FOOD SHORTAGE IN SMALL FRAGMENTS: EVIDENCE FROM AN AREA-SENSITIVE PASSERINE

Abstract

Many forest-interior songbirds are considered “area sensitive” because they are absent from smaller forest remnants in fragmented landscapes. Reductions in food abundance with fragment size could explain area sensitivity, but to date, only one empirical study has investigated this possibility. From 1995 to 1997, we tested the food abundance hypothesis in two small (∼55-ha) and two large (>400-ha) forest fragments located in a matrix of agricultural land in northeastern New South Wales, Australia. We measured differences in food abundance by comparing the biomass of surface-dwelling invertebrates in large and small fragments. We also determined whether food supply was associated with foraging efficiency and reproductive performance in an area-sensitive, ground-foraging insectivore, the Eastern Yellow Robin (Eopsaltria australis), breeding at these same sites. Invertebrate biomass in the small fragments was about half of that in the large fragments. Incubating female robins received 40% less food from males...