Supplemental Hollows

Natural hollows typically form in mature trees over many decades or even centuries. These hollows are lost when old trees are removed due to urban development, risk management, agriculture, or logging. The loss of hollows threatens the survival of hollow-dependent species.

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A pressing question in conservation science is whether supplemental hollows—such as artificial nest boxes or carved hollows — can replace natural hollows.

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Supplemental hollows may provide immediate shelter and nesting sites for species that would otherwise struggle to find suitable habitats. This could be particularly crucial in fragmented landscapes, where isolated patches of habitat may lack mature trees. In urban and suburban areas, supplemental hollows may play a role in maintaining biodiversity by supporting native wildlife populations amidst human development.

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However, it's important to implement these solutions thoughtfully. Well-designed and properly installed supplemental hollows hope to mimic the thermal and structural conditions of natural ones, ensuring they are suitable for target species. In contrast, poorly deployed or maintained supplemental hollows can become hazards, increasing the risk of predation, overheating, or disease. In addition, supplemental hollows could have the unintended consequence of attracting and supporting only pest species.

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Thus, we need more information about what makes supplemental hollows effective at supporting target wildlife. If effective, supplemental hollows could be a valuable tool in biodiversity conservation when habitats are modified or degraded. In addition, they may help bridge the gap while younger trees mature and begin to develop natural hollows.

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In this project, we are partnering with Randwick City Council and Greater Sydney Parklands in Sydney, Australia, as they trial supplemental hollows within an urban landscape. We aim to examine the efficacy of these habitats to support target native wildlife and bolster local populations.