Seasonal patterns in the productivity of Meadow Pipits in the uplands of Scotland

Abstract

In many birds, it is assumed that conditions for breeding follow a seasonal pattern of improvement and then decline and that for each individual in the population the optimal clutch size is larger when conditions for breeding are more favorable. While this is assumed to be the case for single-brooded species, the situation is more complex for multi-brooded species, which start breeding before the date when their optimal clutch size is greatest and conditions are best for raising nestlings. The seasonal patterns of productivity for multi-brooded species are not generally understood. We compared the clutch size, egg size and weight, and the nesting success of Meadow Pipits (Anthus pratensis) nesting during the early and late stages of the breeding season in Scotland. We also compared the provisioning rates, diet, and number of prey items fed to nestlings. Eggs laid late in the season were significantly larger and heavier than eggs laid earlier in the season. There were generally no differences in diet or provisioning rates of nestlings throughout the season. Despite producing larger eggs late in the season, the probability of such an egg producing a nestling that successfully fledged was 17% lower than an egg laid early in the season. This was mainly due to a significant increase in nest predation late in the season.