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Doctoral defence: Triin Kaasiku “A wader perspective to Boreal Baltic coastal grasslands: from habitat availability to breeding site selection and nest survival”

On 24 May at 14:15 Triin Kaasiku will defend her doctoral thesis “A wader perspective to Boreal Baltic coastal grasslands: from habitat availability to breeding site selection and nest survival” for obtaining the degree of Doctor of Philosophy (in Zoology and Ecology).

Supervisor:
Associate Professor Riinu Rannap, University of Tartu

Opponent:
Lecturer Veli-Matti Pakanen, University of Oulu (Finland)

Summary
Semi-natural grasslands, where low-intensity agricultural activities that imitate natural disturbances have created ecosystems for millennia, are a prime example of the rare positive anthropogenic effect on biodiversity. However, as these habitats are usually marginally productive, they are currently endangered by either intensified or ceased management. A species group often dependent on semi-natural grasslands is waders – threatened ground-breeding birds adapted to breed in open landscapes. Primarily as a result of habitat loss and low reproduction rates, they are going through substantial population declines both in Europe and globally, making them one of the most threatened groups of birds. This thesis focuses on a semi-natural wet grassland– the Boreal Baltic coastal grassland – which in Estonia hosts protected plant species, amphibians, and birds, including waders. Similarly to other types of semi-natural grasslands, ca. 90% of the coastal grassland habitat was lost in Estonia during the last century, mostly as a result of land abandonment. However, since the 1990s steps towards improving the coastal grassland habitat have been taken, including an active restoration programme and continuous agri-environment scheme-supported management. Nevertheless, the threatened wader populations dependent on this habitat have not recovered, raising the concern whether the currently fragmented landscape still holds suitable conditions for breeding waders. The issues faced by the breeding wader community on Boreal Baltic coastal grasslands were investigated in this thesis, concentrating on habitat availability, important habitat features, nest survival, and predator community. For the first time, it is shown that the agri-environment scheme applied on coastal grasslands increases the availability of suitable habitat for breeding waders in terms of vegetation height. Waders need access to wet features and as open habitat specialists prefer wide intact areas, while avoiding forest edge. The probable reason behind the avoidance of forest is driven by the higher nest predation rates by the red fox at the proximity of woodland. However, nest survival rates remain low even furthest from the forest, questioning the viability of the wader community breeding on coastal grasslands. While nest predation is a serious issue, a novel predator with a quickly expanding range, the golden jackal, does not seem to add pressure on wader nest survival in this habitat. Lastly, as a methodological finding, it is shown that artificial nests are not an adequate alternative to wader nests when studying nest survival in this habitat. The results of this thesis inform nature conservation actions that have the potential to improve the state of breeding wader populations in the coastal grassland habitat.

The defence will be held also in Zoom: https://ut-ee.zoom.us/j/96775218881?pwd=OWVnZ2ZWcFp6OXhLY3JvR2I4VDBZZz09. Meeting ID:967 7521 8881, password: 294272.

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