Finding out why birds are out of range

A teen scientist studied how to predict miniature bird migrations to unexpected places

evening grosbeak

This evening grosbeak is sometimes found outside its normal winter range, having taken a journey called an irruption.  

Cephas/Wikimedia Commons

WASHINGTON, D.C. — Snowy owls are majestic predators, associated with ice and snow (and of course, Harry Potter). People in the United States normally do not see them in the winter, however. Snowy owls usually spend their winters farther north. But in 2012, many of these birds wintered at U.S. sites from Boston to Oregon. They weren’t alone. Smaller birds such as red crossbills and evening grosbeaks were wintering in the United States, well south of their normal seasonal ranges.

This feathered invasion was an irruption — the arrival birds from one or more species into a region where they aren’t supposed to be at that time of year. And Max Pine, 17, was watching. As he began to wonder why these birds might be making these abnormal appearances in some years, but not others. Could climate play a role? He decided to probe climate data and bird counts to find out.

Max is now a senior at Pelham Memorial High School in Pelham, N.Y. His project on climate and bird irruptions earned him a trip to the Intel Science Talent Search. Every year Society for Science & the Public and Intel bring 40 high school seniors here for the event. They present their research to the public and compete for cash awards of up to $150,000.

Irruptions are not like migrations. Many bird species migrate regularly, moving from one habitat to another in the spring and fall. Birds may migrate to nesting grounds to raise their young. Later, they may travel to better feeding grounds when the young are able to fly. But irruptions are irregular. They occur during the winter, but not every year. Indeed, many species that irrupt do not migrate with the seasons at all. Instead, every few years a group of birds — sometimes many species together — end up far south of their normal wintering grounds.

Irruptions may result when birds can’t find enough food in their normal haunts. Irruptions also may occur when a bird population has exploded in number. With many more mouths to feed, these birds now may need to fly elsewhere for food.

Max thought that climate might also help scientists predict when birds are going to irrupt. To find out, he did not go bird watching. Instead, he turned to his computer.

He accessed data from the yearly Christmas Bird Count. It collects information from across North America on what birds have been seen and where. The teen focused on nine different species including the red-breasted nuthatch, the evening grosbeak, the common redpoll, the bohemian waxwing and long-tailed titmouse. There had been more than 10 million sightings of these birds over the previous 60 winters. He then looked for information on weather in North America for the same period, using a database available from the National Oceanic and Atmospheric Administration. “It was all free,” Max notes. “You don’t even have to ask for the climate information.”

And using statistics, the teen linked winter bird irruptions to periodic shifts in the normal climate. One example: the arrival of El Niño. These are occasional, prolonged periods when water around the equator in the eastern and central Pacific Ocean warms more than usual. This regional change is linked to unusual weather all over the world. In North America, it can cause ice storms and droughts.

The links that Max made between climate patterns and bird irruptions were not perfect. Not all the bird species irrupt at the same time, and not all irrupt in response to the same patterns. Some may be more likely to irrupt if an El Niño had developed six months earlier. Others may be more likely to irrupt in response to another climate pattern, a La Niña — when water around the equator in the eastern and central Pacific Ocean is cooler than usual.

Max hopes that his findings might help scientists better predict irruptions. If scientists can predict when species are going to irrupt, they might also be able to predict how long-term climate change might affect bird behavior.

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Power Words

(for more about Power Words, click here)

climate   The weather conditions prevailing in an area in general or over a long period.

climate change  Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.

database  An organized collection of information. 

El Niño  Extended periods when the surface water around the equator in the eastern and central Pacific warms. Scientists declare the arrival of an El Niño when that water warms by at least 0.4° Celsius (0.72° Fahrenheit) above average for five or more months in a row. El Niños can bring heavy rainfall and flooding to the West Coast of South America. Meanwhile, Australia and Southeast Asia may face a drought and high risk of wildfires. In North America, scientists have linked the arrival of El Niños to unusual weather events — including ice storms, droughts and mudslides.

grosbeaks    Seed-eating birds with large beaks. The word “gros” is French for large, so grosbeak means “big beak.”

habitat  The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.

Intel Science Talent Search    An annual competition run by Society for Science & the Public and sponsored by Intel Corp. Begun in 1950, this event brings 40 research-oriented high school seniors to Washington, D.C. to showcase their research to the public and to compete for awards.

irruption   (v: to irrupt)  A sudden increase in a population. This may mean a larger number of animals in the normal range, or a population observed far away from where they are normally seen.

La Niña  Extended periods when the surface water around the equator in the eastern Pacific cools for long stretches of time. Scientists will announce the arrival of a La Niña (lah NEEN yah) when the average temperature there drops by at least 0.4° C (0.72° degree F). Impacts on global weather during a La Niña tend to be the reverse of those triggered by an El Niño: Now, Central and South America may face severe droughts while Australia floods.

migration  (v: to migrate) Movement from one region or habitat to another, especially regularly and according to the seasons.

National Oceanographic and Atmospheric Administration, or NOAA   A science agency of the U.S. Department of Commerce. Initially established in 1807 under another name (The Survey of the Coast), this agency focuses on understanding and preserving ocean resources, including fisheries, protecting marine mammals (from seals to whales), studying the seafloor and probing the upper atmosphere.

nuthatch  A genus of birds that live in the Northern Hemisphere and in Southern Asia. They have short tails, large heads and pointed beaks which they use to eat insects, nuts and seeds.

predator  (adjective: predatory) A creature that preys on other animals for most or all of its food.

redpoll  A group of birds in the finch family with characteristic red marking on their heads. They eat seeds and live in northern woodlands.

Society for Science and the Public (or SSP)  A nonprofit organizationcreated in 1921 andbased in Washington, D.C.Since its founding, SSP has been not only promoting public engagement in scientific research but also the public understanding of science. It created and continues to run three renowned science competitions: The Intel Science Talent Search (begun in 1942), the Intel International Science and Engineering Fair (initially launched in 1950) and Broadcom MASTERS (created in 2010). SSP alsopublishes award-winning journalism: in Science News (launched in 1922) and Science News for Students (created in 2003). Those magazines also host a series of blogs (including Eureka! Lab).

statistics  The practice or science of collecting and analyzing numerical data in large quantities and interpreting their meaning. Much of this work involves reducing errors that might be attributable to random variation. A professional who works in this field is called a statistician.

titmouse  A group of birds related to chickadees. They eat seeds and insects.

waxwing  A genus of birds with red tips on their wings.  They live in northern forests and eat berries.

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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