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The breeding biology of the Paradise Shelduck (Tadorna variegata) was studied on hill-country farmland west of Tokomaru Bay, New Zealand, during 1973-1976. Throughout the breeding season the shelduck population comprised territorial pairs, which occupied areas of pasture surrounding stock ponds or other water bodies, and flocks, which were mostly of juveniles and which remained at specific sites on river terraces or hillsides. Breeding was attempted only by the territorial pairs. Prospecting for nest sites started in late June and 62% of 47 nests found were in hollow logs on the ground’. Laying began in August and the mean size of 36 clutches was 9.4. Of 282 eggs, 5% were infertile and 87% of the fertile eggs hatched. Only 20% of the pairs which lost their clutches re-nested. Ducklings were reared on stock ponds, in streams or rivers, and in swampy soaks on hillsides. About 60% of the ducklings reaching the rearing areas survived the 8-week fledging period. The main causes of duckling mortality were bad weather and predation by feral cats. During their first week, ducklings fed mostly on aquatic insects, and thereafter on plant material. Of 67 ducklings which fledged, 54.7% were males, and, after fledging, males dispersed more widely than females.