The chemical characteristics of the surface soils affected by Sooty Shearwaters were investigated by analysis of 10 core samples taken from within each of three types of quadrats in three sampling areas on Motuara Island, South Island, New Zealand. These were (a) areas within 50cm of burrow entrances, but where leaf fall and trampling by the birds had been excluded (BURROW QUADRATS), (b) areas away from burrows and with normal leaf fall and plant cover present (LEAF LITTER PRESENT QUADRATS) and (c) areas similar to Leaf Litter Present Quadrats, but where all litter and plants had been removed at the beginning of the study (3 July, 1990) in cool, damp, calm conditions (LEAF LITTER ABSENT QUADRATS). Statistically significant differences were found between Burrow and other Quadrats, the former soil having lower pH values but higher electrical conductivity (EC) and phosphate levels. This suggests that the guano of Sooty Shearwaters lowers soil pH through the nitrification from ammonium to nitrate after mineralization of organic nitrogen, and enhances the EC and phosphate content in the surface layers. On the other hand, there was no significant difference in soil pH, EC, phosphate, potassium and total carbon and nitrogen content between Leaf Litter Present Quadrats and Leaf Litter Absent Quadrats, indicating that the absence of leaf litter and plants for a short period in winter does not significantly effect the chemical characteristics of the surface soils on Motuara Island.