J Ornithol (2013) 154:19–33 DOI 10.1007/s10336-012-0864-9 ORIGINAL ARTICLE Standardising distance sampling surveys of parrots in New Caledonia Andrew Legault • Jo¨rn Theuerkauf • Emilie Baby • Laetitia Moutin • Sophie Rouys • Maurice Saoumoe´ • Ludovic Verfaille • Nicolas Barre´ • Vivien Chartendrault • Roman Gula Received: 10 September 2010 / Revised: 20 April 2012 / Accepted: 25 May 2012 / Published online: 1 July 2012 Ó The Author(s) 2012. This article is published with open access at Springerlink.com Abstract Standardised surveys are essential for moni- important when estimating parakeet populations. In toring populations and identifying areas that are critical for agreement with existing knowledge on distance sampling, conservation. With the aim of developing a standardised we found line transects to be more efficient than point method of surveying parrots in the rainforests of New transects for estimating the density of parakeets. Our Caledonia, we used distance sampling to estimate densities results indicate that parrots located beyond 50–70 m from of New Caledonian Parakeets (Cyanoramphus saisseti), the transect line have little influence upon density esti- Horned Parakeets (Eunymphicus cornutus), Ouve´a Para- mates. In addition, surveys on roads are likely to under- keets (E. uvaeensis), and New Caledonian Rainbow estimate densities if not corrected for road width. We Lorikeets (Trichoglossus haematodus deplanchii). We generated relatively stable and precise density estimates carried out surveys in the early morning and late after- (CV \ 0.25) with approximately 40–50 detections, yet noon, when parrots were easiest to detect. To minimise additional effort may be warranted under different study errors associated with estimating distances and flock sizes conditions. Although we aimed to improve parrot surveys by ear, we conducted brief searches to locate parrots, in New Caledonia, our suggestions may be useful to other then measured their distance from the transect line. We researchers studying rainforest birds, and can be adapted recorded birds in flight and consider these records to be to suit different species or environments. Communicated by T. Gottschalk. A. Legault Present Address: School of Zoology, University of Tasmania, Private Bag 5, E. Baby Á S. Rouys Hobart, TAS 7001, Australia Socie´te´ Cale´donienne d’Ornithologie, BP 13641, e-mail: [email protected] 98803 Noume´a Cedex, New Caledonia A. Legault Á J. Theuerkauf (&) Á R. Gula M. Saoumoe´ Á L. Verfaille Museum and Institute of Zoology, Polish Academy of Sciences, Province des Iles Loyaute´, Direction du De´veloppement Wilcza 64, 00-679 Warsaw, Poland Economique, BP 50, 98820 We´, Lifou, New Caledonia e-mail: [email protected] e-mail: [email protected] R. Gula L. Verfaille e-mail: [email protected] e-mail: [email protected] E. Baby Á L. Moutin Á S. Rouys N. Barre´ Á V. Chartendrault Conservation Research New Caledonia, BP 2549, Institut Agronomique ne´o-Cale´donien (IAC/CIRAD), 98846 Noume´a Cedex, New Caledonia BP 73, 98890 Paı¨ta, New Caledonia e-mail: [email protected] e-mail: [email protected] L. Moutin V. Chartendrault e-mail: [email protected] e-mail: [email protected] S. Rouys e-mail: [email protected] 123 20 J Ornithol (2013) 154:19–33 Keywords Conservation Á Distance sampling Á conservation (IUCN 2011), yet obtaining reliable estimates New Caledonia Á Parrots Á Survey methods remains an elusive task for certain taxa (Cassey et al. 2007). One of the most commonly used methods to Zusammenfassung approximate animal abundance is index counting, where the observer records the number of individuals detected Standardisierung von ,,Distance Sampling‘‘ zur around a point, or along a transect (Rosenstock et al. 2002), Erfassung von Populationsdichten der Papageien usually over a defined time period. Fauna monitoring Neukaledoniens programs are often dependent upon such indices, as they are useful for comparing temporal and spatial patterns of Standardisierte Erhebungen sind wichtig fu¨r die U¨ berwa- abundance (Karubian et al. 2005), and gauging population chung von Populationsentwicklungen und die Erfassung growth or decline (Amar et al. 2008). In spite of this, von Bereichen, die fu¨r die Arterhaltung von entscheidender indices only provide a relative measure of abundance, and Bedeutung sind. Mit dem Ziel, eine standardisierte Methode do not account for the conspicuousness of the species under zur Erfassung von Papageien der Regenwa¨lder Neukale- study, variations in the surrounding environment, or the doniens zu entwickeln, haben wir mit Hilfe von ,,Distance differing skills of observers (Cassey et al. 2007). Sampling‘‘ Besta¨nde von Neukaledoniensittichen (Cyano- Although indices can play an important role in wildlife ramphus