Breeding bird species richness in Taiwan: distribution on gradients of elevation, primary productivity and urbanization
Resource
Journal of Biogeography 31: 307-314
Journal
Journal of Biogeography 31
Journal Volume
31
Journal Issue
2
Pages
307-314
Date Issued
2004
Date
2004
Author(s)
Abstract
Aim: To examine the richness of breeding bird species in relation to elevation, primary productivity and urbanization. Location: The island of Taiwan (120°-122° E, 22°-25° N). Methods: We arranged bird species richness (BSR) data from 288 bird censuses undertaken in Taiwan into a 2 x 2 km quadrat system and calculated average values of elevation, primary productivity [surrogated by normalized difference vegetation index (NDVI)], and urbanization (surrogated by road density and percentage of built area) for each 2 x 2 km quadrat. Results: Bird species richness showed a hump-shaped relationship with elevation. It increased with elevation from sea level (10-64 species per 2 x 2 km quadrat), peaked around 2000 m (43-76 species), and then decreased with elevation towards its minimum at the highest elevation. Road density and percentage of built area decreased with elevation, and NDVI showed a hump-shaped relationship with elevation and inverse relationships with road density and percentage of built area. BSR increased with NDVI and decreased with road density and percentage of built area. Linear and cubic terms of elevation together explained 31.3% of the variance in BSR, and road density explained additional 3.4%. The explanatory power of NDVI on BSR was insignificant after the effects of elevation and road density had been justified. Main conclusions: We argue that urbanization plays an important role in the BSR of Taiwan. Urbanization might indirectly decrease BSR through decreasing primary productivity and therefore change the hypothetical inverse relationship between BSR and elevation into a hump-shaped relationship. We also propose a time hypothesis that the biotic communities in the mid-elevation zone of Taiwan had relatively longer periods of existence during the Pleistocene glacial cycles, which might be one underlying process of the observed hump-shaped relationship between species diversity and elevation.
Subjects
Elevation; Energy limitation theory; Landbridge; Macroecology; Primary productivity; Species richness; Time theory; Urbanization
Other Subjects
avifauna; biogeography; elevation; macroecology; primary production; species richness; urbanization; Asia; Eurasia; Far East; Taiwan; Aves
Type
journal article
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