DOI: 10.5061/dryad.83bk3j9zg
title: Dispersal limitation predicts the spatial and temporal filtering of tropical bird communities in isolated forest fragments

description: The link between dispersal traits and patterns of community assembly
 remains a frontier in understanding how vertebrate communities persist in
 fragmented landscapes. Using experimental release trials and intensive
 field surveys of bird communities in fragmented forests of the Peruvian
 and Colombian Andes, we demonstrate that morphological traits related to
 movement (1) predict experimental flight performance and (2) exhibit
 dispersal-mediated environmental filtering at the community scale. After
 correcting for body size, four traits hypothesized to influence flight
 ability (wing length, wing pointedness, wing loading, and eye size)
 predicted distance flown across a hostile experimental landscape, with
 successful species having significantly longer pointed wings, carrying
 less mass per unit wing area (i.e., lower wing loading), and having
 smaller eyes. Species with larger eyes also displayed increased flight
 latency, potentially due to disability glare. At the community scale we
 detected a gradient of dispersal-mediated environmental filtering in
 fragments compared to reference forest within the same landscape, with
 relative differences in trait values explained by the temporal and spatial
 extent of patch isolation. In the Colombian landscape where fragments had
 been isolated for &gt; 60 years, communities were filtered for species
 with long and narrow wings and small eyes, especially within the most
 spatially isolated fragments. We observed the opposite pattern in the more
 recently fragmented Peruvian landscape (15-30 years): communities within
 fragments tended to have shorter and more rounded wings compared to those
 in nearby contiguous forests, suggesting that dispersal-limited species
 accumulate in the initial years following patch isolation due to
 “restricted dispersal” and represent an extinction debt yet to be paid.
 Our results (1) experimentally validate the use of morphological traits as
 proxies for movement ability in fragmented landscapes, (2) demonstrate
 that visual acuity functions as a novel dimension of dispersal limitation,
 and (3) quantify how the spatial and temporal components of patch
 isolation produce a gradient in dispersal-mediated environmental filtering
 and extinction debt for communities inhabiting fragments.
description: The data consists of two sections. Users are asked to read the
 associated publication for details. 1. Behavioral data
 from experimental release trials conducted in the field in Peru on cloud
 forest bird species. Briefly, forest birds were captured with mist nets
 and released towards the forest across the pasture to assess interspecific
 variation in flight ability. Morphological predictors of flight
 performance (wing and eye dimensions) were based entirely on field
 measurements of birds in the hand. Processing: The attached data gives
 sample sizes and average species-specific values of flight performance
 metrics and morphological traits.  2. Community data
 from intensive field surveys of bird communities in the Andes of Peru and
 Colombia at sites located in contiguous mature forests and forest
 fragments. The Peru data were collected by the authors using point count
 and flock survey protocols (see Ausprey et al. 2022). The Colombia data
 were collected by Luis Miguel Renjifo using similar protocols (see Renjifo
 2001). The Peru morphological data (wings and eyes) were mostly derived
 from field measurements of birds in and supplemented with measurements of
 museum specimens. The Colombia morphological data were extracted from the
 AVONET database (Tobias et al. 2022) and a previously published paper on
 avian eye size variation (Ausprey 2021). Processing: The attached data
 gives site-specific community medians for wing and eye metrics. 
 Ausprey, I.
 J. 2021. Adaptations to light contribute to the ecological niches and
 evolution of the terrestrial avifauna. Proc. R. Soc.
 B.2882021085320210853.
 http://doi.org/10.1098/rspb.2021.0853. 
 Ausprey, I. J., F. L. Newell,
 and S. K. Robinson. 2022. Functional response traits and altered
 ecological niches drive the disassembly of cloud forest bird communities
 in tropical montane countrysides. Journal of Animal Ecology
 91:2314–2328. Renjifo, L. M. 2001. Effect of natural and
 anthropogenic landscape matrices on the abundance of Subandean bird
 species. Ecological Applications 11:14.
 Tobias et al. 2022. AVONET: morphological, ecological and
 geographical data for all birds. Ecology Letters
 25:581–597.
description: # Dispersal Limitation Predicts the Spatial and Temporal Filtering of
 Tropical Bird Communities in Isolated Forest Fragments
 [https://doi.org/10.5061/dryad.83bk3j9zg](https://doi.org/10.5061/dryad.83bk3j9zg) There are two spreadsheets. The first includes behavioral data from experimental release trials of cloud forest birds in Amazonas, Peru and associated traits. These are the same data presented in Table 1 of the manuscript. The second dataset includes site-specific median community trait values for bird communities in Peru and Colombia, as well as associated site data. Please see the metadata and original publication for details. Metadata for experimental release trials: | | | | --- | --- | | Success/Individuals | Number of individuals that successfully crossed the experimental landscape / Total number of individuals released | | Distance (m) | Mean distance flown (m) | | Delay (sec) | Mean delay (latency) in leaving the release box (seconds) | | Residual Wing Length | Residual wing length | | Hand-wing Index | Hand-wing Index | | Wing Loading | Wing Loading | | Residual Eye Size | Residual eyes size | | Mass (g) | Mass (g) | | | | | Please see the original publication for details on experiments and how morphological metrics were calculated. | Metadata for Communities: | | | | --- | --- | | ha | Fragment size in hectares | | distance.forest | Distance from fragment to nearest contiguous forest in meters | | matrix.prop | Proportion of 1000m buffer surrounding each Peru fragment composed of shrubs and forest | | matrix   | In Colombia some fragments were surrounded entirely by pasture and others partially by plantation forest | | hw | Handwing index | | wg.res | Residual wing length | | ey.res | Residual eye size | | | | | Values of "NA" refer to metrics related to fragments that are not applicable for forest sites |