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Reference: Githiru, Mwangi., (2002). Endemic forest birds of the Taita Hills. DPhil. University of Oxford.Citable link to this page:


Endemic forest birds of the Taita Hills Subtitle: Using a model species to understand the effects of forest fragmentation on small populations

Abstract: Despite intense publicity, habitat loss still remains a serious threat to biodiversity. Forest destruction is itsfrontrunner, both in terms of physical habitat under threat and potential for biodiversity loss. In thefragmented landscape of the Taita Hills, SE Kenya, several bird species are facing the threat of extinctionfrom forest loss. They are absent from many of the remnant forest patches and/or are showing negativeeffects with increasing disturbance. Using a relatively common forest-dependent bird species - the whitestarredrobin Pogonocichla stellata - as a model, the current status of this ecosystem was examined, andfuture patterns predicted in view of the unrelenting destruction. As expected, the robin population in thelargest and most intact fragment (c35 ha) was the healthiest, suggesting that this was indeed the bestquality habitat patch: it had the highest population density, highest productivity (low nest predation andhigh juvenile to adult ratio) and lowest turnover rates. Effects of forest deterioration were evident fromthe fact that the medium-sized patch (c95 ha), which is undergoing severe degradation, was a worsehabitat for the robin than the tiny patches (c2-8 ha): it had the lowest population density, lowestproductivity (highest nest predation rates and lowest juvenile to adult ratio), and highest turnover rates.The explanation for this is twofold. Besides the smallest patches facing lower levels of habitat lossrecently, they also had high levels of dispersal between them. They occasionally operated as a finegrainedsystem with individuals moving between them in the space of a few days. In general, the robinmetapopulation is demographically (rate of change, λ = 0.996) and genetically (at migration- andmutation-drift equilibrium) stable at present. The populations in the largest and smallest patches werepotential sources providing emigrants that were possibly crucial in sustaining the population in themedium-sized patch (given its low productivity and high turnover rates). Overall, these findingsunderscore the importance of within-patch processes, both for ensuring persistence of subpopulations andproviding dispersers, as well as between-patch processes (chiefly dispersal) for ensuring metapopulationpersistence. Thus, by furnishing ample sample sizes that enabled work to be carried out in all fragmentsthroughout this landscape, the model species approach was useful for identifying the need for a two-prongedconservation strategy. First, a need to focus within fragments to reduce habitat loss anddegradation, and second, to address among fragment issues relating to land-use and maintaining aforested landscape, in order to enhance connectivity between patches. Finally, based on the mechanismsby which disturbance and fragmentation are affecting bird populations e.g. predator influxes from thesurrounding matrix, conservation recommendations for the Taita Hills are offered.

Type of Award:DPhil Level of Award:Doctoral Awarding Institution: University of Oxford Notes:The digital copy of this thesis has been made available thanks to the generosity of Dr Leonard Polonsky


Lens, LucMore by this contributor



Cresswell, WillMore by this contributor



Perrins, Christopher M.More by this contributor


 Bibliographic Details

Issue Date: 2002Identifiers

Urn: uuid:b532599f-8f75-4a11-95d5-61a5afee1fca

Source identifier: 603828460 Item Description

Type: Thesis;

Language: eng Subjects: Kenya Taita Hills Fragmented landscapes Forest birds Tiny URL: td:603828460


Autor: Githiru, Mwangi. - institutionUniversity of Oxford facultyLife and Environmental Sciences Division - - - - Contributors Lens, Luc

Fuente: https://ora.ox.ac.uk/objects/uuid:b532599f-8f75-4a11-95d5-61a5afee1fca


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