Monitoring Bobolink stewardship

Background: A large proportion of land in southern Ontario is used for agriculture, including hayfields and pastures that provide nesting habitat for several bird species whose populations are declining. Many questions persist about how these populations are affected by farming practices and what can be done to support grassland bird conservation on farms while minimizing negative impacts on agricultural production.

Various programs provide farmers with incentives to implement best management practices intended to support grassland birds on farms (e.g., planting native grasses, installing fences to incorporate delayed grazing, delaying the hay harvest). However, more information about the impact of these stewardship actions is needed, the impact on nesting grassland birds is rarely monitored, and reliable field survey methods need to be developed.

Project work: We assessed the efficacy of low-intensity field surveys (i.e., transect surveys, point counts) to estimate Bobolink abundance and detect evidence of breeding compared to the best information available from intensive spot mapping of breeding territories and nest monitoring. We monitored Bobolink in pastures, hayfields, restored grasslands, and fallow fields. We found that two visits to transect surveys during the breeding season and distance sampling analysis provided reasonable estimates of Bobolink abundance compared to spot mapping data. We also found that transect surveys and point counts conducted in July were useful for determining when Bobolink finish breeding in fields. However, transect surveys and point counts conducted in May and June failed to accurately detect evidence of nesting and fledging of young compared to spot mapping and nest monitoring.

Conservation implications: Transect surveys and distance sampling analysis are promising methods for estimating the number of Bobolink breeding territories in an area of interest (e.g., farms enrolled in stewardship programs). Additionally, transect surveys and point counts are useful for assessing when Bobolink finish breeding in fields where agricultural activity is being delayed. These methods can be used to assess when management activities, such as grazing and hay harvest, can occur with minimal impact on Bobolink nests and recently fledged young. Transect surveys and point counts did not accurately detect evidence of nesting and fledging in May and June; therefore, if information about nesting and fledging is of interest, more intensive field methods, such as nest monitoring or spot mapping, are likely necessary.

Project dates: 2017 – 2019

Funding: Support for this project was provided by the Government of Ontario; Echo Foundation; the CICan Clean Tech Internship program; the Ontario Soil and Crop Improvement Association through the Species at Risk Partnerships on Agricultural Lands (SARPAL) program, an Environment and Climate Change Canada initiative; and individual donors.