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Tag Archives: adaptations

Egg Colors and Shapes

March 20, 2023 RaptorResource

The Chicago Peregrine Program inspired me to write a quick blog on the colors and shapes of eggs. Bald eagles have white eggs, peregrine falcons have eggs that range from light cream through brick red, and red-tailed hawks have pale eggs that are lightly splotched with brown. How and why do the birds we watch lay differently-colored and shaped eggs? Egg Colors Where do egg colors come from? Once a bird’s egg enters its shell gland or uterus, it is

How do eagles stay warm in cold weather?

January 27, 2023 RaptorResource

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? A cold January morning coated our eagles in frost and left watchers wondering how Bald Eagles survive an Iowa winter. In general, wintering animals – including humans – need to retain body heat, stay dry, and take in enough calories to support winter’s increased energy demands. We humans put on

Can birds detect severe weather? Storms, cold, and Bald Eagles in winter!

December 21, 2022 RaptorResource

Can birds detect severe weather? I’m watching the birds at my feeder as a major snowstorm rolls in. American Golden Finches, Dark-Eyed Juncos, Black-Capped Chickadees, and White-Breasted Nuthatches are decimating my seed feeder, while our resident Downy, Hairy, Red-Bellied, and Pileated Woodpeckers clean out my suet feeder. The feeder action started yesterday. Did our birds know a major storm was on the way? While birds can’t predict long-range weather patterns, they have at least two ways to detect and prepare

Eagle Vocalizations: HD, HM, and Morning Song

December 9, 2022 RaptorResource

HD, HM, Mr. North, and DNF vocalize by using an organ unique to birds: the syrinx, a small two-sided structure that allows birds to make complex sounds. Both sides of a bird’s syrinx are equally capable of producing sound and can be used alone or in concert to sing two different notes simultaneously and complete broad sweeps in pitch quickly. While singing ability and song role varies widely from species to species, a bird generally produces sound by modifying the

Canada Geese: Precocial versus Altricial

March 25, 2022 RaptorResource

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 to learn more! Canada Geese and Bald Eagles: Precocial versus Altricial From Stanford University: A precocial bird is “capable of moving around on its own soon after hatching.” The word comes from the same Latin root as “precocious.” Altricial means “incapable of moving around on its own soon after

Four Foraging Stories from the Flyway

October 29, 2021 RaptorResource

It’s late October and the birds we watch on the Mississippi Flyway are pouring south while local plant and animal populations dwindle in response to diminishing daylight length, colder temperatures, and reduced food availability. How do migrating birds find enough to eat in the diverse, rapidly changing habitats they travel through? Read these four foraging stories to learn more about how birds cope with the challenge of finding food on migration! River Dreaming Picture a Mississippi River lake: a lake

Eagle Eyes!

November 19, 2017 RaptorResource

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. Dad’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 restricted