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.