The passage suggests which of the following about "canopy complexity"? A. Decreased canopy complexity can lead to a greater abundance of ground foragers. B. Increased canopy complexity usually helps in retaining a more natural bird diversity. C. Increased canopy complexity is usually detrimental to ground-nesting species. D. Differences in canopy complexity between two regions are not always obvious. E. Differences in foraging behavior among foliage-foraging birds can lead to differences in canopy complexity.