TeamC, your students are really digging in to the meat of the matter!
In addition to the taste buds info from
Tulsaducati and
JFrancl, I found this info posted by
FinnBMD in the "
Bald Eagle Anatomy & Physiology" thread on the Mods Education board in Forum. It has some related info about raptors and the possible relationships between their senses of smell and taste. I quoted
Finn's post from that thread below, as well as the link directly to it.
See the bottom section of that post for "Smell and Taste" - I enlarged that text. I thought it was really fascinating. Food for thought. Hmmm.
http://www.raptorresource.org/forum/index.php/topic,1808.msg287593/topicseen.html#msg287593Hearing: a Bald Eagle's hearing is not quite as highly developed as its vision (more about this later from jf), but is still acutely sensitive. Ears are openings in the skull below and behind the eye, near the jaw hinge; they are covered by sparse feathers called ear coverts or auriculars. The muscles that anchor these feathers form a shallow funnel which directs sounds into the ear and protect the ear from air turbulence during flight.
There are 3 parts to the avian ear: the external ear (which is hidden by the auriculars) and carries sound toward the tympanic membrane or eardrum which covers the middle ear. Sound waves are transmitted by the eardrum into the inner ear where they are transformed into nerve impulses that are transmitted to the brain. The inner ear is that part of the avian ear which is the sensory receptor for both balance/orientation and sound.
Many studies have been done to determine just how well birds can hear. To keep it simple, diurnal birds (those mainly active during the day like Bald Eagles) have hearing about equal to humans; nocturnal birds (like owls) have much more sensitive hearing. According to avian vet Scott Ford, birds are less sensitive in general to the wide range of sound frequencies that humans and other mammals can hear. But they are more sensitive to differences of intensities within the narrower range that they can hear. Hearing ranges differ depending on the source consulted, but there seems some consensus that birds' hearing is limited to about 12,000 Hz versus human hearing which ranges up to about 18,000 Hz. In general, according to Cornell University, most birds have the greatest sensitivity to sounds ranging between 1,000 and 5,000 Hertz--which is close to the top 2 octaves of a piano.
I've always thought Scott Nielsen's observation in A Season with Eagles was interesting about Bald Eagles' hearing: Nielsen writes that they never just react to sound itself but always follow any sound they hear with a close visual examination of where the sound came from--if their visual observation confirms a threat, they will react and leave the area.
Smell and Taste: the part of the avian brain that is related to birds' ability to smell is quite small. According to Cornell, lab tests have shown that in general birds may only be one-third to two-thirds as sensitive to odors as some fish and mammals, including humans. Raptors may have cells in a nostril cavity that detect scents so that they can smell the prey that they hold in their beak. Nick Fox, who is a falconer, breeder, raptor biologist and author of Understanding the Bird of Prey, reports seeing various hawks he has trained pick up and reject meat that they have held in the horny tip of their beak in such a way that they couldn't have possibly tasted it. For Fox, this means that they must have some sense of smell in their mouth or nares (nostrils). Fox writes that there are scent-detecting cells in one of the cavities of their nares. This cavity "opens directly into the roof of the mouth and it is thus possible that the bird is able to smell, as well as taste the food actually in its mouth" (p. 23). Avian vet Scott Ford says that raptors' beaks and mouths are lined with touch sensors and that they may rely more on the texture and appearance of their food than on its taste and smell. Like Fox, Ford claims that the olfactory sensors in their nasal passages mean that birds may be able to smell food while it is held in their beak and this allows them to reject spoiled meat without actually tasting it. If you think about the way a raptor eats its prey, they don't 'chew' their food but actually manipulate it in their beak and tear off large chunks or pieces and then swallow it quickly without processing it or taking much time to taste.
What a Bald Eagle may be 'lacking' in these 2 primary senses, it more than makes up for with its extraordinary vision--and I know jf has some interesting information to share with you about that!
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Topic: Education In Action (Read 38995 times)