Data from: Connectivity with primary forest determines the value of secondary tropical forests for bird conservation

Predicted species extinctions caused by the destruction and degradation of
tropical primary forest may be at least partially mitigated by the
expansion of regenerating secondary forest. However, the conservation
value of secondary forest remains controversial, and potentially
underestimated, since most previous studies have focused on young,
single-aged, or isolated stands. Here we use point count surveys to
compare tropical forest bird communities in 20–120-yr-old secondary forest
and primary forest stands in central Panama, with varying connectivity
between secondary forest sites and extensive primary forest. We found that
species richness and other metrics of ecological diversity, as well as the
combined population density of all birds, reached a peak in younger
(20-yr-old) secondary forests, and appeared to decline in older secondary
forest stands. This counter-intuitive result can be explained by the
greater connectivity between younger secondary forests and extensive
primary forests at our study site, compared with older secondary forests
that are either (1) more isolated, or (2) connected to primary forests
that are themselves small and isolated. Our results suggest that
connectivity with extensive primary forest is a more important determinant
of avian species richness and community structure than forest age, and
highlight the vital contribution secondary forests can make in conserving
tropical bird diversity, so long as extensive primary habitats are
adjacent and spatially connected.