How hurricanes can trap and transport birds

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(WUTR/WFXV/WPNY) – Hurricanes are known for their power and destruction, but what about a bird trap? Well, a novel study conducted by Matthew Van Den Broeke, an associate professor of Earth and atmospheric sciences at the University of Nebraska–Lincoln, gives a glimpse into how this happens.

“Reports of birds being trapped in the center of hurricanes date back to at least the 19th century when crews observed the phenomenon from the bows of ships and saw their vessels become mobile ports for exhausted birds,” says Broeke. “We’ve known for a long time that this happens… but it’s really only since (the advent of) radar observations that we have gotten any sense of how many of these systems actually do transport birds and insects.”

The type of radar Broeke is referring to is dual-polarization radar. Radar, which stands for radio detection and ranging, normally sends out a beam of energy, called radio waves, which move outward, striking objects in the atmosphere. As the beam hits an object like a raindrop, its energy spreads out, but some of its energy bounces back to the radar. This gives meteorologists the ability to see raindrops in the atmosphere and tell how far away they are. 

Dual polarization radar differs from the standard radar because instead of sending out one beam that’s horizontal, it sends out a second beam that is vertical. This makes it easier to determine the size, shape, and variety of objects in the atmosphere. Van Den Broeke set out to analyze the dual-polarization data from 33 Atlantic hurricanes that struck either the U.S. coast or Puerto Rico between 2011 and 2020. He was looking specifically for bioscatter signatures which are electromagnetic waves that bounced back to a radar station from birds and in some cases, even insects.

In every one of the 33 cases, Van Den Broeke identified at least some bioscatter. His results also concluded that the greater the wind speed of a hurricane, the denser and sometimes larger the bioscatter signature was, indicating the presence of more birds within the eye.

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