Pied flycatcher: climate change and breeding behaviour

The breeding behaviour of the pied flycatcher has been disrupted by climate change.

Trends in laying date

The warmer Dutch springs are causing trees to come into leaf earlier and insect populations to peak sooner. As the pied flycatcher overwinters in West Africa and is not returning to the Netherlands earlier, there is a risk that its growing chicks will be out of sync with the insect peaks. The females are attempting to compensate, by breeding sooner after arrival in the Netherlands: the mean laying date of the pied flycatcher is now 8.5 days earlier (see left-hand graph). This earlier activity puts more stress on the females, because they have less time to recover from the long haul from Africa. In addition, the insect peaks are missed more often.

Trends in numbers

The disruption of breeding behaviour could have caused this species to decline, but since 1990 the numbers of pied flycatcher in the Netherlands have remained stable. There are regional differences, however (see right-hand graph): in the north of the country the species increased for several years, but has been declining significantly since 1998. In the south the species has been declining significantly since 1990. It has been suggested (Boele et al. 2001) that these trends are associated with the lower mean temperatures in the north, which cause trees to come into leaf later and insects to peak later. Birds returning from Africa find more insects in the north of the country later in the season than they do in the south. Both (2002), however, has questioned this interpretation of the regional trends.

Technical note

The laying date is expressed as the day number (day 1 = 1 January, and so on). The laying date is the average of the earliest 25% of all clutches found. The spring temperature is the average of the daily means for February through June, as recorded at the met station at De Bilt.

The boundary between north and south Netherlands is at the latitude of Amersfoort.

The data are from the Ecological Monitoring Network's nest-mapping project and the national network for monitoring breeding birds. The index numbers refer to the number of breeding pairs.

References

• Boele, A., A.J. van Dijk, F. Hustings en D. Zoetebier (2001). Regionale verschillen in aantalsontwikkeling van de Bonte Vliegenvanger Ficedula hypoleuca. Limosa, 74 (3): 103-115.
• Both, C. en M. Visser (2001). Adjustment to climate change is constrained by arrival date in a long-distance migrant bird. Nature, 411: 296-298.
• Both, C. (2002). Nemen bonte vliegenvangers Ficedula hypoleuca af door klimaatsverandering? Limosa, 75 (2): 73-78.
• Majoor, F., R. Foppen, F. Willems en D. Zoetebier (2001). De waarde van het nestkaartenproject voor signalering en beleid. Intern Rapport SOVON. Beek-Ubbergen.