Oecologia

, Volume 171, Issue 2, pp 473–486 | Cite as

Distinct carbon sources indicate strong differentiation between tropical forest and farmland bird communities

  • Stefan W. Ferger
  • Katrin Böhning-Gaese
  • Wolfgang Wilcke
  • Yvonne Oelmann
  • Matthias Schleuning
Community ecology - Original research

Abstract

The conversion of forest into farmland has resulted in mosaic landscapes in many parts of the tropics. From a conservation perspective, it is important to know whether tropical farmlands can buffer species loss caused by deforestation and how different functional groups of birds respond to land-use intensification. To test the degree of differentiation between farmland and forest bird communities across feeding guilds, we analyzed stable C and N isotopes in blood and claws of 101 bird species comprising four feeding guilds along a tropical forest-farmland gradient in Kenya. We additionally assessed the importance of farmland insectivores for pest control in C4 crops by using allometric relationships, C stable isotope ratios and estimates of bird species abundance. Species composition differed strongly between forest and farmland bird communities. Across seasons, forest birds primarily relied on C3 carbon sources, whereas many farmland birds also assimilated C4 carbon. While C sources of frugivores and omnivores did not differ between forest and farmland communities, insectivores used more C4 carbon in the farmland than in the forest. Granivores assimilated more C4 carbon than all other guilds in the farmland. We estimated that insectivorous farmland birds consumed at least 1,000 kg pest invertebrates km−2 year−1. We conclude that tropical forest and farmland understory bird communities are strongly separated and that tropical farmlands cannot compensate forest loss for insectivorous forest understory birds. In tropical farmlands, insectivorous bird species provide a quantitatively important contribution to pest control.

Keywords

Stable isotopes Habitat fragmentation Pest control Feeding guilds Foraging movements 

Supplementary material

442_2012_2422_MOESM1_ESM.doc (524 kb)
Supplementary material 1 (DOC 524 kb)

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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Stefan W. Ferger
    • 1
    • 2
    • 3
  • Katrin Böhning-Gaese
    • 1
    • 2
    • 3
    • 4
  • Wolfgang Wilcke
    • 5
  • Yvonne Oelmann
    • 6
  • Matthias Schleuning
    • 1
    • 2
    • 3
  1. 1.Department of Ecology, Institute for ZoologyJohannes Gutenberg-UniversityMainzGermany
  2. 2.Biodiversity and Climate Research Centre (BiK-F)Frankfurt (Main)Germany
  3. 3.Senckenberg Gesellschaft für NaturforschungFrankfurt (Main)Germany
  4. 4.Department of Biological SciencesJohann Wolfgang Goethe-UniversityFrankfurt (Main)Germany
  5. 5.Geographic InstituteUniversity of BerneBernSwitzerland
  6. 6.Geoecology/GeographyUniversity of TübingenTübingenGermany

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