Navigation in birds

Dedicated to all Zoologists

1. Navigation in birds By Saleem ullah Reg : zo220172044 Submitted to : MAM IRUM GUL Department of Zoology Kohat University of Science and Technology, Kohat-26000 Khyber Pakhtunkhwa, Pakistan

2. Birds are not perfectly adapted to all environments and sometimes a bird has to leave – migration. In its purest sense, migration refers to seasonal movements between a location where an individual or population breeds and a location where it survives during the non breeding period. Long-distance migrants are those that have a complete shift between the breeding and wintering areas, such as the Blackpoll Warbler that breeds in Canada; short-distance migrants, such as the Pine Warbler, make shorter trips, such as up and down the side of a mountain .

3. A migratory journey is usually broken into a series of short flights. Most songbirds migrate at night, singly or in loose flocks, and my cover 300-600km per night but they don’t fly every night and a 3000 km journey may take 3-4 weeks. Birds might also have more than two migratory destinations. Anna’s Hummingbird, for example, breeds in the coastal chaparral and valley of California, summers in the high mountains, and winters in the deserts of Arizona and Mexico. Birds tend to migrate along four major routes in North America called flyways, depicted below.

4. Banding Recaptures of banded birds give us a lot of information as to where birds go and how long they live, but only a small % of banded birds are ever recovered. About 25% of banded ducks and geese are recovered because they are hunted, but fewer than .1% of songbirds are recovered. But even when a bird is recovered, we only know where it was banded and where it was recovered and how long it was in-between – not where the bird was in the meantime or how long it took it to get there.

5. Food Habits and Migration There is often a relationship between food habits and migration. Insects become scarce in the winter in northern latitudes, so insectivorous birds must move closer to the equator where insects are more abundant. Insectivorous birds are the largest group of migrants. Some insect-eaters, such as chickadees, can eat seeds in the winter and thus do not tend to migrate. Fruit-eating birds may not have to migrate as far because fruits are generally available at the edge of the temperate zone

6. Geography and Migratory Behavior There is more land area in the north temperate zone than there is in either the tropics or the south temperate zone; i.e. there is more potential breeding area than wintering area. There is even more contrast in habitat types; e.g. in the New World, the total amount of tropical forest in South and Central America is about equal to the total amount of forest in North America. But there is a limited amount of other habitat types in both areas.

7. Site Fidelity If a bird returns to the same site each year, it must have some sort of genetically-based ability to remember the site and how to get there. For example, a young warbler may carry genetic information that causes it to remember its place of birth and then respond to cues that guide it to Puerto Rico. The young bird then spends the winter moving around, searching for a good place to stay. After overwintering, it returns north to the area of its hatching. The next year it returns to the same site in Puerto Rico. So the bird may spend its life in only a few hectares in two sites thousands of miles apart.

8. Route Selection Evolution of a migratory route is determined by many factors. Geographic or topographic factors are important for some species. But even some small warblers and hummingbirds have the ability to fly across the Atlantic Ocean on their way from North America to Mexico. But other species, such as some hawks and Turkey Vultures, follow the land route rather than crossing the ocean . Obviously , migratory routes have changed a great deal over geologic time; the glaciers of the ice ages advancing and retreating must have forced birds to change their routes, so migratory routes must have evolved like any other behavior to changing conditions.

9. Navigation and Orientation How does a bird find its way? We can learn some things about the navigation and orientation behavior of birds through observation or through banding, but the best information has come through experiments. Species vary in their navigational abilities. Some birds have the ability to find their way back if they are displaced. Homing pigeons are pretty good at this and the most impressive was a Manx Shearwater, taken from its burrow on the Atlantic coast and flown to England by commercial aircraft, returned to the burrow in 12.5 days.

10. Most early studies on navigation tried to explain it by one mechanism. But now we know that birds use several mechanisms. Landmarks Solar Cues Stellar Cues Geomagnetic Cues etc .