1. Avian Sleep Group, Max Planck Institute for Ornithology, Seewiesen 82319, Germany.
2. Department of Behavioral Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Seewiesen 82319, Germany.
3. Institute of Neuroinformatics, University of Zurich/Eidgenössische Technische Hochschule Zurich, Zurich 8092, Switzerland.
4. e-obs GmbH, Gruenwald 82031, Germany.