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Celestial
Celestial cues have been linked to navigation in animals and people for hundreds of years. After all, we did measure longitudinal lines by using the stars and sun as reference points. It’s natural to assume birds use celestial cues like the sun and the stars for a reference as well. The sun is thought to be a compass component of the map and compass theory therefore is not debatable. However, the stars and constellations are contested as a primary sense of navigation for nocturnal birds. Scientists claim that birds who fly overnight are able to use the constellations as a directional tool and then navigate in a homeward direction based on the constellations they can see. Some recent evidence with shore birds is suggesting differently. In Averett’s article on Gabrielle Nevitt, she reports new findings on the sizes of the olfactory bulbs in nocturnal shore birds compared to normal birds. These nocturnal birds topped the charts with over six hundred olfactory genes while daytime birds only had two hundred. Suggesting stronger senses of smell on nocturnal birds would not help the constellation argument one bit. Even without this recent study on celestial navigation, there are still some vital questions that still need answers. The biggest concern with celestial navigation is the variability of the seasons and weather. Why would a primary sense be so dependent upon a condition that varies so much? It is also never clear how birds have these constellations and sun movements memorized. It is hard to understand whether birds inherently know the constellations or learn them. This is a big fault on the celestial understanding. If we do not how they are able to have such a sense, it is much harder for us to believe it even exists.
The scientific community is well aware of other animals having special senses aside from the basic five we humans tend to think of. It has been proven and widely accepted that other animals such as fish, ants, bees, lobsters, newts, turtles, and bats are all able to sense magnetic fields also referred to as magnetoreception. It is only logical for experts to question a bird’s ability to use magnetic senses to navigate.
The scientific community is well aware of other animals having special senses aside from the basic five we humans tend to think of. It has been proven and widely accepted that other animals such as fish, ants, bees, lobsters, newts, turtles, and bats are all able to sense magnetic fields also referred to as magnetoreception. It is only logical for experts to question a bird’s ability to use magnetic senses to navigate.
Magnetoreception
Even among those who believe birds utilize their magnetoreception as a navigational tool, there is still dispute about how the bird senses these magnetic fields and when the bird develops these senses. Some believe the magnetic receptor is in the bird’s beak, while others like to argue that birds can actually see the magnetic fields; that the magnetic receptors lie in their eyes. The most widely accepted idea for magnetorception is that the magnetic fields are sensed throughout the body, more specifically in the nerve cells of the bird. Another highly debated aspect within the magnetoreception spectrum is when a bird develops this sense. Many argue that birds are born with the ability to sense magnetic fields while others like Wiltschko, a German zoologist and ethologist specializing in ornithology, argue that birds develop a “map” as they gain experience migrating (2014). He backs this claim up with a notable study that used strong magnetic pulses on birds of all ages in migration. Each time a pulse was sent it temporarily changed the experienced birds’ orientation by ninety degrees while the juvenile birds continued on their course unaffected. Recent studies over the past ten years have shown time and time again a connection between birds and magnetism. It has become widely accepted that birds have magnetic sense, but not so finite on the tie between magnetic fields and a birds navigational map.
I’m not so convinced that a bird’s magnetoreception is the most efficient option for bird’s to use and I am not the only one who feels this way. Wiltschko discusses the main reason why magnetoreception cannot be a primary navigation tool, “Magnetic intensity could easily be used to detect a north-south displacement, but there is no obvious factor indicating east-west displacements” (Wiltschko 2012). This is the largest discrediting flaw for magnetic senses. Even though birds migrate move north to south it is still important to have the east to west guidance in order to reach an exact location over and over again. How is a bird supposed to navigate primarily on a navigational map that can not even direct them east or west with any accuracy? For this reason, along with lack of evidence proving sufficient change in orientation or behavior of navigation, I rule out the idea of magnetoreception being a primary navigational sense. However, I do consider this sense valuable and necessary for birds to navigate with such I ease and confidently claim that magnetoreception is a secondary and/or complimentary navigational tool for migrating birds. In order to determine what extent this magnetic system is used we will need to wait for newer, more developed technology, improved research techniques, and hard data. Until such evidence arises, I must eliminate this sense as an option for a primary navigation role and encourage others to do the same.
