Foraging site choice and diet selection of Meadow Pipits Anthus pratensis breeding on grazed salt marshes

Auteurs: van Klink Roel, Mandema Freek S., Bakker Jan P., Tinbergen Joost M.
Bron: Bird Study; Mar 2014, Vol. 61 Issue 1, p101-110, 10p
Abstract: 

Capsule Breeding Meadow Pipits foraged for caterpillars and large spiders in vegetation that was less heterogeneous than vegetation at random locations.

Aims To gain a better understanding of the foraging ecology of breeding Meadow Pipits on grazed coastal salt marshes, we tested three hypotheses: (1) there is a positive relation between vegetation height and prey abundance, (2) adult birds preferentially forage at locations with great heterogeneity in vegetation height, thereby maximizing both food abundance and accessibility, and (3) adult birds forage selectively for specific prey items.
Methods We measured food availability in relation to vegetation structure, habitat use and nestling diet for six individual nests. Nestling diet was determined by microscopic analysis of faeces while food availability over different vegetation heights was estimated by suction sampling. Information on habitat use was gathered by direct observation. Foraging locations were compared to random locations at the same distance from the nest.
Results Nestling diet mainly consisted of larger spiders (> 5 mm) (38% of prey individuals), caterpillars (c. 2 cm) (38%), other insect larvae (12%) and flies and wasps (7%). There was a positive relationship between vegetation height and prey availability. Contrary to predictions, vegetation at Pipit foraging locations was less heterogeneous than at random locations, yet we found no evidence for a preference for short or tall vegetation. We found strong evidence for selective foraging for larger prey, since the relative abundance of especially large spiders and caterpillars was much higher in the faecal samples than in the field. This diet differed considerably from Meadow Pipit diet reported from other habitats.

Conclusion These findings suggest that the creation of heterogeneity in vegetation height by grazing or otherwise may not be invariably beneficial to breeding Meadow Pipits.