Birds on the move: Finches and owls take flight

Nothing in nature stays the same. Nature is always in flux, best described as fluid and adaptive. Once you embrace these simple truths, answering some of nature’s questions becomes easier.

Every few years, bird species such as common redpolls, pine siskins, evening grosbeaks, and others move out of their normal winter ranges in search of food. These birds are often referred to as “winter finches.” This mass movement of birds is known as an irruption.

The study of irruption behavior is challenging because it involves events that occur irregularly and are difficult to predict. Additionally, the birds travel great distances, making them harder to track.

In the past, the irruption of winter finches has been attributed to a lack of food in their home range. These birds feed on seeds from conifer trees. People often seek explanations for every behavior observed in nature, and the lack of food seemed like a reasonable explanation for winter finch irruptive behavior.

It is natural to assume that irruptive behavior in other bird species, such as owls, must also be triggered by a lack of food.

For example, there was once a belief that when lemmings overpopulated, they committed suicide by jumping off cliffs. This idea was popularized by a Disney production in 1958-59 titled “White Wilderness,” which claimed lemmings killed themselves by leaping into the ocean.

In 1983, a Canadian Broadcasting Corporation investigation found the scenes were staged, with the production team pushing and throwing lemmings off a cliff. While Disney didn’t start the myth, the film amplified it with false depictions.

Similarly, the decline in lemming populations was incorrectly linked to the irruptive behavior of their primary predator, the snowy owl. We assumed that snowy owl irruptions, like those of winter finches, were due to a lack of food—but this assumption was incorrect.

Today, we understand more about irruptive behavior, but much remains unknown, especially in snowy owls.

Research into snowy owl irruptions shows that these birds are often extremely healthy and well-fed when they move beyond their natural range. The current theory is that an abundance of food allows snowy owls to reproduce in greater numbers, which may trigger their irruptive movement. This is the exact opposite of what was previously assumed.

This winter, many northern states are experiencing an irruption of great gray owls and boreal owls.

Dozens of these birds are appearing in areas where they are not typically found. Their presence is drawing bird watchers and photographers from across the country, eager to catch a glimpse of these rarely seen species.

Studies on the irruptive behavior of great gray owls and boreal owls are limited. As is often the case when information is lacking, people tend to create ideas and explanations to fill in the blanks.

While most reports of great gray owls and boreal owls admitted to wildlife rehabilitation centers involve injuries, often from automobile collisions, these birds are generally in good physical condition and well-fed.

Despite these findings, the idea that birds irrupt out of their normal range due to a lack of food persists. Something doesn’t add up.

We often want to point to one specific reason to explain behaviors in nature.

In reality, it’s often a combination of factors that trigger visible behaviors, rather than a single cause like a food shortage. Over the past 20 years, we’ve learned that much of what we believed about bird behavior isn’t true. This serves as a reminder not to make bold, sweeping generalizations without personal knowledge or evidence.

What is true is that old myths can take generations to fade, and new scientific data is often ignored for decades. We seem slow to forget old ideas and reluctant to embrace new ones. Until next time …

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Editor’s note: Stan Tekiela’s NatureSmart column appears twice a month in the Eden Prairie Local News. Tekiela is an author, naturalist, and wildlife photographer who travels extensively across the United States to study and capture wildlife images.

You can follow his work on Instagram and Facebook. He can be contacted via his website at www.naturesmart.com.