Adaptations change slowly and only over many, many generations. For some native birds, their adaptations actually threaten the birds’ survival. Many New Zealand birds are flightless, and that combined with their slow breeding rates, small clutch sizes and large eggs are some of the factors that affect their survival. These flightless birds and large eggs are easy prey for predators. Many of New Zealand’s nocturnal birds will not thrive in brightly lit urban environments.