Vegetation composition and structure influences bird species community assemblages in the highland agricultural landscape of Nyandarua, Kenya

  • P Kariuki Ndang’ang’a
  • John BM Njoroge
  • Mwangi Githiru

Abstract

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.

Keywords: birds, East Africa, farmland, forest, grassland, heterogeneity

OSTRICH 2013, 84(3): 171–179

Author Biographies

P Kariuki Ndang’ang’a
BirdLife International – Africa Partnership Secretariat, PO Box 3502 – 00100, Nairobi, Kenya; Jomo Kenyatta University of Agriculture and Technology, PO Box 62000 – 00200, Nairobi, Kenya; Ornithology Section, National Museums of Kenya, PO Box 40658 – 00100, Nairobi, Kenya
John BM Njoroge
Jomo Kenyatta University of Agriculture and Technology, PO Box 62000 – 00200, Nairobi, Kenya
Mwangi Githiru
Ornithology Section, National Museums of Kenya, PO Box 40658 – 00100, Nairobi, Kenya
Published
2013-12-10
Section
Articles

Journal Identifiers


eISSN: 1727-947X
print ISSN: 0030-6525