The long, drawn-out Tadarida migration Fall 2017.  Play videos below this screenshot to see bats moving south from the Texas Hill Country over a three and a half week period from 24 Oct 2017 to 18 Nov 2017.

The first round of Hill Country migration appears to have been triggered by a cold front on 24 Oct 2017(UTC) and started on 26 Oct 2017 (UTC).
At first we wondered if this was normal foraging, taking advantage of the NW wind at only 5 mph.
But after monitoring over the next few weeks, we think many bats did indeed start leaving on 26 Oct 2017 (UTC).
Much colder weather seemed to stop southward movement from 28 Oct 2017 to 31 Oct 2017 (too cold to fly?)
Weather warmed quite a bit after that, showing lots of bats in the east. Roosts in the western Hill Country (Frio, Devil’s Sinkhole, and Fern) had smaller emergences over few days, but seemed to bounce back periodically (newly arriving migrants?).
Huber, Old Tunnel, and Bracken stayed large for a few weeks, either from retained summer residents or from newly arriving northern migrants.
The Hill Country (Huber Old Tunnel and Devil’s Sinkhole) mostly had cleared out by 10 Nov 20217.
Did Bracken bats move  to Frio 12Nov2017 UTC as start of their migration? Storm may have suppressed Bracken numbers; we’ll see.
Many colonies seem to split during the early part of migration, with some heading in a migratory direction, others in a foraging direction. More so than during the summer.
This year’s migration seems to be playing out over a 3-1/2 -week period.

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First wave of migration below


The next night, 26Oct2017, 1/5 as many bats at Devil’s Sinkhole, 1/2 as many at Huber and Old Tunnel,
but surges occurred periodically in most roosts over the next 3 weeks.
Radar Tadarida migration Fall 2017

Radar Tadarida migration Fall 2017

Radar Tadarida migration Fall 2017

Here’s Bracken data:

Radar Tadarida migration Fall 2017


Here’s more migration activity. Again, half (or more) of Huber bats, and what looks like all remaining Devil’s Sinkhole bats head SSW in definite migration pattern.  Very few from Old Tunnel, but what few emerged headed in a migratory direction.

And here’s the same night, 28OCT2017 UTC showing remaining Devil’s Sinkhole bats heading south for the winter.

As temps at emergence warm a little, more bats emerge. More than expected at Huber. Are these the remaining summer residents or newly arrived migrants from north?


Next warm night shows activity at Huber, Old Tunnel, McNeil, Congress, and Bracken, but Devil’s Sinkhole had very few bats fly.

After no flights recently (see chart below), the last ~200k of the Frio Cave bats head south to migrate through Eagle Pass.
The Frio Cave flight starts just north of Uvalde and heads southwest.

Here’s the times, direction, and reflectivity  for Frio from the first week or so:
Frio Cave fall 2017 migration, Mexican free-tailed bats

First warm night brings out more bats than previous chilly nights> Still another 200k from Frio that could have been hunkered down.

Migration on hold with recurrence of warm weather

Still on hold with possible exception of half Old Tunnel bats

Cold weather Oct 28-30 UTC
Warm weather Nov 3-5 UTC

Below, a cold front pushes through just before emergence at Bracken.
No bats appear to have emerged early to ride it south.

Here’s the night’s emergence soon after frontal passage.

No migratory movement noted even after storms passed a few hours after normal flight time

Second night of cold weather triggers Frio bats to resume migrating. Seems like 450k headed southward. Will they return?
Some Bracken bats also appear to be leaving. Stuart makes no obvious move. Nothing from Devil’s Sinkhole, Old Tunnel, or Huber, or anywhere else north of Wimberley.

Again Frio bats headed SW in migratory direction, likewise Stuart, but far fewer. Still lots of bats at Bracken. Nothing from Devil’s Sinkhole or Huber.
Tiny bunch at Old Tunnel.

Frio bats appear to head SW past (hopefully around or above) the Anacacho Wind Farm

Most of the Hill Country seems done. Nothing except at Fern and a few at Old Tunnel. Still a million or so at Bracken, but none at McNeil or Huber. Congress, surprisingly, still has ~90k.

Frio much larger than expected and Bracken diminished; possibly from storm but also possible some moved to Frio as part of migration.

Still lots of bats at Bracken and Congress. Half of Frio again heading SW in migratory direction.

Nothing from Congress on this warm evening. Did they leave last night? Radar does not show them leaving.
McNeil and Huber have had no emergences since 08 Nov 2017 UTC.
Devil’s Sinkhole appeared to be done at that same time but had a surge from 13 Nov 2017 to 15 Nov 2017, now next to nothing.

Still lots of bats at Bracken Frio and Fern.

The bats seem to be moving in stages with parts of the colonies moving in separate increments to more SW roosts.

Big surprise from Devil’s Sinkhole!

Surge from Fern, fewer at Foster St and Devil’s Sinkhole

Way fewer at Devil’s Sinkhole, surge at D’Hanis – did they move there?

Surely this cold front pushed the last of the Mexican free-tailed bats southward on their annual migration.
This video shows Fern Cave, two waves of bats from Devil’s Sinkhole, Frio, and Huber all showing massive numbers of bats moving in a migratory direction.

Here’s a black-background view of the same night.

Sure enough Bracken is a day behind, as usual. The majority of all other colonies seem to have left.
We’ll see on the next warm night, if there is one.

