31-23 Hydrologic and Geologic Influences on a Wetland Habitat of Native Hawaiian Birds

Session: Environmental Geochemistry and Health (Posters)

Poster Booth No.: 49

Presenting Author:

John Quinn

Authors:

Quinn, John J.¹, Walston, Leroy², LaGory, Kirk³, Benda, Christopher⁴, Beard, Emma⁵, Gagnier, Marie⁶, Zill, Julie⁷

(1) Argonne National Laboratory, Argonne, IL, USA, (2) Argonne National Lab, Argonne, IL, USA, (3) Argonne National Lab, Argonne, IL, USA, (4) Argonne National Lab, Argonne, IL, USA, (5) Colorado State University, Center for Environmental Management of Military Lands, Ft. Collins, CO, USA, (6) Bellows Air Force Station, Waimānalo, HI, USA, (7) Colorado State University, Center for Environmental Management of Military Lands, Ft. Collins, CO, USA,

Abstract:

Avian foraging and nesting activity in a coastal wetland may vary with hydrologic conditions operating at various timescales. At the Pu‘ewai Wetland on the windward side of eastern O‘ahu, endangered ae‘o (Hawaiian stilt) and ‘alae ‘ula (Hawaiian gallinule) are commonly present. The wetland, at Bellows Air Force Station, is alongside the Waimānalo Stream (locally referred to as Puhā Stream) and within 250 m of the Pacific Ocean. The water level in the wetland often fluctuates diurnally with the tide. However, coastal sedimentation processes can create a sand plug at the mouth of the stream, separating the wetland from the tidal flushing effect.

Since 2021, the natural hydrological dynamics of the wetland have been studied by collecting hourly water level data using probes at three surveyed locations. These data are accompanied by hourly photos using programmable cameras to obtain visuals of the wetland conditions and sand plug.

Results indicate the depth, duration, and seasonality of flooding due to a sand plug; the occurrence of either dry, stagnant conditions or freshwater flooding behind a sand plug; and the magnitude of tidal fluctuations in the absence of a sand plug. These hydrologic scenarios are compared to bird activity observations to assess the relationship.

This study serves as a complement for long-term avian and vegetation surveying of the Pu‘ewai Wetland. Altogether, the studies aim to analyze the ability of the wetland to provide ground-nesting and foraging habitat for the species of concern and identify possible management considerations.

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