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Empire, United States

Calls and playback-response behaviour of breeding wedge-tailed shearwaters (Puffinus pacificus) were studied at Muttonbird Island, Coffs Harbour, New South Wales, Australia. Burrow calls were recorded from 45 females and 60 males. Male calls averaged higher in fundamental frequency and longer in note lengths than female calls, although ranges overlapped. Playback experiments demonstrated sexual recognition, with incubating females mostly responding to female playbacks. Males responded to both female and male calls. Ratios of between- to within-subject variation suggested that individual vocal signatures could be encoded in timing and some frequency parameters. Playback experiments demonstrated a "dear enemy" effect, where shearwaters in burrows were more responsive to stranger rather than neighbour calls. Wedge-tailed shearwater calls are informative and further studies are encouraged for other southern hemisphere breeding shearwaters. © The Ornithological Society of New Zealand Inc.

Birds were counted with transect, point count and two-hectare search methods at one dry sclerophyll forest site and one subtropical rainforest site in northern New South Wales. Five population density estimators and one reporting rate index were evaluated. True densities were unknown and comparisons focused on variation between methods. Distance sampling line transect and point transect estimates averaged 2.24 and 5.12 times greater than unadjusted strip transect and circular plot densities respectively. Point transects were likely affected by bird movements and densities averaged 2.62 times greater than line transects. Two-hectare search densities were comparable to line transects in dry sclerophyll forest and to strip transects in rainforest. Relative density estimates were more consistent, with strong correlations (r = 0.71-0.95) between all five estimators. Two-hectare search reporting rates correlated strongly with density, although the relationship was curvilinear. Reporting rates confound abundance and occupancy and should be interpreted cautiously. Pilot studies are recommended to test assumptions and expose the strengths and weaknesses of different bird survey methods. Transects were more efficient than point counts and two-hectare searches for estimating relative densities in this study.

Totterman S.L.,179 Reedy Creek Road
Marine Ornithology | Year: 2015

Identifying female and male birds can be very helpful in field studies. However, sexual differences in size and plumage are subtle in most petrels. Four field methods were compared for sexing breeding Wedge-tailed Shearwaters Puffinus pacificus on Muttonbird Island, New South Wales, Australia: cloaca inspection, biometrics, acoustics and playback-response. Accuracy was evaluated against molecular tests. A biometric discriminant function combining bill depth and total head length sexed 81% of birds (79 of 98) correctly. Males averaged 3% larger than females, with overlapping size ranges. Sexual differences in cloacal size were not always obvious because female cloacae gradually relapse after laying and males struggling in the hand can present extruded cloacae. Cloacal sexing was 86% correct (93 of 108 birds). Withinpair comparisons of biometrics and cloacal size increased sex classification accuracy for twice the effort (two birds evaluated rather than one). An acoustic discriminant function combining fundamental frequency and note length from burrow call recordings sexed 97% of birds (102 of 105) correctly. A novel playback-response test was efficient and sexed 94% of birds (47 of 50) correctly. © 2015, Marine Ornithology. All rights reserved.

A species inventory aims to list all of the species present in an area over some period of time. Complete results are rarely practical and estimators can be applied to predict total species richness. In this study four survey methods were compared in a northern New South Wales dry sclerophyll forest: standardised search, two-hectare search, transects and point counts. Total sampling time was equal (560 minutes) for all methods. Three non-parametric estimators were evaluated: Chao2, first-order jacknife and second-order jackknife. The quality of inventories and estimates was strongly affected by search method and sampling effort. True species richness was approximately 42 species. The standardised search recorded 35 species, transects 34, point counts 32 and the two-hectare search 27 species. Estimates of total species richness were more accurate at high completeness (when more than 75 per cent of species present were recorded) and when there were few unique records. The firstorder jackknife was most accurate at high completeness and the second-order jackknife at low completeness. Large area, active search methods, patch-scale sampling, results-based stopping rules and species richness estimation are recommended to improve bird species inventories.

Totterman S.L.,179 Reedy Creek Road
Marine Ornithology | Year: 2016

External biometrics have many applications in ornithology, and study skins are a major source of these measurements. However, measurements can be imprecise, and skins tend to shrink when they dry — two problems rarely investigated for petrels (family: Procellariidae). This study examined measurement error and shrinkage for 15 biometrics, using Short-tailed Shearwater Puffinus tenuirostris as the subject species. Random measurement error, defined as the variability of repeated measurements of a particular character taken on the same individual relative to its variability among individuals in a particular group, ranged from 0.3% for head plus bill length in dry specimens to 36% for tarsus width in freshly dead birds. Shrinkage of skin specimens stabilised within 2-5 months after preparation. Average fresh-dry shrinkage ranged from 0.2% for head plus bill to 12% for tarsus height. A new method was used to estimate shrinkage variability among individuals. “Shrinkage variation,” defined as the proportion of unexplained variance (1 - r2) in the correlation between paired fresh and dry measurements of a particular character after correcting for measurement error, ranged from 0% for wing chord to 33% for bill base width. More robust biometrics from this study were measurements of large, inflexible characters with well-defined measurement “landmarks.”. © 2016, Marine Ornithology. All rights reserved.

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