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Summary.  The relation between a population of Starlings and its food supply during the breeding season was investigated at Craibstone, near Aberdeen, during 1950, 1951 and 1952.  In a square mile, including Craibstone, the number of breeding females increased from 43 in 1950 to 52–54 in 1951, and to 78 in 1952.  During the breeding season the Starlings obtained most of their food in the upper layer of the soil in pasture fields. Leatherjackets (Tipula sp. larvae) were the most important, and the seasonal variation in their biomass was measured. The period of availability is long, but that of great biomass is short. Earthworms were abundant in the soil, but formed a small proportion of the food taken.  Synchrony of laying the first clutches is marked; in second clutches (common at Craibstone in each year) it is less pronounced and is derived from that of the earlier layin.  Starlings fed from a limited number of feeding areas.  The food brought to the nestlings was studied in part by high‐speed Hash photography.  On the average leatherjackets formed over 80% of the food brought to the nestlings and earthworms 16%.  The weight of, and variation in, individual feeds were calculated.  There is a marked peak of feeding activity in the early morning, often with a lesser peak in the afternoon. Earthworms tend to be brought early in the morning.  The proportions of different items do not vary seasonally.  The relation between feeding rate and the amount of food brought is not constant.  Owing to individual differences in the feeding activity of parents and the response of the young, the amount of food required to rear a brood cannot be estimated.  The proportion of available leatherjackets consumed by nestlings was about 1·9% in 1951 and 7% in 1952.  The mean clutch‐size was similar in each year, and second clutches were smaller than first.  Nestling weights did not differ significantly between broods of different sizes or in relation to the amount of food available.  It was concluded that:  The synchrony of first clutches may be due to the advantage of having successful second broods, and the evidence suggests that these are ultimately controlled by the date the leatherjackets emerge. The synchrony may also have survival value in providing the opportunity for gregarious feeding by the adults and, later, the juveniles.  The occurrence of second broods appears to be determined by how early breeding starts and when the leather‐jackets disappear from the soil.  Breeding‐rate and success were not closely related to the available food supply.  There is much evidence to suggest that the available food‐supply is the ultimate factor timing the end of the breeding season, but it probably does not determine the onset of breeding.  The density of the breeding population is not controlled by the food available during the breeding season.

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