The Awe and Mystery of Bird Migration
Bird Migration is One of Nature’s Most Amazing Phenomena!
Approximately half of the world’s nearly 10,000 known bird species migrate.
Many birds travel every year from the Northern Hemisphere to the Southern Hemisphere and back in search of food and breeding grounds. But how do seasonal migrants—and other birds, such as seabirds that make long ocean feeding journeys—navigate this amazing journey?
There are many different species of birds that seem to hatch with genetic programming that gives them a basic framework of where to go as the seasons change. Even more astonishing, many make their first migration without the help of their parents! Because they modify their routes based on experience, they rely on a combination of different techniques to navigate.
One of the easiest ways a bird can make sure it’s on the right track when flying on a clear day—is to look for familiar landmarks below. Bird migration is aided by familiar sights and smells. Some ornithologists believe that day-migrating birds pay attention to features such as rivers and mountains and use them to plot their routes. There is even evidence that nocturnal migratory birds can fine-tune their routes based on rivers when they are close to their destination.
But what about birds that have no landmarks to navigate? For example, seabirds sometimes fly long distances over an almost featureless ocean. The nose knows. One remarkable answer is that some birds can follow their nose.
In a 2017 study, researchers temporarily disabled the sense of smell in a group of Scopoli’s Shearwaters by washing their nasal passages with an otherwise harmless chemical called zinc sulfate. They then tracked the birds with GPS devices as they foraged near the Spanish coast, comparing them to the puffin they still smelled. The test team continued to navigate efficiently on land, but as they went out to sea they became confused, suggesting that scents fill in the gaps when landmarks are not available.
Migratory Birds Are Guided By the Sun and Stars
Not all birds have a good sense of smell – and if you travel at night (as many songbirds do), landmarks may not be very helpful. When this is the case, birds rely on sky navigation.
In the 1960s, a father-son team studying bird migration, John and Stephen Emlen, devised a clever method to investigate whether birds used stars to navigate. They placed captive birds with seasonal “migratory restlessness” in small cages with ink pads at the bottom and lined the cages with paper funnels they called Emlen funnels. As the captive birds struggled to take flight, their feet left inky marks on the paper-covered sides of the cage. To test whether the birds chose their direction based on the stars above, the Emlens placed the caged Indigo Buntings in a planetarium where they could manipulate the positions of the celestial bodies. When they turned the “sky” of the planetarium so that the “north” appeared in another direction, the birds changed their direction accordingly, indicated by the traces of their feet in the funnels – aligning themselves according to the stars.
Many studies have shown that birds use the rising and setting sun as important cues for finding direction. For example, a 2001 study tracked the changing flight paths of shorebirds south of the Arctic using radar and found that the only way to explain certain features of the routes was to assume they were following a “sun compass” and changed course. slightly because their internal clocks lost sync with local time during long journeys.
Birds Using Magnetic Fields and Quantum Physics
It’s not hard to imagine finding your way by following a river, the North Star, or even your nose. After all, we humans share our senses of sight and smell with birds. But bird migration also seems to rely on a sixth sense that we lack: the ability to sense the earth’s magnetic field.
Experiments dating back to the 1960s to test this ability by manipulating magnetic fields around birds in the laboratory have shown that birds change direction in response to changes in those fields. The question is how?
Some studies have suggested that the upper parts of bird’s bills, including pigeons, contain tiny particles of the highly magnetic mineral magnetite that help them navigate. Although this theory offers a possible answer, it remains controversial. Magnetite was later found elsewhere in pigeon’s bodies that don’t seem to match as magnetic sensors. Similarly, there are conflicting results from studies that have attempted to anesthetize areas containing magnetite to determine the effects on birds.
An alternative hypothesis has emerged in recent years. This suggests that specific proteins in the eyes of birds can perceive the direction of magnetic fields of the Earth through effects best explained by quantum mechanics. Experiments have shown that birds, depending on light, can detect a magnetic field. It now appears that process may work with blue light-sensitive proteins called cryptochromes.
When a photon of blue light hits the cryptochrome protein in the bird’s eye, a special set of quantum particles called a “radical pair” is created. These are very sensitive to even weak fluctuations in the surrounding magnetic field. The orientation of the magnetic field of the Earth affects the probability that the cryptochrome protein will end up in one of several possible states as a result. The “signal state” of the protein determines what signal is sent to the bird’s brain, and the bird can combine this with other sensory inputs to chart its course. If that’s a little hard to wrap your head around, don’t worry — quantum physics is notoriously confusing.
How You Can Help Migratory Birds
- Keep your cat(s) indoors—birds and cats will benefit. Indoor cats live an average of three to seven times longer. Even well fed cats kill birds and “belling” your cat isn’t always effective.
- Prevent birds from hitting your windows by using a variety of treatments to the glass on your home.
- Eliminate pesticide use in your yard. This is best for birds and the insects they depend on.
- Create backyard habitat by planting native grasses, flowers, and shrubs that attract native birds. Not only will you enjoy more birds but you will have fewer insect pests as a result.
- Reduce your carbon footprint. Swap your gas powered mower for an electric one. If feasible, carpool, use low energy bulbs and Energy Star appliances.
- Contact your energy supplier and inquire if you can purchase your energy from renewable sources.
- Buy organic food and drink shade-grown coffee. Shade coffee plantations maintain large trees that provide essential habitat for wintering songbirds.
- Keep feeders and bird baths clean to avoid disease and prevent mosquitoes from breeding.
- Support bird friendly legislation such as the Migratory Bird Act both locally and in the U.S. Congress.
- Learn more about birds and support important conservation work. Join a local bird conservation or birding group.
Regardless of how birds find their way – through landmarks, scent, the sun and stars, or a mysterious ability to sense magnetic fields based on quantum physics – their journeys are inspiring. And to do them year after year, they need our help. From the United States and Canada, 2.9 billion adult birds have disappeared from every ecosystem in less than one human lifetime. Many of these deaths are a result of the dangers of migration such as building impacts and destruction and loss of natural habitats leading to starvation.
Click here to follow bird migrations using BirdCast’s Migration Dashboard.
Source: How Do Birds Navigate During Migration?
Ross A. Feldner, RCC Board Member
Ross Feldner is the lead, with Bob Musil, of the RCC Bird Watch and Wonder Program. Ross is a life-long birder and photographer who is the editor of the Friends of Patuxent National Wildlife Refuge newsletter. Ross also serves as a guide at the Patuxent National Wildlife Refuge, a frequent birding spot for Rachel Carson who first learned about the health effects of DDT at the laboratory there. He is also the owner/art director of New Age Graphics, a full-service graphic design firm in Wheaton, MD.
