The Audubon series depicts the combat of salt marsh birds with high tide

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

Sam Apgar led the High Tide for Salt Marsh Birds program to show how salt marsh birds experience nest flooding due to high tides.

According to Connecticut Audubon Communications Director Tom Andersen, “Sam is a graduate student at the University of Connecticut 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 on her dissertation work and what has been learned so far.

She shared: “No research takes place in a vacuum. There are many different groups that have either funded my work or provided me with access to the site to do my work and collect my data. Regarding the field teams, undergraduate volunteers and independent undergraduate students helped me collect and analyze the data.”

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

“Another really important thing about tidal marshes is that they’re tidal,” Apgar said. “Every day there are two high tides and two low tides, and around the new moon or full moon you have higher tides. So the extent to which the swamp floods inundate is determined by a lot of factors, but the moon is really driving it quite a bit.”

With this in mind, birds that nest on the ground in these swamps will inevitably experience some form 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 high tide.

“Although it seems quite intense, these birds have been dealing with these conditions for a long time. These species have lived and reproduced in swamps for thousands of years, so they have some tools to deal with some nest flooding,” Apgar said.

She highlighted the salt marsh sparrow, which nests in swamps, noting that there is research showing the bird species is in rapid decline due to sea level rise and other factors.

“The Saltmarsh Sparrow specifically is declining at a rate of 9% per year, which is the largest decline of any species studied,” Apgar reported.

Why the decline?

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

“For the most part it has been established that Salt Marsh Sparrows are unfortunately unable to fledge enough chicks because the nests are flooded – either the eggs become flooded during the egg stage or the chicks drown at the chick stage and are unable to successfully exit the nest… Extinction is on likely for this species,” Apgar said.

However, she reported that other birds nesting in salt marshes show different data trends.

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

Apgar investigated why the salt marsh sparrow is in decline the most compared to other similar species that nest in salt marshes, even though they are all dealing with the same stressors.

She used infrared video cameras at two locations on the Connecticut coast — Hammonasset Beach State Park and East River — to study how the birds responded to nest flooding at night and whether it affected their fate during flooding.

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 the chicks were born, whether the nest was wet or not.

For Willets, she showed accelerated video of three eggs in a nest beginning to swim as the water flooded the nest. Two eggs eventually began to drift out of the nest cup area.

“This video is emblematic of many species, but willets in particular. They really don’t spend much time in nests when they’re inundated,” Apgar said. “Clapper rails, on the other hand, spend slightly more time than the other species in the nest when flooding.”

She then shared a video showing an adult Clapper Rail using its beak to maneuver around blades of grass while the nest was flooded to prevent eggs from flooding out. She noted that in some cases other studies have shown that clapper rails go out and retrieve the eggs that have been flooded from the nest.

Apgar also spoke about nestlings and shared video of Saltmarsh Sparrow chicks climbing the nest cup as the water floods the nest.

At around seven to eight days, the chicks start climbing at lower tides, but data showed that climbing at higher tides isn’t always an option — likely because the water is too high for them.

“What really drives Saltmarsh Sparrow egg loss on high tide nights isn’t something the birds do, it’s actually tide height alone,” Apgar said.

nest factors

She looked into the bird’s nests of the salt marshes to see if there were any factors affecting the extent of the flooding.

The factors that Apgar included in the models were how high the nest was above the ground, what part of the swamp it was in (high swamp zone versus low swamp zone prone to flooding more often), how high the tide was high and the high.

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

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

They measured vegetation types, thatch cover (dead vegetation from previous years), average height of living vegetation, nest height and proximity to the tidal waterway.

“Unfortunately, these results are not available to me today. It is to be determined. I’m still working on these models, but I hope to be able to share these results in the future,” she said.

However, Apgar shared other Nest-related findings.

“Clapper Rails have greater variation in nest structure characteristics than Seaside Sparrows. Sea sparrows exhibit greater variation in nest structure characteristics than do salt marsh sparrows. And then willets have the smallest differences in features of nest structure,” she shared.

Apgar said that species that show greater variation in their traits tend to do better when they experience times of change.

“So what does my work tell us so far? All species don’t show much adaptability in terms of how they behave in the next flood…even if birds do other things, tide heights really determine how many offspring are lost on flood nights,” she said.

Second, the way birds structure their nests varies, which can potentially impact population trends.

Apgar said these birds have adapted well for thousands of years, but “sea level rise from climate change is just happening very quickly, and my results show that they are unable to cope on their own.”

Swamp Restoration

She mentioned that people at the federal, state, and nonprofit levels are investing time and resources to find solutions to restore swamps and better deal with sea level elevation.

“One thing that is used is called thin layer deposition. At a number of swamp areas along the coast, practitioners are adding sediment to the swamps to manually increase the height of the swamp platform relative to sea level to try not to flood them as severely,” Apgar said.

Another strategy being implemented is the creation of ditches to drain water that has accumulated on the swamp.

After completing her presentation, Apgar answered attendees’ questions.

Upcoming Events

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

‘How drawing and painting can help you get in touch with birdlife’ by Jenny Kroik on 3 March at 7pm;

“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, graduate student, Rutgers University, March 24 at 7 p.m.; and

“Barn Swallows Under the Light” by Murry Burgess, graduate student, North Carolina State University, April 21 at 7 p.m.

To register for upcoming presentations, please visit

Reporter Alissa Silber can be reached at [email protected].

Sam Apgar’s February 10 presentation, “High Tide for Salt Marsh Birds,” focused on how rising sea levels are affecting Saltmarsh Sparrows, Clapper Rails, Willets and Seaside Sparrows, all of which nest in Connecticut’s tidal marshes.

Sam Apgar shared video footage of birds nesting in salt marshes at night, including the one pictured with three eggs visible.

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