Yellow-billed Kite Milvus aegyptius nesting dynamics and breeding success across a human-modified landscape

Anthropogenic habitat transformation is one of the leading causes of biodiversity decline. Migratory birds, particularly many raptor species, are increasingly threatened by global environmental change. We investigated the nesting dynamics and potential determinants of breeding success in a populatio...

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Published in:Ostrich Vol. 96; no. 1; pp. 42 - 53
Main Authors: Porter, Roger N, Howells, William W, Weiersbye, Ingrid B, Hoffman, Ben, Porter, Sean N
Format: Journal Article
Language:English
Published: Johannesburg Taylor & Francis 02.01.2025
Taylor & Francis Ltd
Subjects:
Animal breeding
anthropogenic pressures
Aquatic reptiles
Biodiversity
birds of prey
Breeding seasons
Breeding success
Conservation
Crocodiles
Crocodylus niloticus
Density
Environmental changes
Farms
Flight
Food
Food resources
Food sources
global change
Habitats
Human influences
intraspecific competition
Juveniles
land cover
land use change
landcover
Landscape
landscapes
migratory behavior
Migratory birds
Milvus
Milvus aegyptius
nest density
Nesting
Nests
ostriches
Plant breeding
Population decline
population dynamics
Populations
raptor
Reproduction
South Africa
Success
summer
Threatened species
Woodlands
South Africa
KwaZulu-Natal Province South Africa
ISSN:0030-6525, 1727-947X, 1727-947X
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Summary:Anthropogenic habitat transformation is one of the leading causes of biodiversity decline. Migratory birds, particularly many raptor species, are increasingly threatened by global environmental change. We investigated the nesting dynamics and potential determinants of breeding success in a population of the Yellow-billed Kite Milvus aegyptius across a human-modified landscape in an area of KwaZulu-Natal Province, South Africa. We monitored Yellow-billed Kite nests in a 17-km 2 study area every ∼3 days throughout the 2016-2017, 2017-2018 and 2018-2019 austral spring- summer during the breeding season. The average (±SD) nest density was 3.3 ± 0.4 nests per km 2 . Nearest-neighbour nest distance increased significantly with increasing distance to the nearest regular food source, a Nile crocodile Crocodylus niloticus farm. Cultivated and open woodland landcover were consistently avoided for nesting, while riparian landcover was preferred. Nest build day and intraspecific pressure were significantly negatively related to success in raising a free-flying juvenile, while the distance to the nearest crocodile farm and landcover type were not. Free-flying juveniles per nest ranged from 0 to 3, with an average (±SE) of 1.31 ± 0.02 juveniles per nest. The number of free-flying juveniles raised was significantly negatively related to intraspecific pressure but not to nest build day, distance to the crocodile farm or landcover type. The conservation implications of our findings are relevant to other breeding Yellow-billed Kite populations likely experiencing similar anthropogenic pressures. The availability of suitable nesting habitat, especially riparian areas characterised by dense vegetation and tall trees, is critical for maintaining the population in human-modified landscapes subjected to land transformation. Although surplus and consistent food did not influence breeding success, sufficient food resources may mitigate population decline in areas prone to land transformation by influencing an increase in nest density, until intraspecific pressure exceeds a threshold.
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ISSN:0030-6525
1727-947X
1727-947X
DOI:10.2989/00306525.2025.2480667