Summary of available data for modelling African penguin Spheniscus demersus populations

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University of Cape Town

This document serves as a compilation of all data currently available as inputs to the African penguin spatial model (Plagányi and Butterworth 2007) being developed. The data are presented here together with some comments as to how they are to be used in the model and notes on their derivation and potential reliability. Note that this is a working group document only and hence should be extended and improved in future, particularly as regards critical evaluation of different data sources. The model presented thus far is spatial in that different populations of penguins are represented, and different levels of movement between these populations are modelled. The main focus of the model is on Dassen and Robben Islands, which were originally combined for reasons of simplicity and because of their close proximity to each other, suggesting that the effects of external factors such as food availability would be highly correlated between the two. However, data that have recently become available indicate differences between these two colonies which suggest that it may no longer be appropriate to pool the two; hence they are being split in an updated model. The third population is Dyer Island because it has the next largest numbers of penguins, recent declines in the population there are of concern and it is considered an important breeding site for penguins given the eastward shift of sardines. The fourth population is Boulders. Although relatively small, this colony was considered important to include because of its position, its role as the focus of several other studies and because penguins are known to have moved from Dyer Island to Boulders, Robben and Dassen, and hence it is useful to quantify to what extent movement of birds away from Dyer Island could account for observed declines at Dyer and increases at these other colonies. An Algoa Bay component can also be linked to the model if required.