Data from: Network structure of avian mixed-species flocks decays with elevation and latitude across the Andes

Birds in mixed-species flocks benefit from greater foraging efficiency and
reduced predation but also face costs related to competition and activity
matching. Because this cost-benefit trade-off is context-dependent (e.g.,
abiotic conditions, habitat quality), the structure of flocks is expected
to vary along elevational, latitudinal, and disturbance gradients.
Specifically, we predicted that the connectivity and cohesion of flocking
networks would (1) decline towards tropical latitudes and lower
elevations, where competition and activity matching costs are higher, and
(2) increase with lower forest cover and greater human disturbance. We
analysed the structure of 84 flock networks across the Andes and assessed
the effect of elevation, latitude, forest cover and human disturbance on
network characteristics. We found that Andean flocks are overall
open-membership systems (unstructured), though the extent of network
structure varied across gradients. Elevation was the main predictor of
structure, with more connected and less modular flocks upslope. As
expected, flocks in areas with higher forest cover were less cohesive,
with better-defined flock subtypes. Flocks also varied across latitude and
disturbance gradients as predicted, but effect sizes were small. Our
findings indicate that the unstructured nature of Andean flocks might
arise as a strategy to cope with harsh environmental conditions.