"Animal substance seems to be the first food of all birds, even the granivorous tribes"

This quote by William Bartram suggests that animals are the main source of food for birds, even those that are mostly seed-eaters. This suggests that birds are omnivorous, which they are not limited to a single type of food. Bartram's observation recommends that birds are opportunistic feeders, and that they will make the most of whatever food sources are readily available to them. This might explain why some birds are able to make it through in a range of environments, as they are able to adjust to various food sources. Bartram's quote likewise suggests that animals are an important part of the food cycle, and that birds rely on them for sustenance. This is an essential suggestion of the importance of protecting animal populations, as they are important to the health of the environment.