When rain is predicted you might open a weather app to check when the storm will roll in, viewing radar imaging to pinpoint the moment you need an umbrella. Weather radar is, of course, used to track precipitation. But not everything in the sky is a meteorological phenomenon - a perhaps lesser-known use of radar is bird migration monitoring.
Depending on the severity of the weather, flying fowl can be distinguished from raindrops due to their movement and speed; real-world observations can help corroborate. Researchers from Colorado State University (CSU) used weather radar and datasets to assess the popularity of urban areas during migration season and published their findings in Nature Cities.
Dr. Mikko Jimenez, currently a researcher with Lincoln Park Zoo’s Urban Wildlife Institute and formerly a doctoral student at CSU, led the study, which showed a higher-than-expected dependency on cities. Nearly half of the zones considered stopover ‘hot spots,’ where birds refuel and rest, are in metropolitan regions with 50,000+ residents. This could be the case because reliable water sources tend to be found in urban areas but not necessarily elsewhere. In the west especially, green spaces may be few and far between.
This unequal distribution can lead to a ‘luxury effect,’ where resource inequality causes birds to prefer wealthier zip codes. At the continental level, a positive relationship does exist between income levels and stopover density, resulting in greater biodiversity in more affluent sections. However, when analyzed at a city level, that relationship does not always hold. Generally, birds seem to prefer metropolitan areas in the west, while favoring less populous locales in the east.
The CSU study highlights the importance of keeping Chicago and other cities safe and bird-friendly by turning off lights, using window-collision deterrents, and planting native plants. As we look forward to fall migration and beyond, these are essential actions to make the long, dangerous flights a bit easier on birds.
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