Distributions of nocturnal birds on public conservation land
This measure relates to indicator 1.5.1 Species composition and diversity.
Background
Birds are a key indicator of environmental health. Traditionally, monitoring has involved field observers, but recently there has been an increased interest in the use of automatic recording devices (ARDs), which have the advantage of generating a reviewable permanent record and being able to record for extended periods of time. DOC has been using ARDs to record presence of nocturnal bird species since 2011/12 to improve our knowledge of their distributions.
Nocturnal ARD recordings detected a previously unknown population of Haast tokoeka.
What did we measure?
DOC has developed a national monitoring programme to assess the status and trends of biodiversity in approximately 1,400 sites that are evenly spaced across public conservation land (PCL). A random selection of approximately 280 of these sites are measured each year so that every site is measured once over a 5-year rotation cycle.
There are five bird count stations at each site spaced approximately 200 m apart. Observer counts are conducted during the day, while ARDs are set to record day and night and are processed manually to identify which species are present. This factsheet presents a selection of the results from nocturnal ARD recordings for the first 7 years of DOC’s monitoring programme (2011/12 to 2018/19), focussing on species that are nocturnal (e.g. kiwi, morepork) or that can be active day or night but are frequently heard calling at night (e.g. kākā, kea, long-tailed cuckoo).
What did we find?
- Thousands of 15-minute recording have been processed each year, revealing the presence of species of interest at many of the sites. In addition to the relatively commonly recorded species (Table 1), several rarely encountered species have been recorded, including Australasian bittern, marsh crake, New Zealand falcon, whio / blue duck and takahē (see Figure 1 - Maps).
- In 2015, the nocturnal ARD recordings detected a previously unknown population of Haast tokoeka in South Westland, approximately 15 km to the west of the nearest known population (see Figure 2 - Maps).
- Nocturnal records have greatly increased the presence information obtained from daytime field observations for some species – for example, kākā was recorded at 17.2% of sites based on 5-minute observer count data, but this increased to 35.4% of sites when nocturnal ARD data were added.
- The nocturnal ARD data were used in a research project investigating the optimal time of year and night to carry out surveys for morepork. The results suggested that, although there is local variation, the best timing for surveys was during spring and early summer in the first few hours after sunset. The results also indicated that the morepork detection probability varied across New Zealand PCL, being highest in Northland and lowest in the eastern South Island (see Figure 3 - Maps).
Figure 1: Distributions of nocturnal species based on automatic recording device (ARD) recordings.
Figure 2: Previously unknown Haast tokoeka population discovered using automatic recording devices (ARDs).
| Metric | Total |
|---|---|
| Plots with an acoustic record (i.e. processed ARD recordings) | 1,289 |
| Number of 15-minute recordings processed | 56,256 |
| Incidences - all species of interest | 56,890 |
| Incidences - morepork | 37,853 |
| Incidences - kākā | 5,398 |
| Incidences - long-tailed cuckoo | 5,308 |
| Incidences - kiwi (all species) | 2,622 |
| Incidences - weka | 2,549 |
Data quality
This measure is classified as a partial measure of high accuracy and complies with the data quality guidelines used in New Zealand’s Environmental Reporting framework.
Although thousands of ARD recordings are processed each year, this does not represent all of the recordings collected. Resource constraints mean that only one 15-minute recording from every hour between sunset and sunrise is processed, leaving the other 45 minutes per hour unprocessed. Therefore, the presence of species may be missed at some sites, particularly those species that call infrequently and are rare. Call frequency will vary with species and may also be influenced by the time of year, weather and other factors. Automated identification software (currently under development) may reduce costs and enable a much larger sample of recordings to be processed in the future.
Glossary of terms
Automatic recording device (ARD) is any device that records audio/visual information and does not require the presence of an operator.
Processing is the conversion of recorded information (audio/visual) into data that can be analysed (e.g. a spreadsheet of identified bird species). Processing (species identification) can be automated (performed by a computer algorithm) or manual (performed by a person).
Additional resources
Lee, W.; McGlone, M.; Wright, E. 2005: Biodiversity inventory and monitoring: a review of national and international systems and a proposed framework for future biodiversity monitoring by the Department of Conservation. Landcare Research Contract Report LC0405/122 for the Department of Conservation, Wellington (unpublished). 213 p.
McGlone, M.; Dalley, J. 2015: A framework for Department of Conservation inventory and monitoring: intermediate outcomes 1–5. Landcare Research Contract Report LC2427 for the Department of Conservation, Wellington (unpublished). 75 p.
Mortimer, J.A.J.; Greene, T.C.; van Dam-Bates, P.; Westbrooke, I.M. 2019: Effectiveness and efficiency of avian species detection: a comparison between field observers and automatic recording devices. Notornis 66: 109-128.
Pryde, M.A.; Mortimer, J.A.J.; Greene, T.C.; Thygesen, H.H. 2020: Optimising monitoring times for surveys of ruru (Ninox novaeseelandiae novaeseelandiae). New Zealand Journal of Ecology 44(1): 3401.