Standardising distance sampling surveys of parrots in New Caledonia

Abstract

Standardised surveys are essential for monitoring populations and identifying areas that are critical for conservation. With the aim of developing a standardised method of surveying parrots in the rainforests of New Caledonia, we used distance sampling to estimate densities of New Caledonian Parakeets (Cyanoramphus saisseti), Horned Parakeets (Eunymphicus cornutus), Ouvéa Parakeets (E. uvaeensis), and New Caledonian Rainbow Lorikeets (Trichoglossus haematodus deplanchii). We carried out surveys in the early morning and late afternoon, when parrots were easiest to detect. To minimise errors associated with estimating distances and flock sizes by ear, we conducted brief searches to locate parrots, then measured their distance from the transect line. We recorded birds in flight and consider these records to be important when estimating parakeet populations. In agreement with existing knowledge on distance sampling, we found line transects to be more efficient than point transects for estimating the density of parakeets. Our results indicate that parrots located beyond 50-70 m from the transect line have little influence upon density estimates. In addition, surveys on roads are likely to underestimate densities if not corrected for road width. We generated relatively stable and precise density estimates (CV \ 0.25) with approximately 40-50 detections, yet additional effort may be warranted under different study conditions. Although we aimed to improve parrot surveys in New Caledonia, our suggestions may be useful to other researchers studying rainforest birds, and can be adapted to suit different species or environments. Communicated by T. Zusammenfassung Standardisierung von ,,Distance Sampling'' zur Erfassung von Populationsdichten der Papageien Neukaledoniens Standardisierte Erhebungen sind wichtig für die Ü berwachung von Populationsentwicklungen und die Erfassung von Bereichen, die für die Arterhaltung von entscheidender Bedeutung sind. Mit dem Ziel, eine standardisierte Methode zur Erfassung von Papageien der Regenwälder Neukaledoniens zu entwickeln, haben wir mit Hilfe von ,,Distance Sampling'' Bestände von Neukaledoniensittichen (Cyanoramphus saisseti), Hornsittichen (Eunymphicus cornutus), Ouvéa-Sittichen (E. uvaeensis) und Neukaledonien-Allfarbloris (Trichoglossus haematodus deplanchii) geschätzt. Wir führten die Zählungen am frühen Morgen und späten Nachmittag durch, wenn Papageien am leichtesten zu entdecken sind. Um Fehler bei der Schätzung von Entfernungen und Gruppengrößen per akustischem Wahrnehmen zu minimieren, haben wir die Papageien schnell gesucht und dann ihre Entfernung zur Transektlinie gemessen. Wir haben fliegende Vögel gleichfalls notiert und denken, dass diese ebenfalls in Schätzungen der Sittich-Populationsdichte eingehen sollten. In Ü bereinstimmung mit anderen Arbeiten über ,,Distance Sampling'' fanden wir, dass zur Dichteschätzung der Sittiche Linientransekte effizienter als Punkttransekte sind. Unsere Ergebnisse zeigen, dass Beobachtungen von Papageien, die über 50-70 m von der Transe...

Congo Grey ParrotPsittacus erithacusdensities in oil palm plantation, agroforestry mosaic and protected forest in Southwest Cameroon*

“…for the Congo Grey Parrot Psittacus erithacus in three different landscape types (KNP – Korup National park, AFM – agroforestry matrix, OPP – oil palm plantation) in SW Cameroon. Numbers result from using data from stationary flocks (only perched flocks included, see Legault et al (2013) and Marsden et al (2015)). D and N estimated using the model half-normal (cosine) from a distance data subset truncated to w = 127 m and estimated detection probability of P = 0.55.…”

“…Following the procedures employed by Legault et al (2013) and Marsden et al (2015), we collected data from transects, and report both encounter rates and densities for stationary parrot flocks. These walks follow paths of least resistance through dense habitat (Walsh and White 1999).…”

“…We used a GPS device to record the paths walked and measured perpendicular distances from the transect line to Grey Parrot flocks with a rangefinder. To increase accuracy and discernment, all transects were walked at least once by two observers (Legault et al 2013). Transects were walked directly after dawn between 06h00 and 10h00, and before dusk between 16h00 and 19h00, when parrot activity was highest.…”

Revisiting methods for estimating parrot abundance and population size

“…Rivera-Milán et al 2005;Berg and Angel 2006;Matuzak and Brightsmith 2007), and instigated further investigations (e.g. Marsden 1999;Cougill and Marsden 2004;Legault et al 2013). Since 1997, technological advances have allowed researchers to carry out new types of surveys (e.g.…”

Population monitoring and modelling of yellow‐shouldered parrot on Bonaire, Caribbean Netherlands

“…all parrots and all roosts on Bonaire). Secondly, many parrots do not display typical roosting behaviour and remain scattered in clusters of variable sizes during the counts; and even in accessible roosting sites with open vegetation, parrot counts are likely incomplete (Casagrande and Beissinger 1997, Marsden 1999, Rivera-Milán et al 2005, Legault et al 2013. Lastly, the parrot roost counts have been used to assert that the population has been "increasing steadily over the past 15 years" (Roberts et al 2014: 39), while not accounting for observation and process error variances in trend modelling and estimation (Kéry et al 2009, Kéry and Schaub 2012, Hostetler and Chandler 2015, Rivera-Milán et al 2016.…”