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(1/6) Once upon a time, we used a 23-year dataset of radar observations to produce nightly surveys of a large bat colony in Texas. It was a fun project.
We found that spring migration from wintering grounds in Mexico was systematically advancing toward earlier arrivals in Texas. https://twitter.com/RadarAndStuff/status/963871306935660544
We found that spring migration from wintering grounds in Mexico was systematically advancing toward earlier arrivals in Texas. https://twitter.com/RadarAndStuff/status/963871306935660544
(2/6) At the time, we weren’t able to tie these shifts in bat migration phenology directly to a clear cause, but it seemed possible that these changes were a response to some climate signal. https://www.scientificamerican.com/article/bats-are-migrating-earlier-and-it-could-wreak-havoc-on-farming/
3/6 These bats require flying insects for food. We speculated that warming spring temps = more bugs earlier in the season (by faster degree-day development or exceeding min flight temp thresholds earlier), providing the food to sustain earlier bat arrival. https://www.newyorker.com/news/dispatch/the-changing-climate-inside-the-worlds-largest-bat-colony
4/6 Luckily this question attracted the interest of @Birgen_Haest, who applied his keen analytical expertise to the dataset. Searching over a set of weather variables—across locations, altitudes, and seasons—he found a match to the shifting bat arrivals. https://onlinelibrary.wiley.com/doi/10.1111/gcb.15433
5/6 The culprit is indeed a changing climate, but in an unexpected way. More frequent southerly springtime winds (925-850mb) over northern Mexico are providing more (and earlier) favorable opportunities of tailwind support for bats to migrate north to TX. https://www.independent.co.uk/environment/climate-change/bat-migration-climate-change-us-b1722435.html
(6/6) In hindsight this explanation is very satisfying, but I never would have predicted it. @Birgen_Haest's work really highlights the complexities of understanding changing global weather patterns on migratory animals. #aeroecology #bats 
Probably just cap off this thread with a live look at the Bracken Cave bat colony taking flight... because #bats
