http://www.gardening-for-wildlife.com/hummingbird-brain.html wrote:
They're Not Albert Einstein,
but the Hummingbird Brain is Unique.
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A hummingbird's brain is smaller than a pea, what kind of a brain could this diminutive bird possibly have? This bird's brain is studied for episodic memory—memory that encodes particulars of what, where, and when—used to be considered exclusively human.
Biologists working with corvids—birds in the family that includes jays, crows, nutcrackers, and magpies—began to wonder about that. Some corvid species are food-cachers: they hide stashes of acorns or pine nuts in summer or fall to sustain themselves during winter and early spring, when other food is scarce. When they returned to their cache, had they made a random search or had they remembered where the items had been hidden?
Better-than-chance retrieval performance suggested that birds like western scrub-jays, pinyon jays, and Clark’s nutcrackers had a well-developed spatial memory.
The brains of these species have a larger-than-average hippocampus, an area thought to be responsible for processing memory. Corvids have relatively big brains for birds (and scrub-jays have large hippocampi even for corvids). If you’d expect any kind of bird to be capable of memnonic prodigies, it would probably be a scrub-jay.
However, episodic-like memory may not be unique to jays.
Very similar processes have now been documented in, of all things, hummingbirds.
The hummingbird's brain?
In a study that appeared in Current Biology, Susan Healy and Jonathan Henderson of the University of Edinburgh describe their fieldwork with rufous hummingbirds in the Canadian Rockies. (The rufous hummer is an early spring migrant through the Bay Area; its close relative, the Allen’s hummer, stays to nest). Healy and Henderson placed eight artificial flowers in an alpine meadow patronized by hummingbirds. Some of the “flowers” were refilled with hummer food at 10-minute intervals, others at 20-minute intervals.
Can a hummingbird's brain actually think?
Tallying visits by three male rufous hummers, the researchers found the birds could distinguish between the 10-minute and 20-minute “flowers” and remember their locations and when they had last drained them. Over several days, they reliably returned to the “flowers” just after they had been refilled; once again, a matter of what, when, and where.
It makes sense for hyperactive birds like hummers to maximize their foraging efficiency. Return to a flower too soon, and the nectar won’t have been replenished; too late, and a rival may have beaten you there. With a long migration route and a short breeding season, rufous hummers can’t afford to waste time and energy in the search for food.
Healy and Henderson point out that their male hummers were able to track the timing of nectar supplies while defending their territories and courting females. So you have not only episodic memory but serious multitasking.
Several studies show hummers know when a flower is ready.
All this when a hummingbird's brain is smaller than a pea.
No one knows how large a hummer's hippocampus is, absolutely or relatively. But the bird doesn’t have a whole lot of neurons to work with. It may not the size of the hummingbird brains that enables these kinds of mental processes, but the complexity of the wiring.
Smaller does not necessarily equate to dumber: the minuscule brain of the hummer appears to have the bandwidth to do what it needs to do.
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Hummers have song?
Back to the brain we go.
Vocal learning has been repeatedly demonstrated in two bird orders, Passeriformes (specifically the oscine songbirds) and Psittaciformes (parrots), and is believed to occur in a third, the Trochiliformes (hummingbirds). By comparing brain structures in these three bird orders, which are widely separated from one another on the avian family tree. Rockefeller University biologist Claudio Mello and his colleague Erich Jarvis, of Duke University, have shown that the same areas that control song learning and production in songbirds and parrots are also present in hummers. A finding that strengthens the case for vocal learning in our hummers.
Most people are surprised to learn that these tiny birds have songs. The songs aren't particularly loud and you sort of have to know what to listen for. They are higher pitched than those of songbirds, but the songs are amazingly rich, and in some species they can be quite complex.
In the 1950s biologists began to investigate the processes by which birds imitate the sounds they hear and incorporate them into songs. Appropriately enough, that work began with songbirds, a suborder that includes almost half the nearly 8,500 living species of birds.
