The top 50 centimeters of soil on Tiliga Island contain bones from the native birds eaten by the islanders since the first human immigration to the island 3, 000 years ago. A comparison of this top layer with the underlying 150 centimeters of soil -- accumulated over 80, 000 years -- reveals that before humans arrived on Tiliga, a much larger and more diverse population of birds lived there. Thus, the arrival of humans dramatically decreased the population and diversity of birds on Tiliga.
Many of the bird species that disappeared from Tiliga did not disappear from other, similar, uninhabited islands until much later most seriously weakens the argument.