Migratory birds have long fascinated scientists. Until fairly recently, the theory was that
special iron-rich nerve cells in the beaks of birds assisted with their extraordinary
navigations skills. Specialists have known for a while that birds, as well as other
animals, can sense the earth’s magnetic field. However, the exact mechanism for this
sense has eluded researchers for a number of years, until now. A recent study has
seemingly identified a protein in the eyes of birds that allow them to see magnetic fields.
In this article, we’ll examine what makes this protein so useful, and how birds use it as
an internal compass.
Robins and Finches
The recent findings were made evident in two papers that were published earlier this
year. The studies each focused on a different species of bird. The first examined robins,
whilst the second looked at zebra finches. Both of these migratory birds show incredibly
precise navigation skills, and the exact mechanism for this has been a subject of much
research. The two studies found that proteins in the birds’ eyes, known as Cry4, are
particularly sensitive to blue light.
Cry4 is what’s called a cryptochrome, a particular type of protein found in cells that are
sensitive to light (photoreceptor cells). These cryptochromes themselves are fairly well
studied, as they’re found in both birds and mammals. They help to control our circadian
rhythm or internal body clock. Yet evidence in recent years has shown that birds use
these cryptochromes to orient themselves. This sense, known as magnetoreception,
allows birds to detect magnetic fields.
Blue Light
Cryptochromes are sensitive to blue light. Studies in birds suggest that it’s only possible
for birds to use their magnetoreception to navigate in the presence of blue light. Blue
light has a short wavelength, meaning that it has a relatively high amount of energy
compared to other visible light. We’re all familiar with ultraviolet or UV light. It’s the part
of the light spectrum that can cause sunburns and potentially skin cancer. Blue light is
slightly less powerful than UV light. In humans, Blue light can contribute to digital eye
strain. However, thanks to birds’ Cry4 proteins, they can use this part of the spectrum to
navigate using the earth’s magnetic field.
The Studies
As mentioned above, there were two separate studies that focused on this magnetic
compass in birds. The first was by a team of biologists and researchers from Lund
University in Sweden. This team examined zebra finches to discover how the different
cryptochromes in their brains, muscles, and eyes reacted. Because these proteins are
linked to the circadian rhythm, they expected to see some fluctuation in key areas.
However, they also believed that one of the proteins would stay comparatively more
constant. Sure enough, Cry1 and Cry2 proteins fluctuated throughout the day, but Cry4
stayed at a constant level. This indicated that it was used in magnetoreception.
The second study was conducted by researchers at the Carl von Ossietzky University
Oldenburg in Germany. They examined migratory European robins in a similar way.
Their findings supported that of the zebra finches study, but filled in even more pieces of
the puzzle. They found that the key protein was clustered around a region of the birds’
eyes that received a lot of light. This was particularly true during migration season.
These findings give further evidence to theory that these birds can actually see the
magnetic field of the earth in certain light conditions.
Although the evidence from both of these studies is compelling, the researchers
involved have noted that further examination is definitely needed. Although in these two
studies it seems that Cry4 is the protein responsible, there have been other studies that
suggest the Cry1 or Cry2 proteins could in fact be responsible. Regardless, both studies
have gone a long way to progressing our understanding of how certain species see the
world. Further studies examining the absence of the Cry4 protein could help scientists
understand this matter further.
What Do Birds See?
It’s obviously impossible for us to know exactly how another species sees the world. But
based on the data available, scientists can make an educated guess. Some researchers
have suggested that birds may have a filter over their field of view. This filter may
appear like a dark aura that fluctuates depending on the light conditions they are in.
Numerous studies have been carried out in the past on birds’ sight, with the conclusion
being that many species use both visible and UV light to see. Research suggests that
UV signals play a major role in the various habits of birds. For example, the UV
spectrum could play a part in choosing a mate, finding food, and receiving signals from
hungry chicks. It’s clear that the way birds see the world is a complex and intriguing
matter.
A Magnetic Compass
From the two most recent studies into how birds navigate, as well as the body of
research that has been built over the last decade, it’s clear that magnetic fields play a
considerable role in their navigation. Research into how cryptochromes are affected by
blue light has been crucial to determining how this process works. Although it can’t be
said with full certainty which of the proteins is responsible for birds’ magnetoreception,
the most recent studies have suggested Cry4 is the most important one.
Discovering exactly how birds see and navigate gives us insight into how they live their
lives and a better understanding of nature as a whole. Migratory patterns, relationships,
and other behaviours are seemingly all influenced by their unique vision. This knowledge
also allows us to better protect these species. Further research is needed to know with
certainty how their sight actually works, but the latest research has brought us a big
step closer toward a total comprehension of birds’ incredible natural ability to navigate so
accurately, and precisely how.
Could Humans Recreate Birds’ Natural Visual Abilities?
Imagine if humans could reproduce this incredible ability and harness its practicality.
Not only would viewing magnetic fields in real-time be incredibly useful for
understanding our planet, it would be an amazing sight to witness with your own
eyes—like the majestic Northern Lights. Who knows what the future of biotechnology
holds and what sort of genetic modifications might become commonplace in certain
professions?
