely to be absent in particular years, whereas species relying on more predictable food supplies were present in all years.

The highland grasslands of central Kenya hold a suite of restricted-range bird species, including several of global conservation concern. These grasslands occur almost entirely on private land with no formal protection, and have received little conservation attention. This paper describes land-use change on the Kinangop Plateau, Kenya, and considers the implications for grassland bird species, especially Sharpe's Longclaw Macronyx sharpei. The Kinangop Plateau is an area of montane grassland east of the Rift Valley, used primarily for dairy farming since human settlement in 1964. However, dairy farming (which retains grassland as pasture) has given way to other forms of land-use, especially cultivation of crops. In March 1996, a questionnaire was administered to 50 landowners to investigate community attitudes towards birds and their conser vation, the extent of present land-use changes and likely future land-use patterns. The mean acreage of landholding was decreasing, and more grassland was rapidly being converted into cultivated land, with 3.2% being ploughed up during the six months from November 1995 to May 1996. Farmers expressed a preference for crop farming (66%) over livestock farming (26%) or other land uses. Thirty-two per cent expressed a positive attitude, and 60% were indifferent, towards birds. Most (76%) were not aware of biodiversity values or conservation. Though 64% were aware of declining bird populations around them, 82% of this group did not realize that their activities might be contributing to this decline. Sixty-eight per cent of landowners planned to convert all or part of their grassland holdings. Although landowners' interests seemed generally incompatible with grassland conservation, a substantial proportion (44%) were prepared to consider opportunities to enhance the area's conservation value. An informal follow-up survey in March 1999 concluded that prospects for the dairy industry and for grassland habitats on Kinangop were not as bleak as the initial survey suggested, but confirmed the delicate conservation status of Sharpe's Longclaw and its habitat. We suggest a variety of actions that might help to secure the future of Sharpe's Longclaw while promoting sustainable agricultural development on Kinangop, and propose several topics where further research is needed. Species such as Sharpe's Longclaw will only survive if we can develop ways of managing their habitats in a manner that is consistent, rather than in conflict, with the needs of the agricultural community.

There is growing evidence from both experimental and non-experimental studies that fluctuating asymmetry does not consistently index stress or fitness. The widely held – yet poorly substantiated – belief that fluctuating asymmetry can act as a universal measure of developmental stability and predictor of stress-mediated changes in fitness, therefore staggers. Yet attempts to understand why the reported relationships between fluctuating asymmetry, stress and fitness are so heterogeneous – i.e. whether the associations are truly weak or non-existent or whether they become confounded during different stages of the analytical pathways – remain surprisingly scarce. Hence, we attempt to disentangle these causes, by reviewing the various statistical and conceptual factors that are suspected to confound potential relationships between fluctuating asymmetry, stress and fitness. Two main categories of factors are discerned: those associated with the estimation of developmental stability through fluctuating asymmetry, and those associated with the effects of genotype and environment on developmental stability. Next, we describe a series of statistical tools that have recently been developed to help reduce this noise. We argue that the current lack of a theoretical framework that predicts if and when relationships with developmental stability can be expected, urges for further theoretical and empirical research, such as on the genetic architecture of developmental stability in stressed populations. If the underlying developmental mechanisms are better understood, statistical patterns of asymmetry variation may become a biologically meaningful tool.

Fruit-eating birds play an important role in the seed dispersal of many tropical plants (e.g. Herrera 1984), and the foraging behaviour of avian frugivores may affect their seed-dispersal capabilities (Loiselle & Blake 1999,Schupp 1993, Traveset 1994). For instance,shorter visits tend to produce less clumped seed distributions (Graham et al. 1995). Also,avian frugivores often feed on the fruits of several plant species over short periods of time (Herrera 1984, 1988a; Levey et al. 1994) in some non-random pattern (Herrera 1998). This potentially produces a predictable spatial pattern of the dispersed seeds (White & Stiles 1990). Forest destruction leads to fragmentation and degradation of the remaining habitats, which may influence patterns of adult tree distribution if the production, predation, dispersal, and/or regeneration of tree seeds is affected (Harrington et al. 1997). If dispersal of avian frugivores is disrupted by habitat fragmentation, plant species might face reduced regeneration, or even local extinction if they depend on a single, locally extinct disperser (Kellman et al. 1996). Increased predation of seeds and regenerating plants in the edges and gaps may also directly reduce regeneration rates (Corlett & Turner 1997, Harrington et al. 1997, Schupp 1988).