White-tailed eagles, also known as Haliaeetus albicilla, have excellent vision during the day, but their ability to see at night is limited compared to some other bird species. As diurnal birds, they are most active and rely on their vision during the day.
The Visual Capabilities of White-Tailed Eagles
White-tailed eagles have a wide visual field of about 110 degrees, which is broader than the human visual field of around 100 degrees. Their eyes are similar in size to human eyes, but they are positioned on the sides of their heads, giving them a more comprehensive view of their surroundings. This wide visual field helps them spot prey from a distance.
The eyes of white-tailed eagles are adapted for bright light conditions. They have a high density of light-sensitive rods and cones in their retinas, allowing them to see clearly in bright sunlight. They also have a reflective layer at the back of their eyes, called the tapetum lucidum, which reflects light back through the retina, increasing their sensitivity to light.
Night Vision Limitations
Image source: white tailed eagle by Andreas Weith
Despite their excellent daytime vision, white-tailed eagles do not have the same level of night vision as some other bird species, such as owls. Their pupils are round, unlike the vertical slit pupils of nocturnal birds, which are better adapted for low light conditions. White-tailed eagles also have a lower density of rods in their retinas than nocturnal birds, which means they are less sensitive to light in low light conditions.
Hunting Behavior
While white-tailed eagles have limited night vision, they are still able to hunt at dawn and dusk, when light levels are lower. They primarily feed on fish and birds, which are more active during the day, but they will also take small mammals and carrion.
Adaptations for Daytime Hunting
White-tailed eagles have several adaptations that make them well-suited for daytime hunting:
| Adaptation | Benefit |
|---|---|
| Wide visual field | Allows them to spot prey from a distance |
| High density of light-sensitive rods and cones | Enables clear vision in bright sunlight |
| Reflective tapetum lucidum | Increases light sensitivity |
These adaptations help white-tailed eagles to effectively hunt and thrive during the day, but their limited night vision means they are less active and successful at hunting during the night.
Conclusion
In summary, while white-tailed eagles have excellent vision during the day, their ability to see at night is limited compared to some other bird species. They are diurnal birds, with a wide visual field and high density of light-sensitive rods and cones in their retinas, which allows them to see clearly in bright light conditions. However, their round pupils and lower density of rods in their retinas mean they are less sensitive to light in low light conditions, limiting their night vision capabilities.
References:
– Canon Pro Stories: Markus Varesvuo – Eagles
– White-tailed Eagle – Forestry and Land Scotland
– White-tailed Eagle – Wikipedia
