Calculating census efficiency for river birds: a case study with the White‐throated Dipper Cinclus cinclus in the Pyrénées

Abstract

Using the binomial law we modelled field data to estimate the probability (p̂) of detecting pairs of breeding White‐throated Dippers, and the population size (N̂± confidence limits). The model was divided into two parts according to whether the actual size of the population under study was known or not; in the latter case the truncated binomial model was used. Dipper abundance data were collected from three 4‐km‐long river tracts in the Pyrénées (France) during the breeding seasons of different years. Goodness‐of‐fit tests indicated that the binomial model fitted the data well. For a given visit during the survey, the estimated probability of detecting any pair of Dippers if they were present was always high (0.63–0.94) and constant from year to year but not between sites. Estimations (N̂) of the size of the population provided by the binomial model were very close to that derived from mapping techniques. This study provides the first ever quantification of the number of visits required to detect birds on linear territories: three visits were necessary to detect the whole breeding population.

River birds as potential indicators of local- and catchment-scale influences on Himalayan river ecosystems

“…In each of the two seasons, three visits were made to each river segment (500 m) to increase the detection probability of all species (McCarthy et al 2013). This visit frequency is considered appropriate for species that occupy linear territories along rivers (D'Amico and Hemery 2003). The banks were walked always by the same observer (AS) and surveys were carried out during early morning (06.00 to ± 10.00) and late afternoon (15.00 to ± 18.00) using 8 × 42 binoculars.…”

“…Since their ecology is relatively well known, the effects of environmental change on the distribution, abundance and range of river birds are often readily interpreted Ormerod and Tyler 1993;Colombari and Cordiner 1999;Ormerod et al 2000). Moreover, river birds along montane rivers are easily identified and reliably surveyed by both professionals and citizen scientists creating an opportunity for cost-effective assessment at a range of scales from catchment to regional (D'Amico 2002;D'Amico and Hemery 2003;Vaughan et al 2007). As well as potentially reflecting wider ecosystem integrity and the status of other organisms (Ormerod and Tyler 1993), birds have particular conservation appeal that could help to communicate the importance of river biodiversity more widely (Vaughan et al 2007).…”

Combining surveys of river habitats and river birds to appraise riverine hydromorphology

“…Cramp et al. , 1977–1994); (ii) many species are easily and reliably surveyed without specialist equipment (D'Amico, 2002; D'Amico & Hemery, 2003) and (iii) they are sensitive to pollutants (e.g. Ormerod et al.…”

“…River birds also have pragmatic advantages for routine monitoring, including: (i) their basic ecology is relatively well known (e.g. Cramp et al, 1977Cramp et al, -1994; (ii) many species are easily and reliably surveyed without specialist equipment (D'Amico, 2002;D'Amico & Hemery, 2003) and (iii) they are sensitive to pollutants (e.g. Ormerod et al, 1986;Sorace, Colombari & Cordiner, 1999;Ormerod, Tyler & Jü ttner, 2000).…”

Timing of onset of breeding in three different DipperCinclus cincluspopulations in France

“…In Lorraine, the study sites are on lowland rivers (altitude: 150-300 m asl) while in Auvergne and especially in the Pyrénées, Dippers breed along upland rivers (335-965 and 450-1600 m asl respectively). Study sites are further described in Marzolin (1996), Boitier (1998) andHémery (2003).…”