Penguin measurements recorded during Robben Island foraging research featured in our recently published paper:
Kate J Campbell, Danielle Farah, Sarah Collins & Nola J Parsons. 2015. Sex determination of African Penguins Spheniscus demersus using bill measurements: method comparisons and implications for use. Ostrich:1-9
Sexing birds in the field can be problematic for those with no sexual distinctive plumage or morphological features, as is the case with the endangered African Penguin. This methods paper clarifies different bill depth measurement techniques currently in use. It also presents a discriminant function that can be used with the traditional bill depth measurement for the species.
One of the findings was that these two bill depth measurements are not interchangeable. When using discriminant functions to sex African Penguins, take care to use the appropriate measurement!
The bill morphology of DNA sexed penguins did not vary geographically, indicating that the discriminant functions described can be used throughout the African Penguins' range in South Africa. Further investigation is needed to see if they can be applied in Namibia.
Reliable sexing methods are pertinent to research into sex ratios, population dynamics and identifying whether there are sex-specific differences in behaviour and survival.