Diurnal Forest Thrush abundance positively covaries with both prey availability and small Indian mongoose abundance

Abstract

Ground-dwelling omnivorous bird species living on tropical islands are particularly vulnerable to deforestation, introduced mammal predators, and declining insect populations. However, little is known about the relative influences of predation risk and invertebrate prey availability on the spatial distribution and abundance of such species in forested habitats. We investigated spatial variation in the diurnal abundance of the near-threatened Forest Thrush (FT), Turdus lherminieri, a Caribbean-endemic and secretive ground-dwelling species, in March 2020, corresponding to the dry season, in Guadeloupe, French West Indies. We used camera traps to assess spatial variation in the abundance of FT and that of potential diurnal mammalian predators among three forest types: tropical rainforest (TRF), tropical swamp forest (TSF), and tropical dry forest (TDF). We characterized sampling sites according to temperature, canopy openness, leaf-litter biomass, and estimated local invertebrate abundance and biomass. FT were relatively common, being detected at 21 (35%) of 60 camera-trap locations during the study. FT abundance was significantly higher in TRF compared to the other two habitats, and covaried positively with both invertebrate biomass and the abundance of the small Indian mongoose, Urva auropunctata. We discuss our results in relation to previous studies on habitat selection by tropical insectivore, ground-dwelling bird species, and address their overall relevance for FT conservation in the insular Caribbean.