CCB and Saltmarsh Bird Surveys

A frozen marsh on the eastern shore of Virginia.

Saltmarsh Sparrows Surviving Virginia’s Winter Weather

March 29, 2023

Menhaden added to an osprey nest on Mobjack Bay.

Recent literature published by CCB

July 8, 2023

Published by Center for Conservation Biology at June 1, 2023

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saltmarsh sparrow

CCB field technician, Riley Strasbaugh, trudges through a black needlerush marsh towards a survey point on Virginia’s Eastern Shore. Needlerush marshes have become more common on the eastern shore since the mid-20th century and the species that are more likely to use these patches for nesting remain relatively common while others have declined precipitously. Photo by Chance Hines.

By: Chance Hines
5/30/2023

Center for Conservation Biology researchers have a long history of trudging through coastal marshes studying a variety of bird taxa including shorebirds, wading birds, and songbirds. The terrain is often difficult to traverse due to muddy tidal guts that can swallow you whole, needlerush that pierces skin with every step, and swarms of insects eager for human flesh. Despite these discomforts, CCB biologists find pleasure in the solitude when they reach remote marsh patches few others are willing to access.

Among studies CCB has conducted within this landscape, a key survey during the early 1990’s established a baseline for bird communities found in marsh patches along the western shore of Virginia’s Chesapeake Bay. The bird communities during the early 1990’s included a rich suite of marsh obligates as well as facultative species. A 2021 follow up survey of these same marshes revealed that nearly all species during the baseline survey were less likely to occupy those areas and several species had all but disappeared. Among the species that had declined most precipitously in these marshes were saltmarsh sparrow, sedge wren, eastern meadowlark, and song sparrow while red-winged blackbird was the only marsh-obligate species that did not decline.

Occupancy for groups of marsh-nesting birds during the initial survey of western shore marshes in 1992 and the follow up survey in 2021. All groups of birds were less likely to occupy marshes but the decline was most noticeable for facultative marsh nesters. Figure by CCB.

Following the findings of the 2021 survey on the western shore of the Chesapeake Bay, CCB initiated a two-year study in partnership with the Virginia Institute for Marine Science surveying marshes along Virginia’s more rural eastern shore. This study is focused on the comparison between marsh patches that existed prior to the mid-20^th century and have withstood rising sea levels with those that have converted to saltmarsh from upland forest and agricultural fields since the mid-20^th century.

Example of a short grass saltmarsh patch that has persisted since prior to the mid-20th century. These portions of the marsh include the short form of smooth cordgrass, saltgrass, and saltmeadow hay with pockets of black needlerush and small pools of water. Photo by Chance Hines.

Example of a marsh patch that has converted from upland habitat. The linear water feature is a former agricultural irrigation ditch which may alter the natural tidal flow and allow species that are less tolerant of saline conditions, like phragmites and black needlerush to dominate the plant community. Photo by Chance Hines.

The initial 2022 field season revealed that some marsh-nesting species were less likely to be found in the more recently created marsh patches. It is not clear what drives this difference, but land practices prior to marsh conversion may affect habitat quality of the newly formed marshes. Marshes that were formerly agricultural fields supported lower occupancy of several species including those that are most commonly encountered in saltmarshes like seaside sparrows and clapper rails, but findings were less clear for some species like saltmarsh sparrows which were recorded at relatively few of our survey points.

CCB lead field technician, Maddie Was, surveying an island marsh patch during the 2023 survey season. Many of these marsh patches are only accessible via boat. Photo by Chance Hines.

The second year of the study includes a wider array of marsh patches, including locations that can only be accessed via boat. We hope these additional survey locations provide more accurate estimates of occupancy and abundance for species like saltmarsh sparrows, which avoid mainland edges.