Flightless bird that require a significant amount of overall metabolic energy, ratites decrease their basal metabolic rate and conserve energy. A study looking at the basal rates of birds found a significant correlation between low basal rate and pectoral muscle mass in kiwis. On the contrary, flightless penguins exude an intermediate basal rate. This is likely because penguins have well-developed pectoral muscles for hunting and diving in the water. For ground feeding birds, a cursorial lifestyle is more economical and allows for easier access to dietary requirements. Flying birds have different wing and feather structures that make flying easier, while flightless birds'
Birds of the Amazon birds that breed in the northern and southern hemisphere but migrate to the Amazon rainforest for food and shelter that are not available at their breeding places during cold months. Migrating birds greatly rely on rainforests for food, rest and recovery after their dangerous migration during which they can lose 30% of their body weight. Since the 1970s, cattle pasture has been the leading cause of deforestation in the Brazilian Amazon. Land is often cleared for investment purposes due to pastureland prices exceeding forest land prices. In this case, large amounts of forest are torn down and replaced with savanna