Treeline Birds

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Objective:

Increase abundance and diversity in restored treelines

Status:

Data collection in progress

Project:

Iron Curtain to Green Belt

Location:

Bulgaria

Problem: Land conversion and intensification of agriculture, including ploughing of grasslands and removal of trees and shrubs, has led to habitat fragmentation and the loss of the natural mosaic of habitats across this landscape. This leads to negative impacts on the unique fauna and flora found in treelines.

Action: The project will create 20 treelines or patches that will act as corridors and stepping stones for a wide range of species. These trees will also provide important breeding sites for threatened raptors.

Indicator: The community composition and abundance of birds will be surveyed at restored treelines to evaluate the conservation impact of this action. Data from this indicator will be combined with the indicator on treeline plants to provide a multispecies biodiversity index of changes in community.

Methods

Bird surveys will be carried out before and after treeline restoration will take place, twice per year between March and July. The first survey will be carried out in 2024, and the follow-up survey is planned for 2027.

Point counts will be used to collect data on all birds seen or heard in a five-minute interval. Twenty sampling points, with radius 150 m, will be surveyed in each habitat type (see below). The minimum distance between sampling points will be 100 m.

Because the growth of trees is much slower than the timeframe of the ELSP project, it will be difficult to detect changes in the bird community associated with the new treelines during this period. Bird surveys will therefore be carried out in pre-restoration habitats at an early successional stage (open grasslands) and target habitats in a late successional stage (restored tree lines/patches). These comparison plots will be located within 10 km of each of the restoration plots and within the project area. Comparing the bird communities across each of these habitat types will allow the project to demonstrate the biodiversity change that can be expected after treeline restoration, and track the restoration sites’ progress as they hopefully approach the target condition.