TX Bat Swarms Can Be Tracked By Radar; Spring Arrival Now 2 Weeks Earlier Than 20 Years Ago

[hatrack]

When millions of migrating bats fly toward their breeding cave near San Antonio, Texas, each spring, the shadowy, swirling swarm is so dense, it shows up on weather radar. Scientists reviewed years of that radar data and found that the flying mammals are arriving about two weeks earlier than they did just two decades ago.

The scientists suspect the changes in the bats' timing and seasonal cycles are linked with the way global warming is altering the food chain and weather patterns.

Spring is warming faster than other seasons in many parts of the world, including Texas. An earlier bat migration fits with many pieces of the climate change puzzle, including earlier migrations of some bird species and earlier blossoming of many plants, said Phillip Stepanian, a meteorologist with Rothamsted Research who co-authored a new study in the scientific journal Global Change Biology on bat migration using the radar data.

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Successive images from the San Antonio/Austin weather surveillance radar show a swarm of bats leaving Bracken Cave. The cave entrance is marked by the red box. Credit: Stepanian and Wainwright, 2018

"We're able to see there is this advancing pattern. Spring is happening earlier, winter is ending sooner," Stepanian said. "In the spring, the bugs advance up from Mexico, hitting Texas, hitting Kansas and, suddenly, the bats have something to eat." That may also explain why the number of Brazilian free-tailed bats now staying through the winter in Texas' Bracken Cave has swelled in recent years. Surveys in the 1950s found no bats spending the entire winter there, but in 2017, as much as 3.5 percent of the entire population—100,000 bats—remained during the winter months, Stepanian said.

EDIT

https://insideclimatenews.org/news/14022018/bat-migration-climate-change-texas-agriculture-weather-radar-global-warming-animal-impact

[DUgosh]

1. I live west of San Antonio

I’ve been actively feeding hummingbirds in the Texas hill country for 30+ years. The travelers going north start stopping by 2 months earlier, the resident scouts about six weeks, the resident males 5 weeks, and the resident females four weeks earlier than when I started. I’ve had as many as forty females raising babies in a drought year. Last year with plentiful rain and flowers I had about 15.