NAME: KPODO GODWIN YAO SETSOAFIA INDEX NUMBER: UEB3707618 COURSE: ANIMAL BEHAVIOUR ASSIGNMENT 1 BIRDS In 1951 Gustav Kramer discovered the sun compass. He performed his experiments by placing European Starlings in orientation cages and then used mirrors to shift the apparent location of the sun. In response, the birds shifted their migratory restlessness to match the compass direction indicated by the apparent new position of the sun. Further research revealed that the bird’s sun compass is tied to its circadian rhythm. It seems birds have a time compensation ability to make allowances for changes in the sun’s position over the course of the day. This theory is supported by another experiment in which pigeons were placed in a closed room with an altered cycle of light and dark. Over a period of a few days, their circadian rhythm was reset. The birds were then released on a sunny day. Because their “internal clock” had been reset, they misinterpreted the position of the sun and made a predictable error in their homing direction. The pigeons actually ignore the position of the sun relative to its position in the sky, relying on its azimuth direction, i.e., the compass direction at which a vertical line from the sun intersects the horizon. Further study has also revealed that pigeons have to learn the sun’s path to use it in navigation. Young pigeons allowed to see the sun only in the morning lack the ability to use the sun for navigation in the afternoon. Birds can determine the compass direction from the sun (or from sun-related cues like the skylight polarization pattern) by compensating, through their circadian clock sense, for the sun’s apparent daily movement in azimuth. One possibility, aside from the escape response documented here, is that the sun plays a similar role in homing and migratory behavior as it does in birds. Birds use geomagnetic cues during migration over long distances, where the sun’s arc (and the compensation schedule) would constantly change, but use a sun compass for orientation over shorter distances, such as the directed movement within a familiar home range where the azimuthal changes over the course of a day can be learned. Wiltschko and Wiltschko (2009) hypothesize that many birds actually learn two compensatory schedules for changes in the sun azimuth: one for foraging and/or breeding sites in the temperate zone, and another for overwintering areas in the tropics. This hypothesis may also apply to both terrestrial and marine turtles that for at least some extended periods occupy familiar home ranges (Makowski et al., 2006). Birds migrating by day use the Sun to navigate, adjusting their angle to the Sun as the Sun’s position moves from east to west. Some birds, like robins, use Earth’s magnetic field to assist in migration. It is believed that they have magnetic crystals near their nostrils to help them sense the field and orient themselves. Birds also use landmarks such as islands, trees, and buildings, as well as sounds and smells, when they search for nesting grounds in spring. MONARCH BUTTERFLIES Monarch butterflies navigate by a sun compass, meaning they use the position of the sun to determine which way is south. Monarch butterflies use the Earth’s magnetic field and a ‘sun compass’ in their antenna as navigational tools for their long-distance migration, scientists say. Monarchs use a time-compensated sun compass in their antenna to help them make their longdistance migratory journey to overwintering sites. Monarchs use a light-dependent inclination magnetic compass to help them orient southward during migration. Monarch butterflies have a keen sense of direction, even on cloudy days. This is because they have a magnetic compass to direct their migration in addition to navigating by the position of the sun. The magnetic compass was ultraviolet light-sensitive and an essential orientation mechanism to aid migration when directional daylight cues are unavailable. The monarchs are using the sun as a celestial cue. Since monarchs migrate during the day, the sun is the celestial cue most likely to be useful in pointing the way to the overwintering sites. This proposed mechanism is called a sun compass. Monarchs may use the angle of the sun along the horizon in combination with an internal body clock (like a circadian rhythm) to maintain a southwesterly flight path. The way this would work is illustrated below. For example, if a monarch’s internal clock reads 10:00 AM, then the monarch will fly to the west of the sun to maintain a southern flight direction. When the monarch’s internal clock reads noon (12:00 PM), the monarch’s instincts tell it to fly straight toward the sun, while later in the day the monarch’s instincts tell it to fly to the east of the sun. Scientists have suggested that monarchs may use a magnetic compass to orient, possibly in addition to a sun compass or as a “back-up” orientation guide on cloudy days when they cannot see the sun. Studies of migratory birds have indicated that they register the angle made by the earth’s magnetic field and the surface of the earth. These angles point south in the Northern Hemisphere and north in the Southern Hemisphere. Migratory monarchs indeed possess a magnetic compass that aids in orienting migrants south towards their overwintering grounds during fall migration. Remarkably, the use of the magnetic compass requires short wave UV-light (previous magnetic compass experiments failed to account for light at this range). With UV-light being allowed to enter the flight simulator, eastern migratory monarchs consistently oriented themselves south. The light-sensitive magneto sensors reside in the adult monarch’s antennae. While the expert consensus remains that the sun compass is the monarch’s primary compass for navigation. HONEY BEES Honey bees use the sun as a reference point in navigation and communication. Experiments have shown that bees have an internal representation of the sun's movement through the sky and suggest that this representation is innate, but is tailored by experience. Research into this pattern shows that the bees navigate relative to the sun. Since the sun is so far from the earth, over a short time, the bee cannot see the sun's motion, even if the bee moves. (Humans often see a similar effect when driving; distant objects seem to move less than the signs near the road.) The bee can, therefore, use the sun as a fixed point and orient itself by maintaining a fixed angle between its line of flight and the line to the sun. The sun, however, plays a greater role in the food gathering cycle. The dance language, which bees use to communicate, is also based on the location of the sun. When bees return from a food source, they perform a ``waggle dance'' on the vertical comb nearest the entrance to the hive. The dancing bee makes a short, straight run while waggling its abdomen, then circles back and repeats the action several times. The bee orients its dance so that the angle between the direction of the straight run and the ray opposite gravity is the same as the angle between the food source and the position of the sun. In this scheme, dancing straight-up means ``fly toward the sun,'' and dancing straight down means ``fly away from the sun.'' Given this angle, other bees can orient themselves to the sun and locate the food source. The bee, having some innate sense of the sun's movement, flies out to search for food. She has probably flown a few times before and has refined her sense to great precision. When she finds food, she returns straight home, and, because she has a sense of the sun's direction, she will be able to dance at the proper angle to tell the other bees where to fly. Since they too know where the sun is, even though they may not be able to see it due to cloud cover, they are able to navigate to the food source. Honey bees have the ability to detect the Earth’s magnetic field and the suspected magnetoreceptors are the iron granules in the abdomens of the bees.
