In 2000 Majerus developed plans for further experiments. In the main experiment in Cambridge from 20012007 Majerus added an experiment to find if bat predation might have skewed the results – this found that bats preyed equally on both forms of the moth. He observed a number bird species preying on the moths. The overall data led him to conclude that differential bird predation was a major factor responsible for the decline in "carbonaria" frequency compared to "typica" in Cambridge during the study period. He described his results as a complete vindication of the peppered moth story, and said "If the rise and fall of the peppered moth is one of the most visually impacting and easily understood examples of Darwinian evolution in action, it should be taught. It provides after all the proof of evolution". 