White-tailed eagles (Haliaeetus albicilla) have several adaptations that allow them to stay warm in their cold environments. These adaptations include counter-current heat exchange in their legs, minimal soft tissue in their feet, and the ability to tuck one foot up against their body for quick warmth.

Counter-Current Heat Exchange in Legs

The counter-current heat exchange system in the legs of white-tailed eagles allows them to conserve heat by warming blood flowing back to the body with blood flowing to the feet. This system also cools the blood flowing to the feet, reducing heat loss. This is facilitated by the close proximity of blood vessels going to and from the feet, and the rapid circulation of blood in birds.

Minimal Soft Tissue in Feet

Image source: white tailed eagle by Andreas Weith

White-tailed eagles have minimal soft tissue in their feet, which reduces the amount of warm blood flow required to keep them warm. This adaptation helps the birds conserve energy and stay warm in their cold environments.

Tucking Feet for Quick Warmth

White-tailed eagles have the ability to tuck one foot up against their body for quick warmth. This allows them to use their own body heat to warm up their feet when needed. Birds may also alternate standing on one foot at a time, pulling one up into their warm downy feathers while the other stands in the cold, and then reversing them. When perching, birds can also lower their bodies down to cover their feet, keeping them warm with their feathers.

Physical Measurements

In terms of physical measurements, white-tailed eagles in the British Isles have a wing-span of around 2.5 meters (8 feet), varying between the smallest male to the largest female. Young white-tailed eagles are covered with thick, cream-coloured down feathers and are still kept warm by their parents at the age of about 3 weeks.

Basking in the Sun

When white-tailed eagles are not on land, they can be found out at sea feeding on fish. Upon returning to land to rest and warm up, they like to bask in the sun. This behavior is especially common in Scotland, where white-tailed eagles, seals, and otters are among the country’s amazing wildlife.

Conclusion

White-tailed eagles have evolved several adaptations to stay warm in their cold environments. These include counter-current heat exchange in their legs, minimal soft tissue in their feet, and the ability to tuck one foot up against their body for quick warmth. These adaptations, along with their physical characteristics and behaviors, allow white-tailed eagles to thrive in their cold habitats.

References:
– https://www.isle-of-mull.net/wildlife/eagles/white-tailed-eagles/fly-like-an-eagle/
– https://www.suecoletta.com/secret-life-of-eagles/
– https://www.allaboutbirds.org/news/why-dont-birds-get-cold-feet/
– https://wislawarszawska.pl/white-tailed-or-sea-eagle/?lang=en
– https://www.robertefuller.com/diary/white-tailed-eagles-seals-otters-scotlands-amazing-wildlife/