INTRODUCTION
Knowledge of environmental features that determine habitat quality is critical to developing effective strategies for preserving and restoring natural areas that support species’ persistence and recovery (Hobbs, 2003). Nest-site selection is an integrative behavioural process that evolved to maximize reproductive success, adult and young survival. Therefore, understanding what key environmental variables influence nest-site selection in a species is the first step towards an effective management and conservation plan for a focal species or a group of birds such as cranes(Gruidae) (Hobbs, 2003;Swaisgood, Nordstrom, Schuetz, Boylan, Fournier & Shemai, 2017; van de Loock, 2019).
Nest-site selection starts with the breeding pair or individual choosing where to locate and build a nest. Animals such as fish, mammals, reptiles, birds, and invertebrates, must, therefore, choose very carefully where to put their nests for various reasons such as avoiding or reducing risks of predation (Holway, 1991; Götmark, Blomqvist, Johansson & Bergkvistv, 1995), increase offspring survival (Kolbe & Janzen, 2002) or in cavity-nesters, to maximise ambient illumination (Podkowa & Surmacki, 2017).Nest-sites are hence an important part of an animal’s niche (Gould, 2008), and a major determinant of reproductive success for many organisms since the quality of a nest-site is often linked to a species breeding success (Hatchwell, Russell, Fowlie & Ross, 1999). It is also a fundamental factor in the survival of a species through generations and is often a poorly understood component of many organisms’ reproductive investment (Baden, 2018). Parents must also consider cushioning themselves from predators and factors such as sunlight, wind and precipitation. Species also consider competition (for nesting space and resources such as food) from conspecifics and associates. The choice of a nest-site determines the available resources and threats that the animal and its offspring encounter, making it an important fitness-related decision (Tolvanen et. al. 2018).
While information on the breeding behaviour of most of the 15 extant species of cranes in the world today is available, it is cited as lacking for Grey Crowned Crane Balearica regulorum Bennett 1834(Figure 1). This crane is currently listed as Endangered on the IUCN Red List of Threatened Species as a result of rapid population declines arising from habitat loss and illegal removal of birds and eggs from the wild (BirdLife International 2020). Morrison (2015), describing it as an icon of Africa’s wetlands and grasslands where it is resident, has listed factors influencing breeding productivity as an essential knowledge gap that hinder effective implementation of its management and conservation actions across its African range. Further, this author describes this species as an icon of Africa’s wetlands and grasslands hence is a key species in the African landscape.
The purpose of this study was, therefore, to contribute to this knowledge gap. Specifically, investigated were the critical features influencing the probability of a nest-site (breeding habitat) selection of the Grey Crowned Crane population at Lake Ol’ Bolossat basin, a site holding its second-largest population in Kenya (Wamiti et al., 2019). Also determined were the number, distribution pattern and density of breeding pairs. These findings complement previous studies on the nesting behaviour of Grey Crowned Crane such as Pomeroy (1980a) and Morrison & Bothma (1998).