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Kariuki Ndang'Ang'A P.,BirdLife International Africa Partnership Secretariat | Kariuki Ndang'Ang'A P.,Jomo Kenyatta University of Agriculture and Technology | Njoroge J.B.M.,Jomo Kenyatta University of Agriculture and Technology | Ngamau K.,Jomo Kenyatta University of Agriculture and Technology | And 3 more authors.
Bird Study | Year: 2013

Capsule Most birds in a Kenyan highland agroecosystem foraged from the ground, potentially contributing to weed regulation, and invertebrate intake rates by aerial foraging insectivores were high, indicating that birds could contribute to pest regulation. Aims Bird foraging behaviour and its implications for provision of ecosystem services and crop damage was investigated. Methods Detailed observations of foraging birds in relation to substrates used and food items consumed were undertaken within cultivated areas during dry and wet seasons. Results Most birds foraged from the ground, often consuming seeds, fruits and flowers from weeds rather than crop plants. The relatively high rate of invertebrate intake by two aerial foraging species and the high number of insectivorous bird species recorded in the area suggest that invertebrate predation could also be high and potentially contribute to pest regulation. Species-specific differences in the habitats birds used and prey taken were also identified, providing an indication of species likely to contribute to invertebrate and weed pest control and those likely to cause crop damage. Conclusion The results describe species-specific avian foraging behaviour in African farmland that may be used in informing agricultural management practices to enhance beneficial species and reduce impacts of crop-damaging ones. © 2013 Copyright British Trust for Ornithology.


Ndang'ang'a P.K.,BirdLife International Africa Partnership Secretariat | Ndang'ang'a P.K.,Jomo Kenyatta University of Agriculture and Technology | Njoroge J.B.M.,Jomo Kenyatta University of Agriculture and Technology | Githiru M.,Ornithology Section
Ostrich | Year: 2013

We examined the effects of vegetation composition and structure on bird species diversity and richness of foraging guilds in the highland agricultural landscape of Nyandarua, Kenya. Bird point counts and vegetation surveys were undertaken during four sampling periods. Linear mixed models were used to examine the effects of vegetation variables on bird species diversity and richness of respective foraging guilds, and logistic generalised linear models used to examine vegetation effects on the presence/absence of the 17 most common bird species. Bird species diversity increased with increasing density of woody plant species and vegetation structural heterogeneity. Two gradients of increasing vegetation structural heterogeneity were most important in influencing bird community composition and had positive effects on species diversity and the presence of most of the species assessed: (1) increasing closed cover due to woody plant density, which also had positive effects on species richness of frugivores and nectarivores, but negative effects on carnivores, and (2) increasing fallow and cultivation versus decreasing grassland/pasture cover, which also had a positive effect on species richness of granivores and omnivores. This study reaffirms the need to maintain a structurally rich agricultural landscape for it to support agrobiodiversity. © 2013 Copyright © NISC (Pty) Ltd.


Palla F.,University Pierre and Marie Curie | Picard N.,CIRAD | Abernethy K.A.,Institute Of Recherche En Ecologie Tropicale | Abernethy K.A.,University of Stirling | And 7 more authors.
Plant Ecology and Evolution | Year: 2011

Background and aims - The Lopé National Park in Gabon, recently added to the UNESCO world heritage list, presents a mosaic of forest and savanna that dynamically changes. Conserving this landscape requires an understanding of the forest dynamics. This study aims at defining a forest typology at Lopé in relation with its dynamics. Methods - Floristic and structural characteristics for 265 tree species belonging to 55 families were measured in 258 sampling plots in the Lopé National Park. Multivariate analysis of these data was used to partition the sampling plots into groups on the basis of their floristic or structural characteristics. Key results - Five structural forest types and six floristic forest types were identified. This typology showed that the forests in the forest-savanna mosaic of Lopé organize themselves along a gradient of forest recovery, from young forests to mature forests. Typical pioneer species are associated with the youngest forest stages. The gradient on the species also corresponds to a geographical gradient on the sampling plots, associated with features like altitude, rocks, or hydrography. Conclusions - Five forest types were defined on the basis of species abundances. The snapshot of forest types characterizes a dynamic process of forest regeneration. © 2011 National Botanic Garden of Belgium and Royal Botanical Society of Belgium.


Ndang'ang'a P.K.,BirdLife International Africa Partnership Secretariat | Ndang'ang'a P.K.,Jomo Kenyatta University of Agriculture and Technology | Njoroge J.B.M.,Jomo Kenyatta University of Agriculture and Technology | Vickery J.,The Royal Society for the Protection of Birds
International Journal of Pest Management | Year: 2013

Bird exclusion experiments on kale (Brassica sp.) plants were undertaken to quantify the extent to which foraging birds contributed to reducing the densities and impact of invertebrate pests. During the dry season, significantly higher leaf-area loss, aphid and thrips abundance were recorded in bird-excluded compared with control plants, suggesting that birds could make an important contribution to pest control. On average, per week, during the dry season, exclusion of birds from kale plants led to both a marked increase (130%) in the number of leaves infested with aphids and an increase in leaf damage by pests (about three times greater than when birds had access to the kale plants). These results suggest that, in the dry season, foraging birds reduce the invertebrate pest load and hence the amount of leaf damage in kale, and that this may, in turn, have an impact of the market value of the crop. We recommend that measures to enhance avian insectivory should be explored and encouraged in order to better take advantage of birds in integrated pest management of kale and possibly other crops. © 2013 Copyright Taylor and Francis Group, LLC.


Ndang'ang'a P.K.,BirdLife International Africa Partnership Secretariat | Ndang'ang'a P.K.,Jomo Kenyatta University of Agriculture and Technology | Njoroge J.B.M.,Jomo Kenyatta University of Agriculture and Technology | Ngamau K.,Jomo Kenyatta University of Agriculture and Technology | And 3 more authors.
Ostrich | Year: 2013

We examined the effects of crop diversity on avian species richness and abundance in the highland farmlands of Nyandarua, Kenya. We surveyed birds using point counts and recorded habitat data at the same locations estimating cover and growth stage of all crop types, whether they were grown as intercrops or monocrops, and the dominant surrounding vegetation type. An index of crop diversity was calculated from the percentage cover of the different crop types. The effects of these habitat variables on bird species richness, abundance of foraging guilds and the abundance of each of the 12 most common species were examined using linear mixed models. Crop diversity had significant positive effects on species richness. Cereal cover had negative effects on species richness, overall bird abundance and abundance of granivores. Occurrence of cultivation/fallow and mixed vegetation as the dominant habitat surrounding crop plots positively influenced granivores' abundance, and the abundance of Speckled Mousebird Colius striatus, a pest species, was favoured by increasing orchard cover and occurrence of wooded and shrub vegetation as the dominant surrounding vegetation type. The study confirmed that heterogeneity brought about by increased crop diversity and reduced cereal cover within cultivations contributed to enhancement of farmlands as habitats for birds. © 2013 Copyright NISC (Pty) Ltd.

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