Marine animals are “bio-indicators” of climate change in the Antarctic. The abundance of nutrients in their excreta, such as carbon (C) and nitrogen (N), promotes the emission of greenhouse gases (GHGs), including methane (CH4) and nitrous oxide (N2O). Adelie penguins are important marine animals, and their colonies have therefore become potential “hotspots” of GHG emissions. Field observations have been conducted to study penguin excreta as a source of CH4 and N2O emissions in the Antarctic Peninsula. However, due to the lack of penguin population data, the total GHG emissions have not been estimated at the regional scale. With the development of remote sensing monitoring techniques in recent years, high-resolution satellite imagery and aerial photographs have made it possible to monitor penguin populations in the Antarctic, with the results used as a foundation to estimate GHG emissions. Inexpressible Island, a small, rocky island on the shore of the Ross Ice Shelf in Terra Nova Bay, Victoria Land, Antarctica, houses an important colony of Adelie penguins. This study extracted information about the penguins from aerial photographs using a pixel-oriented RGB (red, green, and blue) color space model of Victoria Land. Adelie penguin populations on Inexpressible Island could be estimated via a penguin shadow analysis in the RGB model. To validate the accuracy of the RGB model, we randomly selected several images and used the RGB method alongside an artificial visual interpretation method, with the results from both methods compared using the relative deviation index. In addition, a GHG model was developed to estimate CH4 and N2O emissions from Adelie penguins. The model included a variety of parameters, such as the CH4 and N2O fluxes from penguin excreta, the population number, the fresh weight of excreta produced by a penguin each day, and the duration of CH4 and N2O emissions from the excreta.