Five-minute bird counts in New Zealand

The five-minute bird count (5MBC) method was developed in New Zealand in the early 1970s by the DSIR for monitoring forest birds. The method has been undertaken consistently for nearly 40 years leading to a large resource of counts (over 200 000). These counts are valuable as they often provide our only historical baseline measure of multi-species bird populations in New Zealand forests.Over 100 000 counts are held in the 5MBC database.The method was used between 1973 and 1992 by the DSIR, NZ Wildlife Service and NZ Forest Service to investigate important ecological questions such as which forests are important for which bird species, and whether pest control operations affect bird populations. The method played a role in persuading the government to cease all logging of native forests on public land in New Zealand in 2002. Reviewing 5MBC studies suggests a number of features of the method that should be considered when designing a study including that (1) it is an index not a census method, (2) observer, species behaviour, weather and season can all affect the number of birds detected, (3) counts are habitat- species- and probably year- specific preventing inter-species comparisons, and comparisons of species numbers at different sites if the counts were undertaken in different years. The method is suitable for investigating long term trends but there is likely to be considerable annual variability and a pilot study should be undertaken to investigate the number of counts needed to detect the difference of interest (i.e. power). The Department of Conservation website includes pages that provide resources for counters including standard data recording sheets. At present counters cannot enter their data into the 5MBC database and there is a risk that data from counts will continue to be lost.