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Using high-resolution remote-sensing to quantify nest site characteristics of white-backed vulture (Gyps africanus) in Karingani Game Reserve, Mozambique
Author(s)
Lautenbach, Tom
Date Issued
2024
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
he decline of White-backed Vultures (WbVs), a critically endangered species, in southern Africa
calls for urgent intervention and an increased understanding of their nesting requirements to
improve conservation of suitable nesting trees. There is currently little research on the nesting
preferences of WbVs, and few measurements on how variation in individual tree architectures or
the surrounding area influences WbV nest site selection. Moreover, current methods of tree
measurement are time-consuming, susceptible to inaccuracy due to human error, and potentially
dangerous. This study aimed to fill these critical knowledge gaps by combining remotely sensed
Light Detection and Ranging (LiDAR) data and Red-Green-Blue (RGB) imagery with helicopter
surveys of nest locations (n=30) to explore nest site selection of WbVs in Karingani Game
Reserve (KGR), Mozambique. The LiDAR and RGB orthomosaics allowed for precise and
accurate measurement of various tree-level characteristics: canopy height, canopy area, canopy
roughness, nest orientation and peripheral position, and distance to water. Surrounding
vegetation cover was also measured, along with surrounding canopy height, and vegetation
roughness within 100 m of nesting trees. A Resource Selection Function (RSF) analysis was used
to determine which variables WbVs favoured when selecting a nesting tree. This study found that
WbVs in KGR prefer nesting in trees with an average height of 14 m (10.58 m - 16.34 m), with
large variation and roughness within their canopy (4.04s), and large canopy area, averaging
161.58m². White-backed Vultures in KGR were found to position their nests on the northern side
of the tree, but with no preference for nest position in relation to canopy edge. The approach of
using LiDAR and RGB imagery was found to be effective for measuring tree-level variables in a
time-effective and accurate manner, while revealing more information on the nesting ecology of
WbVs in KGR. This approach allowed us to gain a better understanding of the specific
requirements of WbVs when selecting a tree to nest in, and thus aid protected area management
by providing valuable information regarding the need to conserve specific habitats within
protected areas to ensure the survival of this species. This novel approach could become the new
standard for measuring trees for large raptor studies, allowing researchers to collect data from
much larger areas and increased sample sizes with ease.
calls for urgent intervention and an increased understanding of their nesting requirements to
improve conservation of suitable nesting trees. There is currently little research on the nesting
preferences of WbVs, and few measurements on how variation in individual tree architectures or
the surrounding area influences WbV nest site selection. Moreover, current methods of tree
measurement are time-consuming, susceptible to inaccuracy due to human error, and potentially
dangerous. This study aimed to fill these critical knowledge gaps by combining remotely sensed
Light Detection and Ranging (LiDAR) data and Red-Green-Blue (RGB) imagery with helicopter
surveys of nest locations (n=30) to explore nest site selection of WbVs in Karingani Game
Reserve (KGR), Mozambique. The LiDAR and RGB orthomosaics allowed for precise and
accurate measurement of various tree-level characteristics: canopy height, canopy area, canopy
roughness, nest orientation and peripheral position, and distance to water. Surrounding
vegetation cover was also measured, along with surrounding canopy height, and vegetation
roughness within 100 m of nesting trees. A Resource Selection Function (RSF) analysis was used
to determine which variables WbVs favoured when selecting a nesting tree. This study found that
WbVs in KGR prefer nesting in trees with an average height of 14 m (10.58 m - 16.34 m), with
large variation and roughness within their canopy (4.04s), and large canopy area, averaging
161.58m². White-backed Vultures in KGR were found to position their nests on the northern side
of the tree, but with no preference for nest position in relation to canopy edge. The approach of
using LiDAR and RGB imagery was found to be effective for measuring tree-level variables in a
time-effective and accurate manner, while revealing more information on the nesting ecology of
WbVs in KGR. This approach allowed us to gain a better understanding of the specific
requirements of WbVs when selecting a tree to nest in, and thus aid protected area management
by providing valuable information regarding the need to conserve specific habitats within
protected areas to ensure the survival of this species. This novel approach could become the new
standard for measuring trees for large raptor studies, allowing researchers to collect data from
much larger areas and increased sample sizes with ease.
Additional information
Thesis (Master of Conservation Science)--Cape Peninsula University of Technology, 2024
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