Spatial and temporal fluctuations in bird communities along a forest-farmland gradient in western Kenya

The impacts of human activities, notably the conversion of tropical forests into farmland habitat, has profound impacts on biological diversity and ecosystem functions (Millennium Ecosystem Assessment 2005). It is widely debated to what extent human modified landscapes can maintain tropical biodiversity and their ecosystem functionality (e.g. Waltert et al. 2004, Sekercioglu et al. 2007). In this thesis, I have used a huge and temporarily replicated dataset to assess the value of different habitat types differing in land-use intensities for bird communities in tropical East Africa. I investigated bird abundance and species richness along a forest-farmland habitat gradient and assessed spatial and temporal fluctuations of bird assemblages and their food resources. I could show that forest and farmland habitats harbor distinct bird communities. Moreover, the protection of natural forests merits the highest priority for conserving the high diversity of forest-dependent bird species. My study, however, also shows that farmland habitats in the proximity of natural forest can support a high bird diversity. High bird diversity in tropical farmlands depends on a high structural complexity, such as in small-scale subsistence farmlands. From my findings, I conclude that the conversion of forest to farmland leads to substantial losses in bird diversity, in particular in specialized feeding guilds such as insectivores, while the conversion of structurally heterogeneous subsistence farmlands to sugarcane plantation causes erosion of bird diversity in agricultural ecosystems. Both findings are important for conservation planning in times when tropical forests and agroecosystems are under constantly high pressure due to increasing human population numbers and global demands for biofuel crops (Gibbs et al. 2008). From an ecosystem function perspective, my study demonstrates the potential of agroecosystems in supporting important ecosystem functions, such as seed dispersal by frugivorous birds and pest control by insectivorous birds. I could show that bird abundances in both frugivorous and insectivorous guilds were strongly predicted by their respective food resources, implying that seasonal shifts in fruit and invertebrate abundance at Kakamega forest and surrounding farmlands affect community dynamics and appear to influence local movement patterns of birds. The most interesting finding of this study was that feeding guilds responded idiosyncratically to resource fluctuations. Frugivore richness fluctuated asynchronously in forest and farmland habitats, suggesting foraging movements and fruit tracking across habitat borders. In contrast, I found that insectivores fluctuated synchronously in the two habitat types, suggesting a lack of inter-habitat movements. I therefore predict that insectivorous bird communities in this forest-farmland landscape may be more susceptible to the combined effects of land-use and climate change, due to their narrow habitat niche and limited capacity to track their resources. The fact that a number of bird species regularly moved across the landscape mosaic in my study system implies that birds are able to provide long-distance seed dispersal across habitat borders. Thus, birds may enhance forest regeneration in human-modified landscapes, such as those in most parts of tropical Africa, given that forest remnants are protected within an agricultural habitat matrix. In order to effectively conserve tropical biodiversity within forest-farmland mosaics, this study advocates for conservation strategies that go beyond forest protection and explicitly integrate farmlands into forest management plans and policies. This should emphasize the retention of keystone habitat elements within tropical farmland landscapes, such as indigenous trees, forest galleries and hedgerows, whose presence enhance species diversity. Such grassroot-level approaches can be operationalized for instance through providing incentives to farmers to maintain their traditional subsistence land-use practices and through community-based livelihood projects aiming at enhancing local habitat heterogeneity and inter-habitat connectivity

East African coastal forest under pressure

The Arabuko Sokoke dryland coastal forest along the East African coastline provides a unique habitat for many endangered endemic animal and plant species. High demographic pressure with subsequent land-splitting, soil depletion in combination with erratic rainfalls and the collapse of the tourism industry are negatively affecting food security and human livelihood quality in this region. Food crops were originally produced by subsistence farming, but have now to be purchased at local-and super-markets, constituting a major financial burden for the local people. In consequence, overexploitation of natural resources from Arabuko Sokoke forest (illegal logging, charcoal burning, poaching of wild animals) increased during the past years. In this commentary we document ecosystem heterogeneity leading to high species richness. We discuss direct and indirect drivers of habitat degradation of the Arabuko Sokoke forest, and critically reflect current and future solutions. Key drivers of habitat destruction and biodiversity loss are (i) illegal timber logging and removal of woody biomass, (ii) poaching of bush-meat, (iii) exceeding of the carrying capacity by the local elephant population, restricted to Arabuko Sokoke by an electric fence, and (iv) weak governance structures and institutional confusion exacerbating illegal exploitation of natural resources. Potential solutions might be: Provisioning of additional income sources; reforestation of the surrounding areas in the framework of REDD+ activities to create a buffer around the remaining primary forest; improving governance structures that formulates clear guidelines on future usage and protection of natural resources within the Arabuko Sokoke forest; and family planning to counteract human demographic pressure and the exploitation of natural resources

Current conservation status of the Blue Swallow Hirundo atrocaerulea Sundevall 1850 in Africa

