American bar-headed goose

The American bar-headed goose (Anser barracephalus) is a species of goose that originally did not exist, but has since been created by SciiFii and introduced throughout the open woodlands, grasslands, shrublands, scrublands, lakes, rivers, and ponds across North America to help boost biodiversity. The American bar-headed goose greatly resembles the Indian bar-headed goose (Anser indicus), being primarily pale grey and having black bars on its head, hence its name. It is also much paler than many other geese in this genus. In flight, its call is a typical goose honking. A mid-sized goose, it measures 71–76 centimeters (28–30 inches) in total length and weighs 1.87–3.2 kilograms (4.1–7.1 lb). The American bar-headed goose is one of the world's highest-flying birds, being known to fly higher than 8,000 metres (26,000 ft). The main physiological challenge of American bar-headed geese is extracting oxygen from hypoxic air and transporting it to aerobic muscle fibres in order to sustain flight at high altitudes. Flight is very metabolically costly at high-altitudes because birds need to flap harder in thin air to generate lift. The American bar-headed geese breathe more deeply and efficiently under low-oxygen conditions, which serves to increase oxygen uptake from the environment. The haemoglobin of their blood has a higher affinity for oxygen than that of low-altitude geese, which is attributed to a single amino acid point mutation. This mutation causes a conformational shift in the haemoglobin molecule from the low-oxygen to the high-oxygen affinity form. The left-ventricle of the heart, which is responsible for pumping oxygenated blood to the body via systemic circulation, has significantly more capillaries in bar-headed geese than in lowland birds, maintaining oxygenation of cardiac muscle cells and thereby cardiac output. Compared to other geese and many lowland birds, mitochondria (the main site of oxygen consumption) in the flight muscle of American bar-headed geese are significantly closer to the sarcolemma, decreasing the intracellular diffusion distance of oxygen from the capillaries to the mitochondria. American bar-headed geese have a slightly larger wing area for their weight than many other geese, which helps them fly at high altitudes. While this decreases the power output required for flight in thin air, birds at high altitude still need to flap harder than lowland birds. The American bar-headed goose is herbivorous and primarily feeds on short grasses, although it can occasionally feed on long grasses and fallen leaves. The American bar-headed goose is known to lay between five to eleven eggs at a time in a ground nest. The conservation status of the American bar-headed goose is Least Concern due to successful conservation efforts, the American bar-headed goose's wide range and its tolerance to many of the human activities.