A preliminary investigation of zooplankton diapausing eggs from waterbird faecal droppings in New Zealand

We analysed internal dispersal of zooplankton by waterbirds (endozoochory) in New Zealand, quantifying zooplankton eggs in faecal droppings collected at two lakes, Lake Rotoroa (Hamilton) and Lake Rotorua. Sixty-seven faecal droppings were collected from Mallard Ducks (20), Canada Geese (11), Greylag Geese (6), Black Swans (20) and Australian Coots (10). Fifty eggs were found, with a mean of 0.75 eggs per dropping, indicating that waterbirds consume zooplankton eggs, and that these pass through the digestive system. No significant difference was observed in the abundance of eggs among waterbird species, and no eggs hatched in the laboratory. Our results suggest that waterbird dispersal of zooplankton in New Zealand is occurring, but numbers being transported are low. Further, as non-native waterbirds such as mallard ducks and geese do not migrate in New Zealand to the extent they do elsewhere, they are likely not primary vectors for zooplankton dispersal.