saisseti), Hornsittichen (Eunymphicus cornutus), surveys (Hutto and Young 2003; Johnson 2008), approa- Ouve´a-Sittichen (E. uvaeensis) und Neukaledonien-All- ches that consider the detectability of the species under farbloris (Trichoglossus haematodus deplanchii) gescha¨tzt. study are often considered more appropriate, particularly Wir fu¨hrten die Za¨hlungen am fru¨hen Morgen und spa¨ten when the goal is to estimate absolute numbers (Rosenstock Nachmittag durch, wenn Papageien am leichtesten zu ent- et al. 2002; Thompson 2002; Norvell et al. 2003). Exam- decken sind. Um Fehler bei der Scha¨tzung von Entfernun- ples of these survey techniques include variable strip gen und Gruppengro¨ßen per akustischem Wahrnehmen zu transects (Emlen 1971, 1977), variable circular plots minimieren, haben wir die Papageien schnell gesucht und (Reynolds et al. 1980), double-observer sampling (Nichols dann ihre Entfernung zur Transektlinie gemessen. Wir et al. 2000), independent-observer methods (Alldredge haben fliegende Vo¨gel gleichfalls notiert und denken, dass et al. 2006), and time-of-detection approaches (Farnsworth diese ebenfalls in Scha¨tzungen der Sittich-Popula- et al. 2002; Alldredge et al. 2007a). The method most tionsdichte eingehen sollten. In U¨ bereinstimmung mit commonly used to account for detectability is distance anderen Arbeiten u¨ber ,,Distance Sampling‘‘ fanden wir, sampling, where the observer measures the distance to each dass zur Dichtescha¨tzung der Sittiche Linientransekte animal (or group of animals) detected from a point or effizienter als Punkttransekte sind. Unsere Ergebnisse transect line (Burnham et al. 1980; Buckland et al. 1993, zeigen, dass Beobachtungen von Papageien, die u¨ber 2001). The distances are then used to calculate the proba- 50–70 m von der Transektlinie entfernt waren, wenig bility of encountering an animal as a function of distance Einfluss auf die Dichtescha¨tzungen haben. Daru¨ber hinaus from the transect line. Because the probability of detection unterscha¨tzen Za¨hlungen entlang von Straßen die Popu- declines in a quantifiable and predictable manner, the lationsdichte, wenn die Fahrbahnbreite nicht zur Korrektur detection function can be used to estimate the number of der Entfernungen zur Transektlinie hinzugezogen wird. Wir animals within the area that was effectively surveyed. haben relativ stabile und pra¨zise gescha¨tzte Dichten Distance sampling is advantageous in this regard, as it (CV \ 0,25) mit etwa 40–50 Beobachtungen ermittelt, provides an approximation of animal density, yet it does jedoch ko¨nnten unter abweichenden Studienbedingungen not require the detection of all individuals present, or prior weitere Beobachtungen no¨tig sein. Obwohl es unser Ziel knowledge of the size of the area sampled. The method is war, Populationsdichtescha¨tzungen der Papageien in based on the assumption that individuals on the line or Neukaledonien zu verbessern, ko¨nnen unsere Vorschla¨ge point are detected with certainty, individuals are detected at nu¨tzlich fu¨r Dichtescha¨tzungen anderer Regenwaldvo¨gel their initial location, and distances are measured exactly. sein und entsprechend fu¨r andere Arten oder Lebensra¨ume All of these assumptions may be relaxed under certain angepasst werden. circumstances (Buckland et al. 1993; Thomas et al. 2010), although the reliability of estimates may suffer if they are not met (Ba¨chler and Liechti 2007). Distance sampling has been used to survey a variety of Introduction fauna, and is often employed in bird surveys. It is generally less intrusive than alternative methods such as mist netting Population estimates play a critical role in identifying (e.g. Meyers 1994; Whitman et al. 1997) and mark- species that require protection, and in setting priorities for recapture (e.g. Sandercock and Beissinger 2002), and 123 J Ornithol (2013) 154:19–33 21 provides an efficient means of estimating abundance when effectively. Standardised methods of surveying are essen- it is not feasible to conduct plot searches (e.g. Rodriguez- tial for comparing parrot populations across different time Estrella et al. 1992) or roost counts (e.g. Gnam and Bur- frames or geographical regions as the resulting data can be chsted 1991). In studies of parrots, distance sampling has interpreted with much greater confidence than data col- proven useful for estimating population size (e.g. Walker lected using an assortment of different techniques. Using and Cahill 2000; Rivera-Mila´n et al. 2005), assessing distance sampling, we surveyed New Caledonian Para- abundance in different habitats (e.g. Marsden et al. 2001; keets, Horned Parakeets, and New Caledonian Rainbow Marsden and Symes 2006), and evaluating conservation Lorikeets Trichoglossus haematodus deplanchii (Avibase actions (e.g.