distance sampling

Use of distance sampling to measure long-term changes in bird densities in a fenced wildlife sanctuary

Long-term data are needed to assess the impact of management initiatives such as mammalian predator-exclusion fences, but long-term monitoring programmes can be difficult to maintain. We used annual line transect distance sampling data collected by undergraduate students to model trends in native bird densities at Bushy Park, New Zealand, from 2002 to 2018, including 14 years of data collection following the installation of a predator-exclusion fence in 2005.

Changes in density of hihi (Notiomystis cincta), tīeke (Philesturnus rufusater) and tūī (Prosthemadera novaeseelandiae) on Little Barrier Island (Te Hauturu-o-Toi), Hauraki Gulf, Auckland, 2005–2013

The hihi/stitchbird (Notiomystis cincta), an endangered New Zealand endemic species, has one self-sustaining population not subject to human intervention, located on Little Barrier Island (Te Hauturu-o-Toi), in the Hauraki Gulf, Auckland. All other hihi populations have been derived from Little Barrier Island and all require active management. Changes in the population of hihi on Little Barrier Island are, therefore, of great conservation interest.

Accounting for detectability when estimating avian abundance in an urban area

Urban areas can support significant bird populations, including species of conservation concern, but urban ecologists have been slow to apply detectability-based counting techniques. We compared abundances and relative abundances of eight urban birds, derived using two commonly applied techniques (fixed-radius point and strip sampling) and distance sampling. We evaluated the influence of habitat and two covariates (observer and whether birds were seen or heard) on detectability. Due to built-up structures in urban areas, point counts are appropriate.

Detection probability for estimating bird density on New Zealand sheep & beef farms

Factors influencing detection probability in line transect distance sampling were investigated to estimate the abundance of four common farmland birds on 12 sheep & beef farms in the South Island of New Zealand. Our primary aim was to evaluate the necessity of employing distance methods to correct for heterogeneity in detection probability.

Designing a bird monitoring scheme for New Zealand’s agricultural sectors

Growing concerns about significant biodiversity decline due to agricultural intensification are increasingly leading consumers to seek agricultural products that are produced sustainably. To raise awareness of sustainable land management and direct policy and research to mitigate adverse impacts, large-scale bird monitoring programmes are being used in Europe. New Zealand’s first farmland bird monitoring scheme was established in 2004 to quantify bird abundance on 98 farms across three sectors (sheep & beef, dairy and kiwifruit).