A Short Flight Into the World of Migration
Now that the mornings are cooler, the leaves are browning and falling to the ground, and the daylight hours are dwindling, we know that it is time for some changes. We may go to the basement, or to the highest shelf in our closet and pull out our warm coats, thick scarves, and knitted gloves. All of this is preparation for what’s to come: winter. While all of this hustle and bustle is happening inside of our homes, the animals outside our windows are preparing for the changes as well.
Many birds, that just a few months prior, were singing gleefully for a mate, are now preparing for a long journey to a warmer wintering ground -- they are going to migrate. Birds will undergo a few physical changes before they take off on their flighted trek, making sure they are primed for the next few months. One important (and very energetically costly) make-over is the molting their worn out feathers, a process that occurs between breeding and migration when food is still abundant. This means that each bird will slowly shed its frailed feathers and grow new, intact ones which will keep the bird in the best possible condition for flying.
Migrating birds will also ensure they are energetically prepared for the journey by becoming voracious eaters and gaining up to two times their summer weight. This extra fat will allow the bird to fly for a long time without having to stop for food as often as they otherwise would. Then, shortly before a bird begins to migrate, they become very restless due to hormonal changes triggered by shortening days and the dwindling food supply. This anxious behavior is known as Zugunruhe, a German word made up of the parts “Zug” meaning move/migration and “Unruhe” meaning anxiety/restlessness. The main behavior associated with zugunruhe is an increased urge to fly, making it more and more difficult for the bird to rest, until the urge is so strong, and migration begins.
There are a few types of migration in birds: short distance (can be moving to lower elevation on a mountain), medium distance (moving distances equivalent of a few states), and long-distance (traveling across continents). Birds that have long-distance migration paths will utilize stopover sites in order to rest, re-fuel their bodies, and find shelter from any dangers (such as storms). Interestingly, most species will perform their migratory flights during the night, as a way to avoid exhaustion from the heat as well as predators. So, if you were to go out at night during migratory months, you may be able to hear flocks passing by overhead (particularly Canada Geese with their loud honks). They are able to find their way in the dark because they are following the magnetic pull of the earth, as well as the orientation of the stars, rather than visualizing their geographical path.
The lengths of some migrations are truly incredible: the North American Arctic Tern steals the show with a yearly migration distance of 24,000 miles, which, over its 30 year lifespan, can add up to the equivalent of 3 trips to the moon and back! Unfortunately, not all birds will complete the full journey, as some are lost to building/window strikes, predation by feral cats, and illegal hunting while some perish from exhaustion, or disease (as a result of being in close quarters with other individuals). Also, due to habitat destruction by humans, many birds are losing important stopover sites and are unable to survive their full trip.
But don’t worry, just because birds are beginning to migrate does not mean that you will not see your feathered friends anymore! Many species are year-round residents (ex: Northern Cardinal, Blue Jay), and some species will even be coming to Maryland as their wintering ground (ex: Dark-eyed Junco, White-throated Sparrow). So be sure to keep your eyes and ears peeled for flocks of migrating birds, as well as our winter/year-round residents!
Cover Image: Public Domain Photo by Artur Rydzewski
Second Image: Public domain photo by Simon Pierre Barrette on Wikimedia Commons
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