Biologist seeks to learn more about reddish egrets

Biologist Samantha Collins, for several seconds, intently studied the weight on her Pesola spring scale. Hanging from the instrument, nestled in a soft mesh cotton sack, was a reddish egret chick just weeks old. When the scale settled on 590 grams, Collins smiled and gently spoke to the bird that resembled something right out of a Jurassic Park movie, saying, “You’re a real fatty, aren’t you!”
Getting the chick’s weight was just one of several measurements the biologist meticulously obtains while gathering data on this particular species. Other measurements include the culmen (upper beak or bill), tarsus (leg bone) and wing length, all of which are critical in understanding the health and growth of reddish egret young.
A member of the ardeidae family of birds that include bitterns, egrets and herons, the reddish egret is listed as a Species of Greatest Conservation Need in the Louisiana Department of Wildlife and Fisheries’ Wildlife Action Plan. In fact, the species is ranked as an S1. In the plan’s explanation of rankings, S1 is defined as, “Critically imperiled in Louisiana because of extreme rarity (5 or fewer known extant populations) or because of some factor(s) making it especially vulnerable to extirpation.”
Collins, who works for the Louisiana Department of Wildlife and Fisheries out of the Rockefeller Wildlife Refuge office in Grand Chenier, since 2015, has led the department’s efforts to learn more about this rarest of heron species.
Collins said, “From some of the surveys we’ve done, it appears that reddish egrets are in very low numbers throughout the state. And, we really don’t know much about them. We don’t know where they’re selecting nesting habitat or on what islands.
“One big question we have is what foraging habitat do they use? So, we did a little bit of a pilot study in 2015,” Collins added. “We had Dr. Clay Green, a professor at Texas State University, come out here to southwest Louisiana to talk to us about what they’ve been doing in Texas. We had him show us some trapping techniques, show us how to bleed birds for genetic analysis and learn how to attach transmitters to them.”
Collins’s team utilizes 17g Solar Argos/GPS PTT Transmitters. Weighing just 17 grams, the solar-powered platform transmitter terminals have been invaluable in collecting important data that researchers need to better understand reddish egrets. Further, by altering a self-tripping trap design of University of Florida Re-search Professor Peter C Frederick that he used to capture colonial nesting birds, Collins has been able to successfully place transmitters on the adult birds she is studying.
As a rule, only healthy birds receive transmitters and only when the transmitter is less than 3 percent of its bodyweight.
Geographically, Collins uses Point Au Fer Island to basically divide the state into two study regions. Currently, she has 11 transmitters deployed in the southeast on adult reddish egrets and 12 transmitters in the southwestern part.
Population size and survival rates are extremely important to biologists. Therefore, learning what a certain species’ limiting factors are is crucial.
Now in her third year studying reddish egrets, Collins says the department’s efforts have garnered important data that has helped to answer some questions but also raised others.
Most of the data Collins has collected has been obtained by studying reddish egrets on Rabbit Island, located in the southwest corner of Lake Calcasieu. One of the things the department has learned about reddish egrets nesting on this island is they don’t have to go very far to forage compared to birds nesting on the eastern side of the state.
“Reddish egrets are looking for something in particular,” Collins said. “It’s one of the things we’re starting to see on Rabbit Island. What we’ve learned from the data so far is all of the birds that have transmitters don’t go very far to forage. The majority of birds on the west side of the state are sticking around. There’s a lot of good foraging habitat around Sabine National Wildlife Refuge and Apache Louisiana Minerals land, and these areas have nice clear shallow water.”
Though two of the Rabbit Island birds Collins placed transmitters on made trans-global migrations, going as far as Guatemala and Nicaragua, reddish egrets are considered semi-migratory, the biologist said. She pointed out, it’s not uncommon for them to make movements down the coast to Mexico.
By contrast, the eastern birds Collins has trapped and placed transmitters on, on Raccoon, Brandy and Queen Bess islands make very large movements between nesting and foraging areas.
Collins, who is heavily involved in the REEG Working Group that established the Conservation Action Plan for the species and is currently the leader for the research and monitoring committee, said, “They have certain areas they are looking for, especially where foraging is concerned. Over by Grand Isle, nesting islands are located within a bigger bay system not ideal for foraging, which could be one of their limiting factors there.”
During the time I accompanied Collins, one thing she did, without hesitation, was collect the vomit from the chicks she handled during banding. The regurgitation is somewhat common place during the handling process, according to the biologist, and essentially is significant additional data.
“While we were banding the chicks, we saw a lot of them regurgitating, so we said, ‘let’s collect that regurgitation and compare what they’re actually eating to what we collect from the foraging habitat sampling points.’ Once we started analyzing samples, we noticed a good number of the samples had these little worms in them,” Collins said.
The worms turned out to be parasites using the fish as secondary hosts. When the birds consumed the fish provided by their parents, they became the primary host.
Taking measurements and recording what the chicks eat and notating the condition of their health could provide answers to yet another potential limiting factor.
Collins says she gets her greatest satisfaction from the amount of information she’s been able to collect so far from the important study. Considering the department didn’t know much about reddish egrets in the state of Louisiana, it’s significant. But, there’s still much more to learn.
EDITOR’S NOTE: John K. Flores is The Daily Review’s Outdoor Writer.