Nest searching and mapping of breeding pairs
Collecting data on nesting waterfowls involves potential disturbance to
nesting birds, whether direct (handling eggs) or indirect (walking near
birds on nests) as reported by Austin & Buhl (2008). Grey Crowned Crane
nests are described as difficult to locate from the ground (Morrison &
Bothma, 1998). With these considerations, nests were not actively
searched as this would have likely resulted to trampling on vegetation
in the breeding habitats, cause disturbance to nesting waterfowls and
expose clutches and chicks to egg poachers who frequent the breeding
sites– nests were thus visited once. Location of nests was discerned
from cues of a nesting pair behaviour (e.g. when an individual was
observed going for a nest relief), and from information obtained from
volunteer fishermen and herdsmen. Binoculars and telescopes were
additionally used to scan marshes for incubating cranes.
A pair was considered as occupying a breeding territory if i) was
frequent within a specific section of the lake or man-made wetland; ii)
was known to have bred in the site in the past, iii) was observed
gathering nesting material and building a nest, iv) the male
aggressively confronted conspecific males, often involving a brief fight
and chase, and v) a pair was observed driving out a juvenile (as a sign
of re-nesting). Mapping of breeding pairs was restricted to one week in
December 2018, the peak of the breeding season in a normal local weather
pattern, and repeated two weeks later to confirm positions of breeding
pairs as being territorial. Newly appearing pairs afterwards and showing
territorial behaviour were not considered (Bradter, Gombobaatar,
Uuganbayar, Grazia, & Exo, 2005).Flocks did not account for territorial
breeding pairs and were often found in fields at some distance from the
lake. In this study, breeding season was considered as the period
between lying of the first clutch and the time when the last chick
fledged, this period approximately lasting 13 months for the current
study from early-April2018 to mid-April 2019.