Sex determination of African Penguins<i>Spheniscus demersus</i>using bill measurements: method comparisons and implications for use

Campbell, Kate J.; Farah, Danielle; Collins, Sarah A.; Parsons, Nola J.

doi:10.2989/00306525.2015.1108371

Cited by 9 publications

(9 citation statements)

References 26 publications

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“…Birds were captured prior to a departure, weighed and equipped with a logger taped to their lower back feathers (Tesa ® tape, 4651). Devices were removed after several days (mean ± SD: 4.38 ± 1.21 d), and additional morphometric measurements (bill depth and length, flipper, weight) were taken to assess gender (see Pichegru et al 2013, Campbell et al 2016, and details of protocol in Traisnel & Pichegru 2018). Overall, we tracked 59 breeding adults for a total of 168 tracks (2−6 trips ind.…”

Section: Data Collectionmentioning

confidence: 99%

Success comes with consistency in hard times: foraging repeatability relates to sex and breeding output in African penguins

Traisnel¹,

Pichegru²

2019

Mar. Ecol. Prog. Ser.

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The concept of individual behavioural consistency has received a great deal of attention in the past 2 decades. However, the fitness benefits of being consistent in varying environmental conditions remain poorly explored. Such information is strongly relevant to our understanding of ecological processes, but also for predicting how some individuals and populations cope with environmental changes. We investigated short-term consistency in foraging behaviours of African penguins Spheniscus demersus at population and individual levels on Bird Island (Algoa Bay, South Africa) between 2015 and 2017, and related individual levels of consistency to reproductive outputs. Short-term overall consistency in foraging behaviour across individuals of the same population (population level) was generally moderate, although it was high for bearing (i.e. direction) towards the furthest point of the foraging trip. At the individual level, foraging consistency differed between years and was higher when environmental conditions were less profitable. Females were more flexible in their foraging behaviours than males. Overall, these results suggest that both intrinsic and extrinsic factors are responsible for inter-individual differences in foraging consistency in African penguins. Chicks of parents that were consistent in their foraging trip duration had higher growth rates than those of more flexible individuals when conditions were poor. It is not clear whether penguins adapt their level of short-term consistency at sea to the changing conditions or maintain their strategy across years. However, our results have revealed a reproductive advantage of individual foraging consistency during a year when resources were poor. For the first time, we have identified a potential mechanism to explain why some African penguins may cope better than others during poor environmental conditions.

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Section: Data Collectionmentioning

confidence: 99%

Success comes with consistency in hard times: foraging repeatability relates to sex and breeding output in African penguins

Traisnel¹,

Pichegru²

2019

Mar. Ecol. Prog. Ser.

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“…Given the close proximity of northern rockhopper penguins' breeding sites in the South Atlantic Ocean, the geographic variation in sexual size differences we found in penguins breeding in the islands was unexpected. A recent study on African penguins showed no geographic morphological variation across their breeding range (Campbell et al 2016).…”

Section: Discussionmentioning

confidence: 96%

“…the tail length, or parameters that might fluctuate seasonally such as body mass (e.g. Poisbleau et al 2010, Pichegru et al 2013, Campbell et al 2016. BL was the parameter that contributed most to the dissimilarity between the sexes and has more confined landmark locations than BD; hence, measurements of this parameter would be expected to vary less be tween observers (Arnqvist & Mårtensson 1998).…”

Section: Discussionmentioning

confidence: 99%

“…Given that previous studies predominantly found measurements of bill length (BL) and bill depth (BD) to have the great-est sexual size differences (e.g. Poisbleau et al 2010, Campbell et al 2016, Cappello & Boersma 2018 , Table 1), we focused on these 2 morphometrics while simultaneously using genetic analysis to confirm the sex of study individuals in order to test the reliability of the obtained discriminant functions and examine differences in measurements among islands.…”

Section: Introductionmentioning

confidence: 99%

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Sexual and geographic dimorphism in northern rockhopper penguins breeding in the South Atlantic Ocean

Steinfurth

Booth

White

et al. 2019

Endang. Species. Res.

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The Endangered northern rockhopper penguin Eudyptes moseleyi, like all penguins, is monomorphic, making sex determination of individuals in the field challenging. We examined the degree of sexual size dimorphism of adult birds across the species' breeding range in the Atlantic Ocean and developed discriminant functions (DF) to predict individuals' sex using morphometric measurements. We found significant site-specific differences in both bill length and bill depth, with males being the larger sex on each island. Across all islands, bill length contributed 78% to dissimilarity between sexes. Penguins on Gough Island had significantly longer bills, whilst those from Tristan da Cunha had the deepest. Island-specific DFs correctly classified 82−94% of individuals, and all functions performed significantly better than chance. The model for Nightingale Island correctly classified the greatest proportion of individuals (94−95%), while that for Tristan da Cunha performed the poorest (80−82%). A discriminant function derived from all sites accurately sexed 86−88% of northern rockhopper penguins achieving similar accuracy to island-specific functions. While molecular techniques conclusively determine an individual's sex, morphometric measurements can provide a reliable estimate with close to 90% accuracy using a method that is less invasive and requires little technical expertise. Sexing is an important tool for meaningful interpretation of ecological data. Consideration of sex-specific differences in future studies will aid investigation of a potential sex-dependent vulnerability in this Endangered species.

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“…counted penguins twice daily, at sunrise and sunset, noting all visible penguins every five minutes and all heard EDS vocalisations and identifying all callers within the radius around the AM device for half an hour per site, resulting in a total of n = 48 observation periods. Since visual sexing of African penguins is unreliable [ 44 ], both males and females were counted. Observation times were shifted with sunrise and sunset in a way that the first two sites were surveyed in the half hour before and after sunrise, while the third site was surveyed either in the half hour before or after sunset.…”

Section: Methodsmentioning

confidence: 99%

Effect of Environmental Variables on African Penguin Vocal Activity: Implications for Acoustic Censusing

Hacker,

Terranova,

Petersen

et al. 2023

Biology

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Global biodiversity is in rapid decline, and many seabird species have disproportionally poorer conservation statuses than terrestrial birds. A good understanding of population dynamics is necessary for successful conservation efforts, making noninvasive, cost-effective monitoring tools essential. Here, we set out to investigate whether passive acoustic monitoring (PAM) could be used to estimate the number of animals within a set area of an African penguin (Spheniscus demersus) colony in South Africa. We were able to automate the detection of ecstatic display songs (EDSs) in our recordings, thus facilitating the handling of large datasets. This allowed us to show that calling rate increased with wind speed and humidity but decreased with temperature, and to highlight apparent abundance variations between nesting habitat types. We then showed that the number of EDSs in our recordings positively correlated with the number of callers counted during visual observations, indicating that the density could be estimated based on calling rate. Our observations suggest that increasing temperatures may adversely impact penguin calling behaviour, with potential negative consequences for population dynamics, suggesting the importance of effective conservation measures. Crucially, this study shows that PAM could be successfully used to monitor this endangered species’ populations with minimal disturbance.

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Sex determination of African PenguinsSpheniscus demersususing bill measurements: method comparisons and implications for use

Cited by 9 publications

References 26 publications

Success comes with consistency in hard times: foraging repeatability relates to sex and breeding output in African penguins

Success comes with consistency in hard times: foraging repeatability relates to sex and breeding output in African penguins

Sexual and geographic dimorphism in northern rockhopper penguins breeding in the South Atlantic Ocean

Effect of Environmental Variables on African Penguin Vocal Activity: Implications for Acoustic Censusing

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