The Effect of Drought on Duckling Survival of Maned Ducks

In: Wildlife Research, Band 16, Heft 4, S. 405

Abstract

Regular brood surveys on a population of maned ducks, Chenonetta jubata, in south-eastern Australia
provided information on the timing of breeding, brood sizes, duckling survival and production for this
species. Over three years (1981-83), most breeding was during the spring, ducklings hatching between
late August and late November. Some autumn (March-May) breeding also occurred. Timing of breeding
appeared to be more closely related to the abundance of food than to rainfall alone. There were clear
differences in reproductive success between the drought year of 1982 and the two years of similar
weather, 1981 and 1983. Breeding began later in 1982, with a mean hatch date of 18 � 5.1 November,
compared with 7 � 3.6 October in 1981 and 21 � 5.1 September in 1983. Broods hatched over 43 days
in 1982 compared with 69 days in 1981 and 101 days in 1983. Also, duckling survival was lowest in
1982, with about a 20% probability of survival to fledging compared with 89% in 1981 and 82% in
1983. Only six broods were found in 1982 compared with 33 in 1981 and 30 in 1983. An estimated
158 and 176 ducklings survived to fledging compared with seven in 1982. Brood sizes at hatching did
not show the same clear annual differences. In 1981 and 1983 there were seasonal differences in brood
size at hatching. Broods were smaller late in the season (4.1) compared with early (7.2) and mid-season
(7.2). Broods were also larger in 1983 (7.2) than in 1981 (5.4). Brood size at hatching in 1982 was 6.0.