Long-term population monitoring has become an important tool for conservation management and indicator of environmental change. In many species nest counts are used as an index of population numbers. A pilot study using double-counts in Fiordland crested penguins (Eudyptes pachyrhynchus) found that up to 12% of nests had failed following the first count, raising concerns about search-related disturbance effects and the reliability of long-term monitoring data.
The New Zealand Garden Bird Survey started in 2007 primarily to monitor long-term trends in common garden bird populations. The method was based on the Big Garden Birdwatch in the UK. Volunteers spent one hour in midwinter each year recording for each bird species the largest number of individuals detected at any one time in their gardens, as an index of abundance. A large number of species was recorded, the two most numerous being house sparrow (Passer domesticus) and silvereye (Zosterops lateralis).