Data from: Occupancy patterns and upper range limits of lowland Bornean birds along an elevational gradient

Aim: The traditional view of species' distributions is that they are less abundant near the edges of their ranges and more abundant toward the center. Testing this pattern is difficult because of the complexity of distributions across wide geographical areas. An alternative strategy, however, is to measure species' distributional patterns along elevational gradients. We applied this strategy to examine whether lowland forest birds are indeed less common near their upper range limits on a Bornean mountain, and tested co-occurrence patterns among species for potential causes of attenuation, including signatures of habitat selection and competition at the periphery of their ranges. Location: Mt. Mulu, Borneo Taxon: Rain forest birds Methods: We surveyed lowland forest birds on Mt. Mulu (2,376 m), classified their elevation-occupancy distributions using Huisman – Olff – Fresco (HOF) models, and examined co-occurrence patterns of species pairs for signatures of shared habitat patches and interspecific competition. Results: For 39 of 50 common species, occupancy was highest at sea level then gradually declined near their upper range edges, in keeping with a 'rare periphery' hypothesis. With respect to habitat selection, lowland species do not appear to cluster together at sites of patchy similar habitat near their upper range limits; neither are most lowland species segregated from potential montane competitors where ranges overlap. Main conclusions: High relative abundance at sea level implies that species inhabit 'truncated niches' and are not currently near the limits of their fundamental niche, unless unknown critical response thresholds exist. However, indirect effects of increasing temperature predicted under climate change scenarios could still influence lower range limits of lowland species indirectly by altering habitat, precipitation regimes, and competitive interactions. The lack of non-random co-occurrence patterns implies that patchy habitat and simple pairwise species interactions are unlikely to be responsible for upper range limits in most species; diffuse competition across diverse rain forest bird communities could still play a role.Presence/absence of bird species on Mt. Mulu Presence/absence (1/0) records of lowland and montane bird species on Mt. Mulu in Borneo. Only species detected at >=10 point count locations are included. Rows are species scientific names, and columns are point count location names on Mt. Mulu. Point count lat, lon (WGS 84), and elevation (m) are available in a separate file. These data were used to plot HOF curves (for the lowland species), and to test for significantly co-occurring pairs. Mulu_birdspecies_presence.txt Point count location information This gives latitude and longitude (WGS 84) and elevation (m) information about point count locations for which species are listed in the previous file. All from Mt. Mulu, Sarawak, Borneo. Files are linked by the point names field (rows in this column). 'Unkn' values for lat lon are unknown because GPS wasn't working those days, but near other points at a given elevation. point_information_Mulu.txt Funding provided by: National Science FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: DEB-1241059See articl