The global Blue Swallow Hirundo atrocaerulea was classified as Vulnerable in 2010 on account of its small and rapidly declining population estimated at less than 1 500 pairs. We undertook this study to gain a better understanding of the current status and threats facing this migratory species. Three previously unknown areas that might be part of the species’ non-breeding range were identified in Kenya and northern Tanzania. Within its breeding range we identified three previously unknown areas of potentially suitable habitat, one in Tanzania and two in Malawi, which require further exploration. Population viability assessment predicted that the Blue Swallow population will decline by 8% in 10 years. The overall probability of extinction of the species in the wild is 3%. Minimum viable population size analysis suggests that a goal for the long-term conservation of the Blue Swallow should be to mitigate current threats that are driving declines such that the population increases to a minimum of 3 600 individuals. This should consist of at least 900 individuals in each of the four clusters identified, along with a minimum of 500 individuals in at least one of the meta-populations per cluster. The four clusters are located in (1) the southeasten Democratic Republic of the Congo, (2) highlands of southern Tanzania and northern Malawi, (3) eastern highlands of Zimbabwe and (4) South Africa and Swaziland. The current proportions of the Blue Swallow population in strictly protected and unprotected areas on their breeding grounds are 53% and 47%, respectively, whereas on their non-breeding grounds the corresponding percentages are 25% and 75%, respectively. Our reassessment of the Blue Swallow’s risk of extinction indicates that it continues to qualify as Vulnerable according to the IUCN/SSC criteria C2a(i).http://www.tandfonline.com/loi/tost202016-09-30hb2016Zoology and Entomolog

Status of the endangered Spotted Ground Thrush Zoothera guttata fischeri in coastal Kenya forests

Volume: 27Start Page: 19End Page: 3

Nature conservation at the edge

Currently, there is an increasing need for evidence-based strategies in nature conservation, for example when designing and establishing nature reserves. In this contribution, we critically assess the ecological relevance of recent nature conservation practices in Kenya (East Africa), a region of global biodiversity hotspots. More specifically, we overlay the distribution of species richness (here based on mammals, birds, amphibians and vascular plants) with the location of nature reserves, the Kenyan agro-ecological zones (areas representing diverging agricultural potentials), and with the spatial distribution of human population density. Our analyses indicate that the majority of protected areas are located in areas with comparatively low species richness, while areas with extraordinary high levels of species richness are not adequately covered by nature reserves. Areas of high agricultural productivity (and with high human demographic pressure) are mainly reserved for high-yield agriculture; however, these regions are also characterised by high species richness. The majority of nature reserves are restricted to the semi-arid regions of Kenya, marginal for agricultural usage, but also with low levels of species richness. Based on this analysis, we prioritize areas for future protection. This single-country case illustrates that agricultural production in high-yield areas outweighs nature conservation goals, even in global biodiversity hotspot regions, and that priority setting may conflict with effective nature conservation

Population genetics of the East African White-eye species complex

The Eastern Afromontane biodiversity hotspot consists of isolated mountain massifs embedded within the dry lowland savannas of East Africa and of which the peaks and ridges are covered by cloud forest remnants. These cloud forests are home to the Mountain White-eye (Zosterops poliogaster), while three congeneric species (Abyssinian White-eye, Zosterops abyssinicus; Yellow White-eye, Zosterops senegalensis; Pemba White-eye, Zosterops vaughani) inhabit the adjacent lowland savannas. We sampled individuals of all four species across Kenya to analyse interspecific genetic relationships as well as intraspecific differentiation among mountain populations of Z. poliogaster. While the level of genetic differentiation among the four species was rather low, genetic differentiation within Z. poliogaster was very high, even between geographically neighbouring populations. Overall, levels of genetic variation varied strongly across all four species, with much higher diversity detected within the three lowland ones. The highland species was characterised by numerous private alleles that were geographically restricted at populations from single mountains, some of which showed evidence of recent population bottlenecks. We conclude that Z. poliogaster populations are both of high conservation value and conservation concern, given the high proportion of endemic alleles and the genetic signatures of high genetic drift and low gene flow that are typical for small and isolated populations

More topics from the tropics : additional thoughts to Mammides et al.

Most studies on tropical conservation questions are conducted by researchers of developed countries from the north. This geographic disconnection was recently criticised by Mammides et al. Here, we reflect on their findings and add further views from scientist's and journal editor's perspectives. We argue that journals are, a priori, most strongly interested in research questions and approaches that will likely increase their scientific impact and prestige. This is rarely compatible with publishing articles on questions with restricted global impact or based on single taxa. We question whether small changes in the editorial policy of international conservation journals will considerably improve the geographic diversity in key conservation publications. Rather, thematic scopes of the leading conservation journals should be modified, preferably in close collaboration with leading conservationists from the south. We are convinced that long-term investments in the tropics will create a stronger local scientific community, thus bolstering academic morale, and finally may lead to an increase in the submission and acceptance rate of articles written from scientists from these regions

Appendix S1_Dryad_Heredity_Habel et al.

Allele frequencies of microsatellite