Data from: Floaters may buffer the extinction risk of small populations: an empirical assessment

The high extinction risk of small populations is commonly explained by
reductions in fecundity and breeder survival associated with demographic
and environmental stochasticity. However, ecological theory suggests that
population extinctions may also arise from reductions in the number of
floaters able to replace the lost breeders. This can be particularly
plausible under harsh fragmentation scenarios, where species must survive
as small populations subjected to severe effects of stochasticity. Using a
woodpecker study in fragmented habitats (2004–2016), we provide here
empirical support for the largely neglected hypothesis that floaters
buffer population extirpation risks. After controlling for population
size, patch size and the intrinsic quality of habitat, populations in
patches with floaters had a lower extinction probability than populations
in patches without floaters (0.013 versus 0.131). Floaters, which often
replace the lost breeders, were less likely to occur in small and
low-quality patches, showing that population extirpations may arise from
unnoticed reductions in floater numbers in poor-quality habitats. We argue
that adequate pools of the typically overlooked floaters may buffer
extirpation risks by reducing the detrimental impacts of demographic and
environmental stochasticity. However, unravelling the influence of
floaters in buffering stochastic effects and promoting population
stability require additional studies in an ample array of species and
stochastic scenarios.