Data from: Northern flickers only work when they have to: how individual traits, population size and landscape disturbances affect excavation rates of an ecosystem engineer

Woodpeckers are considered ecosystem engineers because they excavate tree
cavities which are used subsequently by many species of secondary cavity
nesters for breeding. Woodpeckers have the choice of excavating a new hole
or reusing an existing one, and this propensity to excavate (e) may affect
community dynamics but has rarely been investigated. Using 18 years of
data on a population of northern flickers Colaptes auratus, I tested six
hypotheses to explain the propensity to excavate (e) in a landscape which
experienced two types of disturbance: pine beetles and wildfires.
Woodpecker age, breeding experience and mate retention had little
influence on e which varied between 13-39% annually and averaged 23% for
1843 first nests over the 18 years. Body size and body condition of males
and females were not associated with e but rates of excavation declined
seasonally, suggesting time rather than energy costs limited excavation
effort. Reduced cavity availability mediated through high conspecific
density coupled with wildfires triggered relatively high excavation rates,
up to 39% but e decreased to baseline levels three years after the
landscape disturbances. Nearly 2/3 of males did not excavate in their
lifetime but apparently, e is great enough to balance the average rate of
cavity tree loss in this forest which is 11% annually. Excavation
propensity in flickers is flexible, but the birds reduce their work levels
if there is a surplus of holes available.