The importance of wetland margin microhabitat mosaics

The use of microhabitats for thermoregulation in wetland species is poorly studied. In their latest research, Ryeland and colleagues conduct field observations of nine species of shorebird to test whether birds selectively use microhabitats across temperatures.

Wetlands, and the species that rely upon them, are under significant threat world‐wide, and managing habitat for migratory wetland species, such as shorebirds, is particularly challenging because it requires the coordination of intercontinental efforts.

Artificial wetlands create vital habitat for migratory wetland species, particularly when returning from migration, as they need these habitats to feed and restore depleted fat and protein resources.

However, knowledge of how these species use wetland habitats at the microhabitat scale is lacking, and details of how wetland microhabitats might facilitate protection from thermal stresses has largely been overlooked.

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Wetland mosaic at Cheetham Wetlands, Victoria. Photo: Julia Ryeland

Managing daily thermoregulatory challenges

Many birds have evolved physiological and morphological adaptations to the climate in which they occur, but they must still manage daily temperature fluctuations.

Roosting in postures that cover the uninsulated appendages, e.g. the legs and bill, helps to prevent unwanted heat loss at low ambient temperatures and reduces exposure at high ambient temperatures

These postures are often used in conjunction with roost site selection, such as moving into shaded or covered microhabitats whilst roosting at high ambient temperatures and roosting in cooler microhabitats to reduce heat stress at high temperatures.

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Digiscoping’ technique for observing roosting shorebirds. Photo: Michael Weston, featuring Julia Ryeland.

In our study, we observed nine species of shorebirds under a range of temperatures and found that an important microhabitat for thermoregulation in wetland species is the cooler, water-logged substrate at the perimeter of the wetland.

Shorebirds sat on this wet substrate more at high ambient temperatures to dissipate heat across the legs to the cooler ground. Vegetated areas across wetlands were also used similarly across temperatures, likely because the insulative nature of low-density vegetation may provide more stable temperatures for long roosting bouts.

Functional wetland design

Creating and managing wetland habitats capable of supporting shorebird and waterbird species require an understanding of the functional significance of microhabitats, not only for foraging and breeding but also for roosting.

If wetland species regularly use water-logged wetland margins to reduce heat stress at high ambient temperatures, managing wetland margins is likely important in minimising heat stress in birds.

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Pied Oystercatcher sitting on the open wetland margin. Photo: Michael Weston

The ability of wetland species to manage heat stress is especially pertinent because they are threatened by both decreased wetland availability and increasing ambient temperatures under climate change.

Our study emphasises the importance of maintaining open spaces in habitat mosaics for birds to use for thermoregulation – an important consideration when restoring degraded wetlands or creating new wetland habitats

Read the full article, The importance of wetland margin microhabitat mosaics; the case of shorebirds and thermoregulation, in Journal of Applied Ecology.

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