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   Location:Home > Research > Research Progress
Hunting increases bird extirpation in fragmented landscapes of Xishuangbanna
Author: Rachakonda Sreekar
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Update time: 2015-01-05
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Both forest fragmentation and hunting are known drivers of regional extinction of vertebrate species. However, many studies only address the effects of forest fragmentation on species extirpations and the understanding of their independent effects is poor. Dr. Rachakonda Sreekar, together with his advisors and colleagues of Xishuangbanna Tropical Botanical Garden (XTBG), conducted a study to partition the effects of hunting and forest fragmentation on bird extirpations.

The researchers examined the influence of both hunting and forest fragmentation on birds in Xishuangbanna, a species-rich region where tropical forests are hunted and have been recently fragmented by expanding monoculture rubber plantations. They focused on the area within a 10-km radius of XTBG. They compiled data on birds recorded between 1954 and 1983 before forest loss and compared it with a checklist prepared between 2011 and 2014.

To separate the effect of hunting from that of forest loss, the researchers used matrix-calibrated and countryside matrix-calibrated species–area models (SAMs) to estimate the slope of forest bird extirpations in the landscape. They then compared it with the expected species-area slope for birds in the absence of hunting.

To determine those that best explained bird extirpation probability, the researchers measured six life history and ecological traits. The six traits were forest specialization (specialist or non-specialist), mean body size (bill to tail length), habitat breadth (observed number of habitats a species occurs in; range 1–8), primary diet type (frugivore, insectivore, carnivore, granivore, nectarivore), diet breadth (number of items recorded in its diet; range 1–5) and minimum clutch size.

A total of 153 resident diurnal terrestrial bird species were recorded between 2011 and 2014, in comparison to the 231 species recorded in the past. The researchers thus estimated that 34% of bird species had been locally extinct in Xishuangbanna..

The study revealed that extirpation rates of forest birds were around 1.3 to 1.6 times higher than expected due to forest fragmentation only. Similarly, for forest frugivores that are preferred by hunters, extirpation rates were around 1.7 to 2.1 times higher than expected. However, forest understorey insectivores that are the most sensitive bird group to forest fragmentation but not hunting had extirpation rates similar to the expected rate. Extirpation probability of birds increased with body size, and did not differ between forest and non-forest birds.

  Using species-area relationships, the effects of area and hunting on regional extinction of birds were separated. Given evidence of past and present hunting activity in Xishuangbanna, and the lack of support for alternative explanations, the researchers suggested that hunting increased forest bird extirpations in fragmented landscape. More conservation interventions should be considered.

   The study entitled “The use of species–area relationships to partition the effects of hunting and deforestation on bird extirpations in a fragmented landscape” has been published online in Diversity and Distributions.

Casque of a Rufous-necked Hornbill (Image by Rachakonda Sreekar)

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Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences. Menglun, Mengla, Yunnan 666303, China
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