DOI: 10.5061/dryad.677b1c7
title: Data from: Occupancy patterns and upper range limits of lowland Bornean birds along an elevational gradient

description: 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.
description: 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 &gt;=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
description: See article