W. H. Thorpe, of the University of Cambridge, was the first to demonstrate learning in birds by performing what is now considered to be a classic experiment, involving the isolation of male chaffinches (European songbirds) in soundproof chambers equipped with speakers. Young chaffinches that heard recorded chaffinch songs were able to imitate these songs. Birds deprived of the recordings developed abnormally simple songs.
Next was the hummer's brain.
Isolation experiments are exceedingly difficult to do with hummingbirds, however. Because of their extraordinarily fast metabolism. Baby hummers must be fed every ten minutes around the clock. In 1990, this type of experiment was conducted on one species of trochilid, the Anna's hummingbird (Calypte anna).
The late Luis Felipe Baptista, of the California Academy of Sciences, and Karl Schumann, at the Zoologisches Forschungs-institut in Bonn, Germany, found that a male Anna's raised in isolation produced a much simpler song than did wild males.
The song was also very different from that of three males hand-raised together. The outcomes suggested that the males were imitating each other's vocalizations--evidence that the brain can learn songs. In the 1970's and 1980's, Fernando Nottebohm, of Rockefeller University, and several colleagues set about mapping the parts of the hummingbird's brain involved in the singing process.
The researchers identified six anatomically distinct areas--clusters of cells called nuclei--in the forebrain of songbirds.
The hummer's brain nuclei are organized into two distinct paths: The posterior pathway, which controls song production, and the anterior pathway, which controls song learning. Together these pathways form a song control system that must be intact if birds are to sing the songs they've learned.
Forebrain nuclei similar in structure and location have also been found in the budgerigar (an Australian parakeet). No such nuclei have been found in the birds most closely related to songbirds, the suboscines (woodcreepers, ovenbirds, antbirds), or in other nonlearners of songs such as pigeons and doves (order Columbiformes) and chickens, turkeys, and quails (order Galliformes).
Before Mello and Jarvis, no one had bothered to look for these nuclei in a brain.
Working with songbirds in the 1990s, bird researchers added a novel tool to their toolbox. A gene called ZENK, that would make the search for nuclei in a hummingbird's brain much easier. Nottebohm, Mello, and Jarvis noticed that the number of activated ZENK genes in certain areas of the brain was very low when the songbirds were quiet.
When the birds sang or heard songs, however, ZENK activity increased. By measuring the levels of activated ZENK in specific locations.
The researchers were able to see the previously identified nuclei "in action." ZENK gave the researchers a window into the brain, enabling them to see how certain behaviors set into motion the molecular activity of cells in specific brain areas.
Hovering
In 2006, a couple of Canadian scientists dug into some hummingbird brains this is what they found.
"This was a very exciting moment for us," said Dr. Doug Wong-Wylie, Canada Research Chair in Behavioural and Systems Neuroscience and psychology professor at the University of Alberta. "As soon as we looked at these specimens it was obvious that something was different in this bird's brain than other species."
Wong-Wylie and Dr. Andrew Iwaniuk, also from the Department of Psychology in the Faculty of Science, compared the hummer brain to 28 other bird species.
Hummers are well known for their wing speed and ability to hover and fly forward and backward with more precision than a helicopter. It is critical that the hummer remain perfectly still as it feeds itself while darting in and out of flower blossoms with pinpoint accuracy. The bird must be able to maintain a stable position space, despite the fact that their wings are beating 75 times per second and that disruptive effects such as wind gusts could throw them off.
Much work has been done on the its physiological make up--such as its enlarged heart, high metabolic rate and specialized wing kinematics--but nothing has been done on the neural specializations of the bird.
"Part of the reason this type of work hasn't been done before is because of access to the birds," said Iwaniuk. "In Canada especially they tend to be uncommon, they come from exotic locales and they are not easy to catch, so we were very fortunate to be able to study the specimens we did."
The scientists found that a specific nuclei--one that detects any movement of the entire visual world--was two to five times bigger in the hummingbird than in any other species, relative to brain size.
The brain is smaller than a fingertip. The doctors reasoned that it is this nucleus helps the hummingbird stay stationary in space, even while they're flying. These birds must have a good optomotor response considering they are stationary 90 per cent of the time. This specific nuclei is likely responsible for that.>>