John K. Flores: Geolocator study focuses on birds' migration on the Gulf

It’s mid-June at Palmetto State Park, located just south of Abbeville. It’s also early in the day; the time of morning where campers are just starting to stir around for their first cup of coffee, oblivious to the singing of warblers in the trees outside of their RVs.
Louisiana Director of Bird Conservation Erik Johnson and I have already checked a half dozen or so nest boxes with hopes of catching a prothonotary warbler to attach a geolocator transmitter to. One of the boxes had a female sitting on a clutch of eggs. Sensing danger, she flushed from the box prematurely and avoided capture.
She didn’t fly far. In fact, just far enough where she felt safe and could feign injury to draw our attention away from her nest — something people have seen killdeer do in their driveways.
For over two decades avian geolocators have been instrumental in helping biologists track and key in on bird movements and migration patterns from the wintering grounds to the breeding grounds. What’s more, according to Johnson, Palmetto State Park played a role in some of the early geolocator studies.
Johnson, who resides in Sunset, said, “We’ve probably banded over 100 adult prothonotary warblers here. This was a site that we used in our first geolocator study, in like 2014, 2015, and 2016, and that was the study that showed that breeding birds from across the range winter in northern South America.”
Johnson pointed out that the original study included partners from Arkansas, Ohio, South Carolina, Virginia and Wisconsin. Of the 100 geolocators deployed, 33 from those multiple states were recovered. Moreover, 31 of them showed a wintering ground in northwestern Columbia.
After checking several more nest boxes, Johnson decides to double back and recheck the box that the female flushed from.
Johnson said, “They’re one of the great species to study. They’re incredibly accommodating with all the things we throw at them. Obviously, it just takes a minute or two to check the box, but often we’ll flush the female off when she’s incubating, and she’s back in a few minutes checking on her eggs, and settling back in. When we catch the female, she tends to go right back. We hardly have any abandonment issues.”
Over the years, many of the predator-guarded nest boxes on Palmetto State Park were built by 4-H volunteers from Acadiana High School under the direction of Brandon Broussard. Others were built by a Loreauville High School shop class. And, even some with a higher level of sophistication by retired UL-Lafayette Computer Science Professor Jim Ethridge, who incorporated a QR code, where a cell phone can be used that will take you to a website where nest monitoring data is being collected.
Johnson quietly slips through the woods to the skittish female’s nest box and places a makeshift hand net he specifically built for this purpose over the entrance hole. This time, she flushes into it.
While examining the prothonotary warbler to see if she is a good candidate for a geolocator, Johnson sounds like he’s running down a checklist as he narrates the process to me.
“She’s got good body weight,” he says, “very little wear on the feathers. Everything is fresh. She has lots of white on the tail. She’s got some nice pre-alternate lore limits — like real bright yellow over the lores over the eyes. Really nice. She’s on the upper spectrum. She’s just a good-looking bird.”
I tease Johnson, who was clearly delighted with the bird’s physical attributes saying, so, what you’re telling me is, “she’s a brick house,” taking a line from The Commodores 1977 hit. After all, the bird is to be fitted with a 0.5-gram geolocator that she’ll wear for at least a year.
Johnson, clearly amused by my analogy, tells me it would take 1,000 geolocators of this size to equal one pound. Putting it another way, it’s the equivalent of a 200-pound man carrying an extra 8 pounds.
The thing about geolocators is the bird must be recaptured on the breeding grounds where the unit was deployed to retrieve the information. Now, nearly a decade later, Johnson’s current geolocator project comes with a huge technical advancement.
Johnson said, “Geolocators have evolved. You can add a barometric pressure sensor to the geolocator, which weighs almost nothing. It records barometric pressure every 20 minutes while the tag is on and over the course of the year it’s logging that data, but you can match barometric pressure to different parts of the planet.
“There’s a global barometric pressure data base that is hourly for every 30-by-30-kilometer square on the planet,” Johnson continued. “So, pressure changes obviously depending on weather pattern — you get cold and warm fronts — and just daily fluctuations. Through a computer program you can basically match up what you’re seeing on the geolocator against signals that you see around the planet and home in on the probable location of the bird in any given minute.”
Essentially, the barometric feature provides biologists with more resolution than the original geolocators by providing more accuracy and confidence to the bird’s migration location and timing.
The barometric pressure feature also provides biologists with another critical piece of information.
Johnson said, “Now we can estimate flight height and that is the real impetus of this study. We need to know how high birds are flying when they’re migrating, especially over open water, such as the gulf, where there is an interest in deploying offshore wind energy.”
Johnson says the latest geolocators will allow researchers to know when birds are flying within potential collision zones. Overland, he points out, birds migrate at 3,000-5,000 feet. When there is inclement weather, they can drop out of the sky and hang out in the trees, where over water they must push through.
Stressing some of the tallest wind turbines can potentially reach nearly 1,000 feet, Johnson said, “we think what happens is that birds will come lower into the atmosphere during periods of bad weather and that’s when they’re going to be at most risk colliding with wind turbines — when they’re making those migrations over the Gulf.”
Johnson says one of the goals researchers hope to achieve is the ability to predict those weather patterns that bring birds lower into the atmosphere. “Let’s say a cold front is coming in and we know that lots of birds are going to be migrating over the gulf during that particular week — and we can say, ‘hey, there’s an 86 percent probability that there will be birds in the air space,’ maybe they can shut off turbines, or curtail them, or mitigate in some way. Right?”
At a time where climate change and an endless demand for energy are often at a crossroads with one another, Johnson makes note that conservation is where you are. He mentions over 95 percent of the U.S. has been converted for one human use or another and has been impacted by pesticides, invasive species, hydrology and other changes. His contention is, conservation isn’t an over there thing. It’s something we all can do.
John Flores is the Morgan City Review’s outdoor writer. He can be contacted at gowiththeflo@cox.net.