Egg covering in great tits and effects on pied flycatchers

This dataset contains data from experiments carried out in a woodland area
and described in the paper: “T. Slagsvold, and Wiebe, K. L. (2021) “Egg
covering in cavity nesting birds may prevent nest usurpation by other
species.” https://doi.org/10.1007/s00265-021-03045-w The
experiments investigated a new hypothesis, namely that the cavity nesting
birds, like titmice, cover their eggs when they leave the nest during the
egg laying period to prevent usurpation of the cavity by other
birds. We provided nest boxes in a woodland area
and filmed great tit (Parus major)nests during the egg-laying
period to study the behavior of the female. Then we presented prospecting
male pied flycatchers (Ficedula hypoleuca) with a dyad of nest
boxes, to study whether they hesitated to enter a box when the tit eggs
were covered or not, depending on the size and depth of the box. Main
results of the experiments were that (1) during the egg-laying
period, the female great tit spent bouts of highly variable length outside
the nest box, from a few minutes to more than an hour. Therefore, when
visiting a nest cavity, prospecting birds would have difficulty predicting
whether an aggressive tit owner would soon return. (2) The pied
flycatchers hesitated longer to enter a nest box with no visible tit eggs
than a box with exposed eggs. (3) This was most evident for nest boxes
with dark versus light interior paint, supporting the idea that
better interior illumination makes prospecting birds more confident about
entering an unfamiliar cavity.