Lots of Central Texas bat activity on a chilly evening. Devil’s Sinkhole, Old Tunnel, and Huber really show up strongly because of their more isolated locations.  Still a strong flight from Congress, so our newly released bats have plenty of company.

This beautiful cave myotis (Myotis velifer) was hanging motionless in the same location for four days in the corner of Cait’s balcony. She was worried about him and was kind enough to contain him and have us check him out.  He turned out to be just fine! We fed and hydrated him for a few days and released him tonight. Thanks for caring Cait!

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These two girls were rescued from separate Houston apartment complexes back in June. They’ve been with us all summer and have just now recovered their strength.  The one on the left was not flying well just two weeks ago, but last week started sustaining flight and had the red “no-go” tag removed (actually red lip gloss on the ear). They’ll be so happy to be in the soft-release box; they can stay there until they find a great new home!

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Austin bat presentations education talks programs outreach

Latest research shows that 3 out of 4 Mexican free-tailed bats found in Saver’s Thrift Store prefer the Halloween department over other parts of the store.  Even though bats have nothing to do with Halloween 😉 , they nonetheless provided holiday ambience as they hung decoratively up with the fake cobwebs up in the ceiling! The other was recovered from over the cash register area, so perhaps the last one was making sure they got paid for their advertising efforts!

They all were fine, just wondering why Savers keeps inviting them into the store and then freaking out about it. Humans!

Here are three of the four a few days later, ready to be released under Congress Avenue Bridge, as soon as F1 takes down the fences for their party at the bat-viewing area.
Austin bat presentations, talks, outreach, programs, education, Mexican free-tailed bat, Congress Avenue Bridge bats

While they were resting up for their release, an immature Texas rat snake curled up under the roof tarp to stay dry and bask.  He was within a few inches of one of the boys and would have had him for lunch but for the netting in between them. Watch out you valiant little bats!

Here’s the rat snake getting relocated a few miles down the creek.

Here they are finally getting released at Congress Avenue Bridge after their circuitous adventure!
Austin bat presentations, education, outreach, talks, programs, rescue, rehabilitation
Austin bat presentations, outreach, programs, education, talks

Great work Di! The first two talks were to veterinarians at the Convention Center, the last one for the Rotary Club on their riverboat cruise.  The boat cruise was really great! The city looked beautiful at night and the bats were translucent in the bridge lights!

Austin bat presentations. talks, programs, education, outreach

Austin bat presentations, talks, education, programs, outreach

Austin bat presentations, talks, outreach, programs, education

Austin bat presentation, talks, outreach, education, programs

A recent episode of Rick Steves Europe titled “Greece’s Peloponnese” included Epidavros, the Greek healing center where doctor-priests performed the work of Esclepios, the Greek god of medicine. This center served Greeks from ~400 BC to 426 AD.

When demonstrating the acoustics of the 12,000 seat amphitheater that entertained those who traveled there for healing, Steves gave a speech meant to sound as if delivered by an ancient Greek: “Friends, Greeks, wayfarers, in these times of discord, fear is rampant in our society.  I contend that the flip-side of fear is understanding, and those who travel reap great understanding by meeting people who hold OTHER truths to be self-evident and God-given.”

We love this about Rick Steves and we wish that we could travel more to experience the truths of other cultures.  We hope that one day we can do so, but in the meantime, we get to have travelers come to us as we staff the information table at the Congress Avenue Bridge Bat Viewing Area.  Thanks so much to all the intrepid travelers who took the time to write in our Bat Journal!

In the future we’ll make a point of asking more about THEIR lives. Much as we love to have them log their impressions of the Austin bats, we want them to share THEIR truths and gain some insight into the way THEY see the world!

Congress Avenue Bridge, Congress Bridge bats, Austin bat education, outreach, programs, presentations, talks


Our former neo-nate D-Day had his big night last night!  He and all his classmates joined the Congress bat colony, in plenty of time to integrate prior to their migration south in a few weeks to come. So thrilling to watch them go!

D-Day was found on June 6th as a newborn pup clinging to the top of the bridge with just his feet and tail sticking up under the railing.
Dianne rescued him and hand-raised him and his free-tailed classmates from little specks, so tonight was emotional, as the end of their captive upbringing and the beginning of their new life as part of the wild Congress Avenue Bridge colony! Go with the bat gods, with the wind, with your guts, little pups!


Danielle O’Neil’s great photo of D-Day at 3 weeks:

Congress Ave. Bridge Bats, bat rehabilitation, bat education, bat presentations, bat programs, bat educational outreach, Congress Avenue Bridge, Congress Ave Bridge Bats

austin bat presentations talks outreach education programs presentations Congress Avenue Bridge bats

Just to train them correctly, we waited until all the tourists left before releasing them from the top of the grassy slope of the bat viewing area ;). (It seems the Congress colony waited to emerge until the crowd of tuna boats, kayaks, LED lights, and red lights went away, before they emerged.) So our pups will learn from the best!  That means, of course, that our pup also did not cooperate with the paparazzi, so no videos or photos of the release! Good bats! This photo from the flight cage earlier in the season.

People from Poland, France, and Alaska all came to see the emergence last night!  We love having our information table at the bridge to help inform the tourists about the bats.


Love you little bat!  Go have a happy happy life!

Here’s a last look at you pre-release

You look so good up there! Look at all those quick darting moves! Are you showing us how happy you are to be wild and free?

Here’s our boy pre-release. We’ll miss his antics and amazing leaf dancing!

And here’s his final wave goodbye!  He is a fine young bat and we have every confidence he will live a long and happy life!