Tag Archives: adaptations

How do Bald Eagles stay warm in cold weather?

January 23, 2023: HD sports eye-cicles on a frosty morning in Decorah. An icy fog left everything coated with frost

Each species experiences the world differently and eagles have capacities that are far different from ours. How do Bald Eagles survive an Iowa winter without adaptive clothing and central heat? After a very warm week, temperatures plummeted on Saturday! When I jumped into my car to begin our Golden Eagle Survey, it was 25 degrees. By the time I got home late Saturday night, it was 5 degrees and the temperature was dropping fast! I checked our camera operators’ logs,

Eagle Eyes!

January 6, 2025: DNF's nictitating eyelid. This translucent third eyelid sweeps in from the side to moisten and protect her eye without obscuring her vision. More on eagle eyes here: https://www.raptorresource.org/2025/01/10/eagle-eyes-2/

Has anyone ever called you eagle-eyed? Relative to humans, bald eagles have larger, sharper eyes that see further, collect more details, and produce stereoscopic vision to greatly improve depth perception. A bald eagle’s visual acuity begins with its eye size and shape. Mr. North’s somewhat tubular eyes occupy over 50% of the volume of his skull, as compared with less than 5% in us spherically-eyed human types.  He can voluntarily adjust the curvature of his large cornea and lens (we’re

Oh poop shoot! What is bird poop and how do birds poop?

April 16, 2024: Mr. North, DN17, and DN18. It's hard to separate food and metabolic waste when they exit from the same place.

Oh poop shoot! After a long, wet morning snuggled under Mombrella and Poptent, DN17 and DN18 needed to let it fly! Wonderful moments like this inevitably lead to questions and comments like “What is bird poop?” and “Does bird poop stink?” and ‘Ewwww…where did I put those wet wipes?‘ So what is bird poop and how do birds poop? Defecation and Excretion If someone tells us their dog pooped, defecated, or excreted, we know that the dog dropped a solid.

Canada Geese: Precocial versus Altricial

April 14, 2024: The last gosling hatches at N1.

As watchers know, Canada geese are nesting in two abandoned bald eagle nests in Decorah, Iowa. N2B – currently a goose nest – is located about 700 feet east of N1, where geese started hatching yesterday. This blog discusses some of the differences between altricial eagles and precocial geese!  Altricial eaglets rely on parental care until they fledge. But goslings are precocial: capable of moving around, self-feeding, and leaving the nest shortly after hatch. What does that mean? Read on

What’s Up With the Geese? Canada Geese, Reproduction, and Conspecific Brood Parasitism

April 1, 2024: the resident geese struggle with the intruder.

On Saturday April 1, goose watchers at N2B saw a female goose fly into the nest. After a lot of biting, pushing, and tussling, she laid an egg despite MG and PG’s best attempts to repel her. One of the local eggs dropped out of the nest, although MG and PG ended up incorporating the intruder’s egg into their own clutch. At one point, it was thought that Canada geese were strictly monogamous. Close observation has yielded a more nuanced

Bald eagle tongues and beaks!

March 25, 2024: DN17 and 18 eat.

We know that bird beaks are specialized for feeding and daily tasks. Birds of prey have strong, curved beaks with sharp edges to help them tear meat. Falcons specialize even further, adding a tomial tooth to help them kill prey. Dabbling ducks have tiny, comb-like structures on their beaks to strain small animals, insects, and plants from water and mud, while piscivorous ducks have saw-like structures to help them hold on to struggling fish. But what about bird tongues or,

Birds and Daylight Length

December 20, 2023: DNF and Mr. North

Many temperate and arctic animals and birds react to daylight length. Photoperiodism entrains their physiology and behavior, which helps them respond to adapt to seasonal changes in the environment. Although bird species vary in their responses, daylight length drives the annual cycle of temperate and arctic birds overall. How do birds detect changes in day length? Like many other creatures, they use photoreceptors – specialized cells that detect light and initiate a physical response. The photoreceptors in birds are not

Bald eagle tongues and beaks!

March 25, 2024: DN17 and 18 eat.

We know that bird beaks are specialized for feeding and daily tasks. Birds of prey have strong, curved beaks with sharp edges to help them tear meat. Falcons specialize even further, adding a tomial tooth to help them kill prey. Dabbling ducks have tiny, comb-like structures on their beaks to strain small animals, insects, and plants from water and mud, while piscivorous ducks have saw-like structures to help them hold on to struggling fish. But what about bird tongues or,

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