Epsilon Archive for Student Projects

Abstract

Great cormorants (Phalacrocorax carbo, hereafter called cormorant) are blamed for depletion of fish populations and have been subject to several control measures, such as culling and oiling of eggs. On the Swedish west coast the European shag (Gulosus aristotelis, hereafter called shag) is present as well. In contrast to the cormorant, the shag is a red listed species.
By examining colonies in the south of Sweden, a study examining egg size variation of cormorant eggs between colonies was conducted, as well as a study comparing shag and cormorant egg sizes to see if that could be a way of separating eggs of the two species from each other.
The study showed that cormorant eggs are larger on the west coast compared to the east coast. It also showed the overlap in size range between shag and cormorant eggs to be too large for it to be a safe method for separating eggs of the species with certainty.
In addition, the study showed that image analysis of photos of eggs could be a possibly effective method for gathering large sets of data in the field in a quick way.
In summary, this study contributed with fundamental knowledge of cormorant biology.
Hopefully the gathering of egg size data can continue beyond this project, building a larger and more established summary of egg size variation.