I’m not so convinced that a bird’s magnetoreception is the most efficient option for bird’s to use and I am not the only one who feels this way. Wiltschko discusses the main reason why magnetoreception cannot be a primary navigation tool, “Magnetic intensity could easily be used to detect a north-south displacement, but there is no obvious factor indicating east-west displacements” (Wiltschko 2012). This is the largest discrediting flaw for magnetic senses. Even though birds migrate move north to south it is still important to have the east to west guidance in order to reach an exact location over and over again. How is a bird supposed to navigate primarily on a navigational map that can not even direct them east or west with any accuracy? For this reason, along with lack of evidence proving sufficient change in orientation or behavior of navigation, I rule out the idea of magnetoreception being a primary navigational sense. However, I do consider this sense valuable and necessary for birds to navigate with such I ease and confidently claim that magnetoreception is a secondary and/or complimentary navigational tool for migrating birds. In order to determine what extent this magnetic system is used we will need to wait for newer, more developed technology, improved research techniques, and hard data. Until such evidence arises, I must eliminate this sense as an option for a primary navigation role and encourage others to do the same.
Olfactory
One of the most controversial mapping senses for navigation is the bird’s use of their olfactory senses, or sense of smell. The reason for such controversy with this sense is the mere misunderstanding of the birds’ ability to smell. Up until about fifty years ago nearly all scientists believed birds had extremely underdeveloped olfactory senses and their brains anatomy did not show significant evidence of a significant sense of smell (Averett). The idea that birds have an extraordinary sense of smell that enables them to navigate as far as a couple thousand miles is hard to wrap a mind around when not too long ago we doubted their ability to smell anything at all. Then again, no one believed that the earth was round at first either. Although it is hard for some to accept, we must admit we were wrong and continue researching to better understand this great scientific mystery referred to as bird navigation.
To solve such a mystery we need to identify how the birds use their olfactory senses so well. Most experts who theorize about olfactory navigation agree that birds do so by analyzing trace gases in the atmosphere carried by winds in their olfaction nerves. The big idea is that birds collect and store scents in their memory from every location and are then enabled to build an olfactory scent map that allows them to navigate based on the trace smells of home in the air. In biologists argue that bird’s cannot use this sense to migrate long distances while Floriano Papi, an Italian zoologist and animal behaviorist, has evidence against such assumptions. Papi claims that birds can use their olfactory senses to pick up trace odors that originate over three hundred miles away from the bird’s current location (“Cornell Laboratory,” 2007). This would allow for birds to navigate fairly easily over long distances. Overall, scientists have some great theories as to how birds use their olfactory senses. The biggest issue to overcome is collecting enough data with advancements in technology to disprove those stuck in the past thinking that birds cannot smell. Like they say, old habits die hard.
To solve such a mystery we need to identify how the birds use their olfactory senses so well. Most experts who theorize about olfactory navigation agree that birds do so by analyzing trace gases in the atmosphere carried by winds in their olfaction nerves. The big idea is that birds collect and store scents in their memory from every location and are then enabled to build an olfactory scent map that allows them to navigate based on the trace smells of home in the air. In biologists argue that bird’s cannot use this sense to migrate long distances while Floriano Papi, an Italian zoologist and animal behaviorist, has evidence against such assumptions. Papi claims that birds can use their olfactory senses to pick up trace odors that originate over three hundred miles away from the bird’s current location (“Cornell Laboratory,” 2007). This would allow for birds to navigate fairly easily over long distances. Overall, scientists have some great theories as to how birds use their olfactory senses. The biggest issue to overcome is collecting enough data with advancements in technology to disprove those stuck in the past thinking that birds cannot smell. Like they say, old habits die hard.