The distribution and abundance of Blue Petrels (<i>Halobaena caerulea</i>) breeding at subantarctic Marion Island

Dilley, Ben J.; Davies, Delia; Schramm, Michael; Connan, Maëlle; Ryan, Peter G.

doi:10.1080/01584197.2017.1298403

Cited by 11 publications

(23 citation statements)

References 34 publications

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“…4.The distribution of blue petrel burrows at Marion Island (adapted from Dilley et al . 2017c) assessed using two sampling techniques: systematic in 2012 (whole-island counts, light shade = low and medium density, dark shade = high and very high density) and random in 2015 (52 strip transects = black lines running inland from the coast; total 144 km). The blue dots indicate the locations of burrows within the 25 m-wide strip transects; those circled in red were not recorded in the systematic survey (numbers indicate burrow counts at these sites).…”

Section: Methodsmentioning

confidence: 99%

“…We did not account for burrow detection probability since the low vegetation allowed observers to easily detect burrows in the 25 m-wide strip transect. For details of systematic surveys for white-chinned and blue petrel burrows, see methods in Ryan et al (2012) and Dilley et al (2017c).…”

Section: Methodsmentioning

confidence: 99%

“…Single burrows often have a few tufts of Poa at the entrance (Smith 1976) that are easily spotted on a Blechnum slope, even at a distance.Burrow entrance characteristics: active burrows showed signs of fresh excavations, feathers, down and droppings; active great-winged petrel burrows have extensive cropping of vegetation adjacent to the burrow entrance in a distinct ‘oblong’ L-shaped strip and typically have a dry tunnel entrance, whereas white-chinned petrels crop vegetation randomly around the burrow entrance and usually have a moat or wet mud in the entrance tunnel (Dilley et al 2017a); blue petrels tend to have very sparse nest lining and consequently very little cropped vegetation around the entrance.Burrow entrance shape and size: great-winged petrel burrow entrances are generally slightly smaller and lower (average 217 ± 50 mm wide by 167 ± 33 mm high) than white-chinned (269 ± 28 mm wide by 207 ± 31 mm high) and grey petrel (238 ± 32 mm wide by 200 ± 29 mm high) burrow entrances (Dilley et al 2017a). Blue petrel entrances are markedly smaller (142 ± 23 mm wide by 110 ± 10 mm high), but are readily distinguished from the even-smaller burrows of Salvin's prions (112 ± 10 mm wide by 96 ± 9 mm high; Dilley et al 2017c). Blue petrels also readily responded to an imitated call-back (also used in the systematic survey; Dilley et al 2017c).…”

Section: Methodsmentioning

confidence: 99%

“…Blue petrel entrances are markedly smaller (142 ± 23 mm wide by 110 ± 10 mm high), but are readily distinguished from the even-smaller burrows of Salvin's prions (112 ± 10 mm wide by 96 ± 9 mm high; Dilley et al 2017c). Blue petrels also readily responded to an imitated call-back (also used in the systematic survey; Dilley et al 2017c). Physical confirmation: this involved observing a bird in the burrow or feeling a response to probing into the nesting chamber of the burrow with a stick (Ryan et al 2012).…”

Section: Methodsmentioning

confidence: 99%

“…In preparation for this, we endeavoured to establish baseline population estimates of three key burrow-nesting petrel species pre-eradication. The distribution and abundance of white-chinned ( Procellaria aequinoctialis L.) and blue ( Halobaena caerulea (Gmelin)) petrels were assessed with independent systematic surveys at Marion Island in 2009 (Ryan et al 2012) and in 2012 (Dilley et al 2017c), respectively. In the present study, we test the effect of sampling strategy (random transect or systematic survey) on population size estimates of burrow-nesting petrels on this large sub-Antarctic island.…”

Section: Introductionmentioning

confidence: 99%

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Clustered or dispersed: testing the effect of sampling strategy to census burrow-nesting petrels with varied distributions at sub-Antarctic Marion Island

