(1) Feeding rate and meal size of Leach's storm-petrel at Kent Island, New Brunswick, were studied by analysing mass increments of the chicks. (2) Meal size, estimated by mass increments over short periods during the night, averaged 10.0 g (S.D. = 2.3 g, range approximately 5-13 g). (3) Mass increments over 24 h (NET) were linearly related to the sum of positive mass increments over 3-h intervals during the night (SUM) by the equation NET = -6.04 + 0.92 SUM (r2 = 0.88). With knowledge of meal size and of this relationship, we estimated the number of feeds per night (0, 1, or 2) from NET. (4) During August in both 1962 and 1983, each parent fed its chick on 43% of nights. Each parent fed independently of the other. Percentages of nights with 0, 1, and 2 feeds were 35, 44, and 21%, which do not differ significantly from the binomial probability function with P = 0.43. (5) The probability of a parent feeding its chick (p) did not vary with respect to date (i) in 1983. In 1962, P, was significantly below average on 3 nights and above average on 3 nights. Periods between feeds by either or both parents were 57% = 1 day, 31% = 2 days, and 11% = 3 days in 1983, and 45%, 43%, 9%, 2% (4 days), and 1% (5 days) in 1962. (6) We estimated that intervals between feedings by an individual parent were 22% = 1 day, 38% = 2 days, 23% = 3 days, and 17% = 4 days in 1983. Meal size was independent of the number of days since the previous feeding. (7) After removing variation attributable to date in season (hence age) and difference between chicks, variance in chick mass was 47.8 g2. This was approximately equal to the variance in NET (51.6 g2), indicating that short-term variance in chick mass is generated anew each night by variation in amount fed. Furthermore, the covariance between NET on one night and the next is negative and about half the value of the variance, demonstrating short-term regulation of food delivery. (8) Variability in feeding rate and meal size indicates that intervals between feeds rarely are so long as the period over which chicks could survive utilizing only their substantial fat reserves. This calls into question the prevalent idea that the purpose of the fat deposits is to guarantee survival through periodic fasts resulting from unpredictable food supplies or feeding conditions. Furthermore, food provisioning in storm-petrels appears to be regulated by the requirements of the chicks, rather than by variation in food resources available to adults.