Nature Notes: Birds on the Move.
By Menna Megahed
Every fall for the past couple of years I've waited patiently for the arrival of a special visitor. All the way from Europe comes a small monochromatic bird with a distinctive stride, the White Wagtail. As its name suggests, a striking feature of the bird is its long, constantly wagging tail. I spent so much time chasing that little bird around the gardens of the American University in Cairo just to see it run; I always felt like Wile E. Coyote chasing around the Road Runner!
Another visitor I look forward to seeing in the spring is the European Bee-eater, a beautiful bird with brilliant colors. The blend of turquoise, yellow and brown on its slender build is simply breathtaking. You're more likely to hear it before you actually see it, though, a soft kruu kruu is what draws your eyes to the sky. You'll see a graceful bird gliding by with its kite-shaped wings and orange underwings. Last spring was my first time seeing a male Common Redstart, a small bird that is barely noticeable if it weren't for its bright orange underparts and black throat. All these birds are migratory birds, they travel great distances for various reasons. How do they make their incredible journeys is a question scientists have been trying to answer.
Over the years, scientists have discovered many strategies used by migratory birds. The most famous is the V-formation used by waterfowls. Birds that travel in formation are able to save a lot of energy by synchronizing their wing beats to make use of eddies created by the bird in front. Other large birds such as vultures take advantage of thermals rising from the ground. These birds are able to gain altitude by simply soaring into the rising hot air and travel a larger distance without the need to flap their wings.
The more incredible journeys are made by smaller birds. A paper published in March by William DeLuca shows how scientists were able to follow the 1,500 mile journey of the 13g Blackpoll Warbler from North America and Canada to Puerto Rico and Cuba and then onwards to South America. It was found that this tiny bird is able to fly nonstop for two to three days! But how? For most migratory birds, fatter means fitter. Birds that fly nonstop go on a feeding frenzy before it's time for migration and put on as much weight as possible, some put on more than double their weight. One might think that being heavier is a disadvantage but fat is a great source of energy compared to proteins. Furthermore, birds are able to change the size of their internal organs; they can shrink the organs they don't use during their travels such as the liver and stomach, and increase the size of their flight muscles and heart.
But when do birds know when to pack up their fat reserves and leave? There are many possible answers to this question and all are applicable. The most obvious answer is food. With the arrival of winter in their northern breeding grounds, there is a decrease in available resources and therefore the birds decide to leave the area. Some scientists argue that the main cue for migration is the change in the length of the day. The long summer days provide more time for birds to feed their young; shorter days therefore signal harsher conditions. In the end, they are all environmental cues.
There are studies, on the other hand, that show that migration is genetic. Scientist Herbert Biebach published a paper a long time ago on European Robins and showed that there is a genetic component to why birds migrate. The European Robin is said to be partially migratory, which means that some individuals are migratory but others are not. Biebach was able to study the behavior of offspring from migratory and resident parents. He found that a large percentage of the offspring exhibited Zugunruhe (Zug is German for 'move' and Unruhe means 'anxiety' or 'restlessness.' The term is used to describe the anxious behavior in migratory animals) from migratory as well as resident parents. Whether migration is genetic or environmental, it is still an amazing phenomenon to study.
Unfortunately, not all birds are able to make the journey. Even with good fat reserves, many birds do not survive the flight. The four- to five-hour drive to the North Coast is exhausting for us; imagine flying two to three days nonstop! Exhaustion makes birds less wary of potential threats and they are thus more likely to collide with obstacles. Disease outbreak and natural disasters such as storms, hurricanes and wildfires are also threats to migratory birds. Important stopover sites can be destroyed and birds cannot stop and refuel. Birds that are caught in storms can suffer from injury or even death. One would think that with all these hazards it would be better for birds to just endure a harsh winter rather than cross seas and oceans and possibly die on the way but in actuality, the advantages of migration outweigh the risks. That said, the costs of migration for birds these days are rising due to increased anthropogenic threats.
Egypt, though a wintering ground for many migratory birds traveling south from Europe, is not a happy place to be. Imagine you are a tiny warbler crossing the Mediterranean, you barely have enough energy to complete the journey when there it is: the first sign of land, perhaps in days! You can almost feel the ground beneath your feet as you swoop down toward terra firma. Exhausted from the journey, you do not notice the huge net across the shore. Suddenly you find yourself being sold in a market or being plucked and prepared for a good roasting! Sadly, millions meet this fate with a great number of birds are caught or shot to be sold or eaten, regardless of size, species, or conservation status each year during migration season across Mediterranean shores. Even though some of Egypt's coast is protected, huge nets are set up to capture migrating birds. According to a 2013 National Geographic article, people are noticing the decreasing number of birds arriving but that doesn't stop them. The problem is people just do not realize they might be the cause of this decrease.
On a slightly happier note, there are two species of snakes, the Saharan Sand Snake and the Horned Viper, found in Egypt that thrive on migratory birds. The Saharan Sand Snake is a fairly large slender snake, with a light brown stripe across the eye extending to the snout. The Horned Viper is also quite large but with a shorter, bulkier body. It has a sandy colored body with large brown rounded or squared spots creating a pattern along its back. These snakes are found in the most remote areas of Egypt's deserts -- an environment that is completely barren, with no vegetation whatsoever -- waiting patiently for the arrival of migratory birds for the nutrition the snakes need to survive. So as excited birdwatchers are waiting for the arrival of beautiful migratory birds in the fall, these snakes are waiting for their second meal of the year.
This article was originally submitted as a paper for Dr. Richard Hoath's Travel Writing Class (RHET 3130-01) at AUC.
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