et al. 2019

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We compared systematic and random survey techniques to estimate breeding population sizes of burrow-nesting petrel species on Marion Island. White-chinned (Procellaria aequinoctialis) and blue (Halobaena caerulea) petrel population sizes were estimated in systematic surveys (which attempt to count every colony) in 2009 and 2012, respectively. In 2015, we counted burrows of white-chinned, blue and great-winged (Pterodroma macroptera) petrels within 52 randomized strip transects (25 m wide, total 144 km). Burrow densities were extrapolated by Geographic Information System-derived habitat attributes (geology, vegetation, slope, elevation, aspect) to generate island-wide burrow estimates. Great-winged petrel burrows were found singly or in small groups at low densities (2 burrows ha−1); white-chinned petrel burrows were in loose clusters at moderate densities (3 burrows ha−1); and blue petrel burrows were in tight clusters at high densities (13 burrows ha−1). The random survey estimated 58% more white-chinned petrels but 42% fewer blue petrels than the systematic surveys. The results suggest that random transects are best suited for species that are widely distributed at low densities, but become increasingly poor for estimating population sizes of species with clustered distributions. Repeated fixed transects provide a robust way to monitor changes in colony density and area, but might fail to detect the formation/disappearance of new colonies.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Clustered or dispersed: testing the effect of sampling strategy to census burrow-nesting petrels with varied distributions at sub-Antarctic Marion Island

et al. 2019

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Uncertainty in population estimates: A meta‐analysis for petrels

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et al. 2021

Ecol Sol and Evidence

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1. Population estimates are commonly generated and used in conservation science.All estimates carry inherent uncertainty, but little attention has been given to when and how this uncertainty limits their use. This requires an understanding of the specific purposes for which population estimates are intended, an assessment of the level of uncertainty each purpose can tolerate, and information on current uncertainty.2. We conducted a review and meta-analysis for a widespread group of seabirds, the petrels, to better understand how and why population estimates are being used.Globally petrels are highly threatened, and aspects of their ecology make them difficult to survey, introducing high levels of uncertainty into population estimates.3. We found that by far the most common intended use of population estimates was to inform status and trend assessments, while less common uses were trialling methods to improve estimates and assessing threat impacts and conservation outcomes.4. The mean coefficient of variation for published estimates was 0.17 (SD = 0.14), with no evidence that uncertainty has been reduced through time. As a consequence of this high uncertainty, when we simulated declines equivalent to thresholds commonly used to trigger management, only 5% of studies could detect significant differences between population estimates collected 10 years apart for populations declining at a rate of 30% over three generations. Reporting of uncertainty was variable with no dispersion statistics reported with38% of population estimates and most not reporting key underlying parameters: nest numbers/density and nest occupancy. We also found no correlation between uncertainty in petrel population estimates and either island size, body size or species threat status -potential predictors of uncertainty. 6. Key recommendations for managers are to be mindful of uncertainty in past population estimates if aiming to collect contemporary estimates for comparison, to report uncertainty clearly for new estimates, and to give careful consideration to whether a proposed estimate is likely to achieve the requisite level of certainty for the This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Mouse predation affects breeding success of burrow-nesting petrels at sub-Antarctic Marion Island

et al. 2017

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We report the breeding success of four species of burrow-nesting petrels at sub-Antarctic Marion Island where house mice Mus musculus are the sole introduced mammal. Feral cats Felis catus were present on Marion for four decades from 1949, killing millions of seabirds and greatly reducing petrel populations. Cats were eradicated by 1991, but petrel populations have shown only marginal recoveries. We hypothesize that mice are suppressing their recovery through depredation of petrel eggs and chicks. Breeding success for winter breeders (grey petrels Procellaria cinerea (34±21%) and great-winged petrels Pterodroma macroptera (52±7%)) were lower than for summer breeders (blue petrels Halobaena caerulea (61±6%) and white-chinned petrels Procellaria aequinoctialis (59±6%)) and among winter breeders most chick fatalities were of small chicks up to 14 days old. We assessed the extent of mouse predation by monitoring the inside of 55 burrow chambers with video surveillance cameras (4024 film days from 2012–16) and recorded fatal attacks on grey (3/18 nests filmed, 17%) and great-winged petrel chicks (1/19, 5%). Our results show that burrow-nesting petrels are at risk from mouse predation, providing further motivation for the eradication of mice from Marion Island.

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The distribution and abundance of Blue Petrels (Halobaena caerulea) breeding at subantarctic Marion Island

Cited by 11 publications

References 34 publications

Clustered or dispersed: testing the effect of sampling strategy to census burrow-nesting petrels with varied distributions at sub-Antarctic Marion Island

Clustered or dispersed: testing the effect of sampling strategy to census burrow-nesting petrels with varied distributions at sub-Antarctic Marion Island

Uncertainty in population estimates: A meta‐analysis for petrels

Mouse predation affects breeding success of burrow-nesting petrels at sub-Antarctic Marion Island

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