BIRD MIGRATION by Julie Jansen
Did you know 2018 is the year of the bird?
It is the 100th anniversary of the Migratory bird Treaty Act. The Migratory Bird Treaty Act was signed by the United States and Canada in 1918 for the purpose of ending the commercial trade in feathers. Around the turn of the 20th century, the long breeding plumes on many bird species were highly prized fashion accessories, and thousands of birds were killed for this purpose. The treaty prohibited the hunting, killing, capturing, sale, transportation and exportation of migratory birds, and their feathers, eggs and nests. It also provided for the establishment of refuges to protect bird habitat, and it encouraged the monitoring of bird populations for conservation purposes. Amendments to the initial treaty extended its range to include other nations like and Japan, Mexico and Russia.
Why Do Birds Migrate? Birds migrate to move from areas of low or decreasing resources to areas of high or increasing resources. The two primary resources being sought are food and nesting locations. Birds that nest in the Northern Hemisphere tend to migrate northward in the spring to take advantage of increasing insect populations, budding plants and an abundance of nesting locations. As winter approaches and the availability of insects and other food drops, the birds move south again. Escaping the cold is a motivating factor but many species, including hummingbirds, can withstand freezing temperatures as long as an adequate supply of food is available. How do bird prepare for migration? As days shorten at summer’s end, photoreceptors in their brains trigger hormonal changes that stimulate many birds to molt into new feathers that will stand up to the rigors of a long flight. Their hormones also trigger a huge appetite, and they start eating voraciously, gaining significant amounts of weight. Many insect eating species supplement their diet with fruits, grains, and other items that can be converted to body fat, which birds burn efficiently for energy. These hormonal shifts make birds increasingly restless, especially at nighttime. Suddenly, one day it’s time to go! How Do Birds Find Their Way? Navigation is complicated because it requires that birds know three things: their current location, their destination, and the direction they must take to get their destination. Some birds use the sun and the stars to navigate. Some also use the sighting of landmarks like rivers, mountains or coastlines. Some might use smell, while some might follow other birds in the flock. But birds can still navigate on cloudy days and fly across the ocean where there are no landmarks. So how can they do this? Scientists have come to believe that birds monitor the earth's magnetic field using tiny grains of a mineral called magnetite that are located in their beaks. The iron-containing mineral might act like a compass. Other scientists think that the birds can actually see the magnetic field with their eyes. Not all is known about how birds find their way, but they probably use more than one method. The Arctic Tern has the longest known migration route. It flies about 22,000 miles each year between its breeding grounds in the high Arctic and its winter grounds in the Antarctic.
Hummingbirds are the smallest migrating bird with an average weight of 1/8 of an ounce. They can travel as fast as 30 mph when migrating. Their migratory path takes them across the Gulf of Mexico twice a year, and they fly across the water rather than follow the longer shoreline route. These brave little birds will fly non-stop up to 500 miles to reach U.S. shores. It takes approximately 18-22 hours to complete this amazing solitary flight. Larger birds fly faster than smaller birds. If a flock of birds flies for 10 hours a day, then they can fly about 400 miles a day. Birds on long-distance migrations fly at higher altitudes than those who fly short-distances. Radar studies show that most flight occurs at less than 10,000 feet, but bar-headed geese have been recorded flying as high as 27,000 feet across the Himalayas in order to migrate! Migration can be extremely dangerous for birds, and many don’t often make it back to their starting point. Sometimes natural occurrences like harsh weather play a role, but many times, human activities are the cause of birds’ untimely demise. In the United States alone, up to one billion birds die each year from window collisions. And approximately seven million die from striking TV and radio towers in North America annually. Have you ever wondered what time of day birds migrate? When most of us are making our morning and afternoon commutes to and from work, migrating birds are feeding and resting. Many birds migrate during the night. They do this for a variety of reasons. At night, the air is cooler which eliminates the need to stop as much to cool down. Also, at night there are fewer predators and visibility of these predators is low. Birds are safer traveling when their predators are resting. However, this is not the case for all birds, as you typically see geese and cranes migrate during the day. Migration is a grueling and risky endeavor — birds lose a major chunk of their body weight along the journey, and many of them die. A successful journey relies on there being key stopping points along the route so the birds can rest and refuel. Migration is like a chain, with each stopping point forming a connecting link. But as humans continue encroaching on the natural environment, they break individual links and increase the risk that the fragile chain of migration will break. If the decline in migrating bird species is to be stopped, then nations around the world must cooperate more effectively across their borders to map out adequate protections for migratory birds. How You Can help, here are some steps… Creating bird-friendly landscaping and preserving natural habitats for birds to rest and refuel during migration. This includes choosing native plants and providing water to birds as well as offering good food both naturally and through supplemental feeders. Keeping bird feeders and bird baths clean and fresh to avoid spreading diseases that could infect migrating birds and thus spread to migratory flocks. Using several methods to prevent bird window collisions at home, and supporting “lights out” campaigns in local cities where office buildings can be a hazard to migrating birds.
Minimizing or avoiding pesticide use and taking care to dispose of oil, lead and other toxic materials safely and responsibly so there is no environmental contamination that can affect birds. Taking steps to discourage feral cats and always keeping pet cats indoors so they do not threaten birds. Dogs should always be closely supervised and leashed when near popular bird habitats as well. Supporting strong enforcement of local hunting laws and measures to prevent poaching or illegal hunting activities. And last but not least…Sharing your love of birds with friends and family members to introduce them to this rewarding hobby. This helps raise awareness of birds in every season and encourages more people to enjoy migration and protect migrating birds.