How do migratory birds navigate with such accuracy?

A team of biologists led by the University of Oldenburg in Germany has recently made significant strides in understanding how migratory birds navigate with remarkable accuracy. 

The research, which also included experts from the Institute of Avian Research “Vogelwarte Helgoland”, was focused on the role of a specific protein in birds’ eyes, believed to be a key magnetoreceptor enabling this navigation. 

Genetic basis of how birds navigate 

The researchers compared the genomes of several hundred bird species and observed notable evolutionary changes in the gene encoding the protein cryptochrome 4. They found that certain groups of birds have completely lost this gene. 

“This suggests that the protein is important for adaptation to specific environmental conditions,” said senior author Miriam Liedvogel, the director of the Institute of Avian Research. “A similar pattern has been observed in other sensory proteins such as light-sensitive pigments in the eye.”

Magnetoreception in birds

Previous research revealed that magnetoreception in birds is linked to a complex quantum mechanical process in the retina.

For instance, a 2021 study suggested cryptochrome 4 as the probable magnetoreceptor, showing that it is present in the retina and responds to magnetic fields with a quantum effect, an ability more pronounced in robins than in non-migratory birds like chickens and pigeons.

“Consequently, the reason why cryptochrome 4 is more sensitive in robins than in chickens and pigeons must be found in the protein’s DNA sequence,” explained lead author Corinna Langebrake, a researcher at the Institute of Avian Research. “The sequence was probably optimized by evolutionary processes in these nocturnal migratory birds.”

The role of cryptochrome 4

In the current study, the team examined the cryptochrome 4 genes across 363 bird species, from the little spotted kiwi to the song sparrow. 

They compared the evolutionary rate of cryptochrome 4 with that of other related proteins and found that while other cryptochromes have changed little over time due to their crucial role in regulating the internal clock, cryptochrome 4 showed high variability. This variability suggests a specialized function, potentially as a magnetoreceptor. 

“A similar pattern has been observed in other sensory proteins such as light-sensitive pigments in the eye,” Liedvogel said. Particularly among passerine birds, the protein appears to have undergone rapid selection, further supporting its specialized role in magnetoreception.

Alternative mechanisms of magnetoreception

Interestingly, the study also found that three clades of tropical birds – parrots, hummingbirds, and Tyranni (suboscines), known as tyrants – have lost the gene for cryptochrome 4, indicating it may not be essential for their survival. 

Since some tyrants are long-distance migrants, their lack of cryptochrome 4 presents an opportunity to explore alternative mechanisms of magnetoreception.

Do some birds navigate without any magnetic sense?

“The fact that, unlike robins, they do not have cryptochrome 4 makes them an ideal system for investigating various hypotheses about magnetoreception,” Langebrake explained. 

A key question is whether the Tyranni have evolved a magnetic sense that functions without the cryptochrome 4 protein, or if they can navigate without relying on any magnetic sense at all. 

Additionally, it’s possible that their magnetic sensing capabilities mirror those found in robins, which rely on light and can be influenced by external factors such as radio waves.

“The first two scenarios would strongly corroborate the cryptochrome 4 hypothesis, while the third would pose a problem for the theory,” she added.

Magnetoreception and bird navigation 

Moving forward, the research team plans to investigate magnetic orientation in Tyranni to better understand the function of cryptochrome 4 and its importance in magnetoreception among migratory birds. 

This research not only deepens our understanding of avian navigation but also opens new avenues for exploring evolutionary adaptations in sensory perception.

More about how birds navigate 

Migratory birds have remarkable abilities to navigate across vast distances, often traveling thousands of miles between breeding and wintering grounds. Their navigation skills are attributed to a variety of mechanisms:

Sun compass

Birds use the sun as a compass. They can gauge the time of day and adjust their flight direction based on the sun’s position in the sky.

Star compass

During night migration, many birds use the stars to navigate. They can identify constellations and use them to maintain their flight path.

Geomagnetic field

Birds are sensitive to Earth’s geomagnetic field. They have magnetoreceptors that allow them to sense magnetic fields, which helps them determine their latitude and longitude for orientation.

Polarized light patterns

Birds can detect polarized light patterns in the sky, which are most prominent at sunrise and sunset. These patterns can help calibrate their internal compasses.

Landmarks

For birds that fly at lower altitudes, physical landmarks like rivers, mountains, and coastlines can serve as guides.

Olfactory cues

Some research suggests that certain birds may also use olfactory cues – smelling their way along their migration routes.

The study is published in the journal Proceedings of the Royal Society B: Biological Sciences.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–