<P> During evolution, hummingbirds have adapted to the navigational needs of visual processing while in rapid flight or hovering by development of an exceptionally dense array of retinal neurons allowing for increased spatial resolution in the lateral and frontal visual fields . Morphological studies showed that neuronal hypertrophy, relatively the largest in any bird, exists in a brain region called the pretectal nucleus lentiformis mesencephali (or nucleus of the optic tract in mammals) responsible for refining dynamic visual processing while hovering and during rapid flight . The enlargement of this brain region responsible for visual processing indicates enhanced ability for perception and processing of fast - moving visual stimuli which hummingbirds encounter during rapid forward flight, insect foraging, competitive interactions, and high - speed courtship . </P> <P> Hummingbirds are highly sensitive to stimuli in their visual fields, responding to even minimal motion in any direction by reorienting themselves in midflight . Hummingbirds' visual sensitivity allows them to precisely hover in place while in complex and dynamic natural environments, functions enabled by the lentiform nucleus which is tuned to fast - pattern velocities, enabling highly tuned control and collision avoidance during forward flight . </P> <P> With the exception of insects, hummingbirds while in flight have the highest metabolism of all animals--a necessity to support the rapid beating of their wings during hovering and fast forward flight . Their heart rate can reach as high as 1,260 beats per minute, a rate once measured in a blue - throated hummingbird, with a breathing rate of 250 breaths per minute, even at rest . During flight, oxygen consumption per gram of muscle tissue in a hummingbird is about 10 times higher than that measured in elite human athletes . </P> <P> Hummingbirds are rare among vertebrates in their ability to rapidly make use of ingested sugars to fuel energetically expensive hovering flight, powering up to 100% of their metabolic needs with the sugars they drink (in comparison, human athletes max out at around 30%). Hummingbirds can use newly ingested sugars to fuel hovering flight within 30--45 minutes of consumption . These data suggest that hummingbirds are able to oxidize sugar in flight muscles at rates high enough to satisfy their extreme metabolic demands . By relying on newly ingested sugars to fuel flight, hummingbirds can reserve their limited fat stores to sustain their overnight fasting or to power migratory flights . </P>

How many times does a hummingbird heartbeat per minute