Forest structure influences the abundance of Araneus lathyrinus (Araneae, Araneidae), an important avian prey item during nestling rearing

Abstract

Habitat alteration reduces the biomass and diversity of arthropods, the main food resource of many birds. We study the relationship between the forest structure and composition and the abundance of the orb weber Araneus lathyrinus, a high-quality prey item frequently delivered to nestlings during the rearing period. We conducted counts of spiders in a forested area of central-eastern Argentina which has been fragmented by land use in recent decades. We sampled a total of 288 trees and counted 1736 specimens. The abundance of spiders was lower in isolated patches (a product of the land use in recent decades) than in continuous forest and was lower in plots with higher proportions of exotic trees. In addition, abundance varied among the three tree species sampled (Celtis tala > Scutia buxifolia > Gleditsia triacanthos), with lowest abundance in the exotic tree. In the worrisome global context of habitat loss, our results highlight the importance of preserving forest areas with interconnected patches and high proportions of native trees. Accordingly, we recommend that management actions focus on the preservation of forested areas with these characteristics to ensure the availability of this key food resource for birds.