Connecticut Audubon Society hosted its second of five Young, Gifted, And Wild About Birds online presentations on Thursday, February 10.

Sam Apgar led the “High Tide for Salt Marsh Birds” program to shine light on how salt marsh birds are experiencing nest flooding due to high tides.

According to Connecticut Audubon Communications Director Tom Andersen, “Sam is a PhD candidate at the University of Connecticut and is working on the final stages of her dissertation. She is studying how rising sea levels are affecting Saltmarsh Sparrow, Clapper Rail, Willet, and Seaside Sparrow, all of which nest in Connecticut’s tidal marshes.”

During the presentation, Apgar noted that her presentation is based off her dissertation work and findings thus far.

She shared, “No research is done in a vacuum. There are a lot of different groups that have supported my work either financially or in terms of allowing me site access to do my work and collect my data. In terms of field crews, undergraduate volunteers and independent study students have helped me collect the data and analyze the data.”

For some background, she explained that tidal marshes are ecosystems found on the interface of oceans or bays and further upland environments. They are mostly dominated by grasses.

“Another really important thing about tidal marshes is that they are tidal,” Apgar said. “You have two high tides and two low tides every day, and you have higher high tides around the new or full moons. So, the degree to which the marsh floods is dictated by a lot of factors, but the moon really dictates it quite a lot.”

With that in mind, birds that nest on the ground in these marshes will inevitably face some sort of nest flooding.

She shared images of a dry Clapper Rail nest during the day and the same nest submerged in water about six hours later due to the high tide.

“Even though it seems pretty intense, these birds have been dealing with these conditions for a long time. These species have been living and reproducing in marshes for thousands of years, so they have some tools to deal with some amount of nest flooding,” Apgar said.

She highlighted the Saltmarsh Sparrow, which nests in marshes, and indicated that there is research showing the species of bird is declining rapidly due to sea level rise and other factors.

“The Saltmarsh Sparrow is declining specifically at a rate of 9% per year, which is the greatest decline out of all the species that were studied,” Apgar reported.

Why The Decline?

To study the decline, 23 sites across the coast were set up to monitor nests.

“Largely it was found that, unfortunately, Saltmarsh Sparrows are not able to fledge enough chicks, because of nest flooding — either eggs flooding out during the egg stage or chicks drowning in the chick stage and not able to get out of the nest successfully … extinction is probable for this species,” Apgar said.

However, she reported that other birds that nest in salt marshes have different data trends.

Seaside Sparrow and Willets are exhibiting stable population trends, Nelson Sparrows are declining at a rate of 4.2% a year, and Clapper Rail are declining at a rate of 4.6% a year.

Apgar studied why the Saltmarsh Sparrow is seeing the most decline compared to other similar salt marsh nesting species even though they are all dealing with the same stressors.

She used infrared video cameras at two sites in coastal Connecticut — Hammonasset Beach State Park and East River — to study how the birds behaviorally responded to nest flooding events at night and if it impacted their fates during high tide.

Apgar was able to collect more than 400 hours of video footage, and she presented a clip of a Saltmarsh Sparrow nest during the presentation.

She found that the adult birds spent less time incubating eggs when the nest was wet and less time after chicks are born, whether the nest is wet or not.

For Willets, she showed a sped-up video of three eggs in a nest that began to float as the water flooded the nest. Two eggs eventually started to drift out of the nest cup area.

“This video is kind of emblematic for a lot of the species, but specifically for Willets. They are really not spending much time at all at nests when they’re flooding,” Apgar said. “Clapper Rails on the other hand do spend a little bit more time than the other species at the nest when they are flooding.”

She then showed a video of how an adult Clapper Rail used its bill to move around blades of grass while the nest was flooding to stop eggs from flooding out. She noted that in some cases other studies have shown Clapper Rails go out and retrieve the eggs that have been flooded out of the nest.

Apgar also discussed nestlings and showed a video of Saltmarsh Sparrow chicks climbing up the nest cup as the water floods the nest.

At around seven to eight days, the baby birds climb up on lower high tides but the data showed that climbing is not always an option during higher high tides — likely because the waters are too high for them.

“Really what is driving Saltmarsh Sparrow egg loss on high tide nights is not anything the birds are doing, but actually the high tide height alone,” Apgar said.

Nest Factors

She looked into the salt marsh bird nests to see if there were factors influencing the amount of flooding.

The factors Apgar included in models were how high the nest was off the ground, what part of the marsh it was in (high marsh zone versus low marsh zone that tends to flood more often), how high the tide height was, and elevation.

“Tide height is really driving this trend,” she reported.

Apgar also collected data at random points in the marsh to compare the nest data to the random point data to find why birds place their nests where they do.

They measured types of vegetation there, the thatch layer (dead vegetation from previous years), average height of live vegetation, elevation, and how close the nest was to the tidally influenced waterway.

“Unfortunately, I don’t have those results ready to share today. It’s to be determined. I’m still working on those models, but I hope to share those results in the future,” she said.

Apgar did share other nest-related results, though.

“Clapper Rails have greater variation in nest structure traits than Seaside Sparrows. Seaside Sparrows have greater variation in nest structure traits than Saltmarsh Sparrows. And then Willets have the smallest variation in nest structure traits,” she shared.

Apgar said that species that have greater variation in their traits tend to do better when experiencing times of change.

“So, what is my work telling us so far? All species do not exhibit a lot of adaptive capacity in relation to behavior during next flooding events … even with birds doing different things, tide heights are really driving how many offspring are lost on high tide nights,” she said.

Secondarily, the way birds structure their nests are different and that can potentially impact population trajectories.

Apgar said that these birds have done well adjusting for thousands of years, but “sea level rise from climate change is just happening really fast and my results are showing that they don’t have the capacity to deal with it on their own.”

Marsh Restoration

She mentioned that at the federal, state, and nonprofit levels, people are spending time and resources to figure out solutions to restore marshes and better deal with sea level height.

“One thing that’s being deployed is called Thin Layer Deposition. At a number of marsh sites across the coast, practitioners are adding sediment to marshes to manually increase the height of the marsh platform relative to the sea level to try to get it to not flood as much,” Apgar said.

Another strategy being implemented is the creation of ditches to drain off water that has pooled up on the marsh.

Upon concluding her presentation, Apgar then answered questions from attendees.

Upcoming Events

Connecticut Audubon Society is hosting three more Young, Gifted, And Wild About Birds online presentations:

“How Drawing and Painting Can Help You Get In Touch With The Bird World” by Jenny Kroik on March 3 at 7 pm;

“Grassland Birds Are Thriving In The Least Likely Place” by Shannon Curley, PhD, New York City Department of Parks and Recreation, and Jose Ramirez-Garofalo, PhD candidate, Rutgers University, on March 24 at 7 pm; and

“Barn Swallows Under the Light” by Murry Burgess, PhD candidate, North Carolina State University, on April 21 at 7 pm.

To sign up for the upcoming presentations, visit ctaudubon.org/2022/01/young-gifted-and-wild-about-birds-2022/.

Reporter Alissa Silber can be reached at alissa@thebee.com.