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Egg covering in great tits and effects on pied flycatchers

Cite this dataset

Slagsvold, Tore; Wiebe, Karen L. (2021). Egg covering in great tits and effects on pied flycatchers [Dataset]. Dryad.


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.”

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.


The dataset was collected using extensive video filming of nest boxes provided in woodland areas near Oslo, as part of a project on cavity nesting birds at Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Norway, and at Department of Biology, University of Saskatchewan, Saskatoon, Canada.

Usage notes

The readme file contains an explanation of each of the variables in the dataset, and its measurement units. Information on how the measurements were done can be found in the associated paper referenced above. 


Natural Sciences and Engineering Research Council, Award: 203177