Water Pipit (Anthus spinoletta) Science Article 3
abstract
Insufficient food provisioning by parents can reduce growth rate of altricial nestlings, their size and weight at fledging, and also affect survival. Therefore at low food availability, parents should increase their food provisioning effort. In insectivorous Water Pipits Anthus spinoletta prey biomass differed up to 50 times among home ranges; nevertheless, number, size and weight of fledglings did not differ between home ranges with low and high prey biomass. Based on predictions from the literature, we investigated whether and how parents adjust their provisioning behaviour to food availability, measured by arthropod biomass, and to nestling demands, measured by brood size, nestling age and ambient temperature. Foraging distances did not vary significantly with any of the four variables. Feeding rates were also not related to food availability, but increased with brood size in both sexes. In addition, females showed a tendency to increase feeding rate with decreasing air temperature. Our results suggest that, at least in some years, arthropod food is so abundant in the birds’ environment that it does not limit reproductive success
Rauter C.M., Brodmann P.A. & Reyer H.U., ARDEA 88 (1): 81-90