Northern Cardinals are known for their iconic red feathers, yet that scarlet hue is actually derived from yellow pigments in their food. Most cardinals’ bodies transform those yellow pigments into their signature shade of red, but some lack this ability — resulting in a bright yellow bird. House Finches, Red-bellied Woodpeckers, and other notably red species can also develop an unexpectedly golden complexion. So keep an eye out for all the shades of variation in well-known birds.

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Red-tailed Hawks typically have a nesting territory of about a half-mile to a full square mile, depending on how much food there is. Bald Eagles’ nesting territories range from 2½ square miles to as much as 15 square miles, for the same reason. But the Gyrfalcons in Finland and Scandinavia really need their space!

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Everybody’s heard of a gaggle of geese and a covey of quail. But what’s a group of penguins called? And a “conspiracy” of ravens? Maybe the way we label birds says more about us than it does about them.

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Collecting data on wild birds is crucial for their conservation. But it requires huge amounts of effort. One way to help streamline the process is with gizmos called autonomous recording units, or ARUs. For days or months, these recording devices eavesdrop on the environment around them, including the songs and calls of the local birds. Identifying the songs picked up on recordings can be almost as time-consuming as in-person field work, but new AI tools are quickly making it easier to analyze the audio.

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Sometimes all you need to identify a bird is a single feather. Because collecting bird feathers is prohibited in the U.S. to protect birds from poachers, start by taking a photo with a common object for scale. Then you can use online resources like the iNaturalist app or Featherbase website to help you solve the mystery. Keep your prime suspect in mind when you’re back where you found the feather and you might get to see the bird itself — feathers and all.

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The challenge of learning which gull is which brings to mind a crossword puzzle. Take in all the clues, and come up with the right answer. For identifying gulls, we recommend a good bird book, binoculars, perhaps a thermos of hot coffee, and maybe a chair. So which gull is this? Large gull, dark back, pink legs, seen in the West. This one is a Western Gull!

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Around this time of year, Common Mergansers cross the U.S.-Canadian border on their way to wintering grounds in the Lower 48. But how do they know when to go? Ducks are well insulated against frigid winter temperatures, but mergansers can find their fishy prey only by diving below the surface of open water. So they’re doing just fine, resting and feeding in southern Canada, until a thin veneer of ice forms on their lake, signaling the time has arrived to head south!

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Every year, hundreds of bird species migrate between North and South America. Some species likely evolved from ancestors that moved north in search of new breeding habitats: the “southern home” hypothesis. But others may have extended their winter ranges south: the “northern home” hypothesis. Many birds have likely gained and lost the ability to migrate multiple times over the course of evolution. And it’s still happening today.

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Window collisions kill nearly one billion birds every year in the U.S., with many fatalities occurring during spring and fall migration. Judy Pollock, president of the Chicago Bird Alliance, says this problem has a solution: using bird-safe glass or applying a tight grid of decals to existing windows to make them easier for birds to see.

Though many building owners are reluctant to make these much needed changes, Judy and her collaborators are advocating for a city-wide ordinance that would require new construction and major renovations in Chicago to use bird-safe glass. Learn more about Bird-Friendly Chicago in our latest episode of Bring Birds Back.

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In the tidal marshes of the East Coast, the Saltmarsh Sparrow has a breeding strategy described by scientists as featuring an “obligate, promiscuous, and bond-free relationship between males and females.” That means both sexes copulate with multiple individuals, without a lasting relationship. The female is singularly responsible for nesting and hatching and drives off males that approach while she is raising her young.

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