Studies on the Purple Swamphen, Porphyrio porphyrio, in Victoria

Abstract

Details are presented of gonad parameters and reproductive status, body measurements, moult, and food taken by purple swamphens collected in the Gippsland Lakes area between July 1971 and July 1973. Information from other studies is also discussed. Plant material (76% estimated average volume) dominated gizzard contents, particularly when inorganic material (23%) was discounted, and animal remains (c. 1%) were found in only 51 of the 234 gizzards with food examined. Mostly semi-aquatic plants were eaten, predominantly from Gramineae (59%), Cyperaceae (17%) and Hydrocharitaceae (11%), and Phragrnites australzs was the main species identified. The proportion of roots, rhizomes and tubers in gizzards increased in autumn samples. Monthly variations in the grit content of gizzards were significant; males (which were larger than females) held more large-sized fragments than females, and there was a moderate negative correlation between hard seeds and grit. Ovarian follicles were generally largest between July and November and seminiferous tubule diameters in males increased from June and July to reach a maximum from September to November; sperm were present from July to November. There were no simple correlations between gonad parameters and local rainfall in the preceding 30 days. The presence of a bursa of Fabricius did not successfully exclude reproductively active birds, but male swamphens with cloaca1 papillae and no bursa had larger testes than those with a bursa but no papillae. Colour scores for bill and tarsus showed some seasonal variation in subsamples of males and females. Management of wetlands for this species must take account of its requirement for a relatively restricted range of food types.