SUMMARYMONTAGUE, T.L., CULLEN, J.M. and FITZHERBERT, K. 1986. The diet of the Short-tailed ShearwaterPuffinus tenuirostrisduring its breeding season. Emu 86: 207–213.The diet of the Short-tailed ShearwaterPuffinus tenuirostriswas studied over two breeding seasons. Of 307 food samples collected, 74% contained fish, 56% crustaceans, and 13% cephalopods. Birds ate at least seven species of euphausiids, seven species of fish and two species of cephalopods. Most commonly encountered prey wereNyctiphanes australis, a euphausiid; andParaprone clausi, a pelagic amphipod. In both years the diet changed from a crustacean diet before egg-laying to a fish and crustacean diet after hatching. The change was attributed to a reduction in the surface swarming ofN. australisand an increase in the availability of post-larval fish, e.g. anchovy, after December. The mean weight of food that birds brought ashore increased from 19 g before egg-laying to 72 g during feeding of chicks. The mean weight of chick meals increased more than two-fold during January, then remained constant throughout the remainder of the season. Information of the distribution of one of the common prey species,N. australis, suggests that birds breeding at Phillip Island feed in Bass Strait and along the continental shelf.