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).