Breeding pair abundances derived from nestbox studies of the Netherlands Institute of Ecology (NIOO-KNAW)

Method steps

1. At each study site, nest boxes were checked at least once a week. Breeding parameters (such as laying date, clutch type and clutch size) were recorded and adults were captured in the nest box. Adults were identified based on their ring number and newly ringed if they do not have a ring yet.
2. These data were transformed into the SPI-Birds standard format (version 1.1; https://github.com/SPI-Birds/documentation/blob/master/standard_protocol/SPI_Birds_Protocol_v1.1.0.pdf) using a tailor-made pipeline (https://github.com/SPI-Birds/pipelines/blob/master/R/format_NIOO.R).
3. From the data in the SPI-Birds format, the number of breeding pairs per year, location and species was calculated. This was done by counting the number of first clutches. First clutches refer to the first clutch laid by a female in that season and are defined based on strict decision rules (see page 16 in SPI-Birds Standard Protocol, version 1.1; https://github.com/SPI-Birds/documentation/blob/master/standard_protocol/SPI_Birds_Protocol_v1.1.0.pdf).

1. Cyanistes caeruleus
   common name: Blue tit rank: species
2. Ficedula hypoleuca
   common name: Pied flycatcher rank: species
3. Parus major
   common name: Great tit rank: species
4. Periparus ater
   common name: Coal tit rank: species
5. Poecile palustris
   common name: Marsh tit rank: species
6. Sitta europaea
   common name: Eurasian nuthatch rank: species
7. Phoenicurus phoenicurus
   common name: Common redstart rank: species
8. Passer montanus
   common name: Eurasian tree sparrow rank: species