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Water depth, vegetation height, and offshore distance are critical factors in nest-site selection for Grey Crowned Crane at Lake Ol' Bolossat, Kenya
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  • Wanyoike Wamiti,
  • Nathan Gichuki,
  • Dorcas Sigana,
  • Peter Njoroge,
  • Kerryn Morrison,
  • George Ndung'u,
  • Juan Rubalcaba
Wanyoike Wamiti
National Museums of Kenya
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Nathan Gichuki
University of Nairobi
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Dorcas Sigana
University of Nairobi
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Peter Njoroge
National Museums of Kenya
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Kerryn Morrison
Endangered Wildlife Trust
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George Ndung'u
Crane Conservation Volunteers
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Juan Rubalcaba
McGill University
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Abstract

Grey Crowned Crane Balearica regulorum is described as an icon of Africa’s wetlands and grasslands and is listed as Endangered on the IUCN Red List of Threatened species. Conservation efforts are partially hindered by lack of information on factors influencing breeding productivity, such as nest-site selection. Factors influencing nest-site selection were investigated at Lake Ol’ Bolossat, a 43.3 km2 wetland located in the central Kenya from 30 paired nests. Generalized Linear Mixed-Effects Models were used to analyse the relationship between factors influencing nest-site selection by cranes and variables that were predicted to have a compelling influence on nest-site selection besides i) food and nesting materials availability i.e. the offshore distance of the nest and water depth, and ii) nest concealment and susceptibility to predation i.e. vegetation height and grazing intensity. Results show that variables which had a significant influence on nest-site selection were: water depth (p=0.005), the offshore distance from the nest (p=0.037), and vegetation height (p=0.035). Cranes located their nests in water points above 50 cm deep, vegetation height of 60-90 cm, and preferably 100 m offshore. A minimum of 103 territorial pairs, both breeding and non-breeding cranes, were recorded. The middle section of the lake had the highest number (52), while north and south had 32 and 19 pairs respectively. The mean distance between any two pairs was 302.53±17.02 (SE) meters. This study sheds some light on the understanding of characteristics of Grey Crowned Crane’s nesting sites that will facilitate manipulation and management of breeding sites. Lake Ol’ Bolossat is consequently a critical breeding site with a substantial role in the species’ population recovery and survival. A wetland management option that aims at achieving sustainable use of lake’s resources by local communities without compromising needs of wildlife is highly commended.