Black cormorant Phalacrocorax carbo (L., 1758) as a vector of fungi and parasites occurring in the gastrointestinal tract

The study reported in this manuscript is a part of extended investigations on transmission of fungi potentially pathogenic to man as well as parasitic flatworms and nematodes by wild fowl. The objective of this study was to identify the presence of fungi and parasites in the gastrointestinal tract of cormorants. Mycological and parasitological analyses were carried out on swabs taken from ontocenoses of beak, stomach, duodenum, jejunum, ileum and cloaca of 21 cormorants. The presence of fungi in the gastrointestinal tract was detected in 60% of the birds examined. They were isolated most frequently from beaks and cloacae of birds, duodenum was free of fungi. The most frequently isolated fungi were: Candida krusei and Debaryomyces hansenii. All isolates of fungi selected for enzymatic analyses were characterized by a high activity of esterases. Stomachs of all cormorants analyzed were found to contain Contracaecum rudolphii s.l. nematode. In turn, intestinal digesta of most of the birds were shown to contain Paradilepis scolecina tapeworm. Apart from tapeworms, duodenal digesta were also found to contain Paryphostomum radiatum digenea. The highest prevalence and intensity of infection with digenea was determined in the case of the birds shot in July.

Predation of Fish in Farm Dams by Cormorants, Phalacrocorax Spp.

The effect of cormorants on the survival of native warm-water fishes in farm dams in south-western New South Wales was monitored during 1979 and 1980. Three species of cormorants frequented the dams: the great cormorant Phalacrocorax carbo, the little pied cormorant P. melanoleucos, and the little black cormorant P. sulcirostris. In dams fished by cormorants, more than 50% ofthe fish were consumed unless abundant alternative prey, in this case crayfish Cherax destructor, was present. Dams stocked with few fish (approximately 150 ha-1) were less commonly fished than those stocked with many fish (more than 450 ha-1). The majority of dams in the study area were fished by cormorants, which were present from midwinter to midsummer in both years. The results, and an examination of aspects of cormorant biology and methods used to prevent birds eating fish at hatcheries, indicated that buffer populations of crustaceans and low fish stocking rates are suitable methods for minimizing predation of fish in farm dams by cormorants.

Waterbird Dynamics in the RIchmond VAlley, New SOuth Wales, 1974-77

'Monthly waterbird counts from February 1974 to June 1977 at six wetlands in the Richmond River valley in northern coastal New South Wales were analysed to investigate relationships between numbers of each species, and season and water variables. Black swan, Pacific black duck, purple swamphen, dusky moorhen, cattle egret, comb-crested jacana and sharp-tailed sandpiper were strongly influenced by season. Grey teal, straw-necked ibis, little black cormorant, Pacific heron and black-winged stilt numbers were related to Murray River discharge, an index of inland wetland availability in New South Wales, northern Victoria and parts of southern Queensland. Numbers of most waterbirds were highest on the coast from late summer to the end of winter. Their seasonal abundance patterns conform with the results of some previous studies but differ somewhat from others.

Ecology of the Little Black Cormorant, Phalacrocorax sulcirostris, and Little Pied Cormorant, P. melanoleucos, in Inland New South Wales II.* Proximate Control of Reproduction

Populations of P. sulcirostris and P, melano2eucos at a group of freshwater lakes were sampled approximately monthly between March 1972 and May 1975. Both species displayed strong gonadal cycles. In P, sulcirostris these were not regularly related to change in any one environmental component, though linear combination of a cyclic factor (temperature or daylength) with water level and food availability accounted for 85.2% of variation in the testis cycle. In a drought year significantly fewer males produced sperm, and the ratio of those producing much sperm to those producing little was significantly lower than in the two succeeding wet years. Eggs were laid in the wet years but not in the drought year, when there was no secluded, flooded timber in which to nest. In P. melanoleucos the date of onset of testis maturation was regular but that of regression was variable. Gonadal maturation was evidently initiated by increasing daylength and regression was initiated by low temperature, falling water level and perhaps lack of social stimulation. Eggs were laid in each year, but in the drought year not until the lakes refilled. Both major breeding seasons concluded abruptly with the widespread abandonment of eggs and young. In both species laying was completely synchronous within and slightly staggered between subunits of a colony, and very different between colonies.