Ornithologist: This bird species is widely thought to subsist primarily on vegetation, but my research shows that this belief is erroneous. While concealed in a well-camouflaged blind, I have observed hundreds of these birds every morning over a period of months, and I estimate that over half of what they ate consisted of insects and other animal food sources. The reasoning in the ornithologist's argument is most vulnerable to criticism on the grounds that the argument ['fails to specify the nature of the animal food sources, other than insects, that were consumed by the birds', 'neglects the possibility that the birds have different patterns of food consumption during different parts of the day and night', "assumes, without providing justification, that the feeding behavior of the birds observed was not affected by the ornithologist's act of observation", "fails to consider the possibility that the birds' diet has changed since the earlier belief about their diet was formed"]