## 2 Materials and Methods  
### Study Area and Image Data  
In this study, we used a set of cloud-free QuickBird-2 and Worldview-2 images (Figure 1) over sites containing either Adelie or chinstrap penguin colonies (Table 1).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Site** & **Coordinates (Lat, Lon)** & **Species** & **\# of Pairs** & **Source** \\ \hline Barrientos Island in the Aitcho Islands & \(-\)62.381, \(-\)59.776 & Chinstrap & 4047 & [54] \\ \hline Baily Head, Deception Island & \(-\)62.967, \(-\)60.500 & Chinstrap & 50,408 & [55] \\ \hline Spine Island & \(-\)60.594, \(-\)46.020 & Chinstrap & unknown & [56] \\ \hline Hope Bay & \(-\)63.397, \(-\)56.998 & Adélie & \(\sim\)100,000 & [20] \\ \hline Paulet Island & \(-\)63.581, \(-\)55.788 & Adélie & \(\sim\)100,000 & [20] \\ \hline Cape Bird & \(-\)77.229, 166.413 & Adélie & 66,679 & [57] \\ \hline Zavodovski Island & 56.298, \(-\)27.577 &
\begin{tabular}{c} Chinstrap \\ Macaroni \\ \end{tabular} & \(\sim\)600,000 & [58] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Abundance information of candidate sites.  
Figure 1. Geographical setting of study sites and candidates image scenes: (**a**) Aitcho Islands (**b**) Deception Island; (**c**) Cape Bird on Ross Island (**d**) Paulet Island; (**e**) Spine Island; (**f**) Zavodovski Island; and (**g**) Hope Bay. Imagery copyright DigitalGlobe, Inc., Westminster, CO, USA.  
Colonies are generally too large to count all at once, so they are divided up by the surveyor(s) into easily distinguished sub-groups. In each sub-group, the number of nests (or chicks, depending on the time of year) are counted three times using a handheld tally counter. Each count is required to be within 5% of each other and if they are not, the process is repeated. The average of the three counts are used to determine to total number of breeding pairs at a given site. The candidate locations have been previously surveyed on the ground and therefore automated classification could be validated against prior experience, photodocumentation, and existing GPS data on colony locations. Both Adelie and chinstrap penguins form tightly packed breeding colonies, which aids in the interpretation of satellite imagery. Gentoo penguins (_P. papua_) also breed in this area, but their colonies are more difficult to interpret in satellite imagery (even for an experienced interpreter) because they often nest in smaller groupings or at irregular densities that can weaken the guano stain signature. For this reason, while Gentoo penguins breed in the Aitcho Islands, and at other locations that might have been included in our study, we have excluded them from this analysis.  
Candidate scenes that have been radiometrically corrected, orthorectified, and spatially registered to the WGS 84 datum and the Stereographic South Pole projection were provided by the Polar Geospatial Center (University Minnesota). The QuickBird-2 sensor has a ground sampling distance (GSD) of 0.61 cm for the PAN and 2.44 m for MS bands at nadir with 11-bit radiometric resolution. The Worldview-2 hyperspatial sensor records the PAN and the 8 MS bands with a GSD of 0.46 m and 1.84 m at nadir, respectively.