Is the Northern Goshawk an Efficient Bioindicator of Avian Abundance and Species Richness in Urban Environments?

Monitoring of biodiversity in expanding urban areas is an essential part of wildlife conservation. There is evidence that raptors, such as Northern Goshawks (Accipiter gentilis), are effective bioindicator species in urban areas, however, their relationship with other bird populations is not clearly established. We asked whether activity patterns of Goshawks are a reliable indicator of wintering bird abundance and diversity in urban ecosystems. We tracked the movement of eight GPS-tagged Goshawks in the city of Tartu (Estonia) and analysed the numbers and diversity of birds in the same area using direct mapping and occasional data obtained from birdwatchers. The direct mapping approach revealed that the number of birds and avian species richness were higher in Goshawk activity hotspots than at random sites in 2022, however, no such differences were detected in 2023. Analysis of occasional citizen-collected data showed no effect of avian abundance nor species richness on the distribution of Goshawk activity. These results suggested that the movements of Goshawks may indicate the abundance and diversity of its prey, however, this relationship depends on the detection methodology. Hence, raptors are a promising bioindicator in urban environments, but results should be interpreted with caution, particularly when using citizen-collected data.

Automated summary

Monitoring biodiversity in expanding urban areas is crucial for wildlife conservation. Raptors, like Northern Goshawks, are potentially effective bioindicators in such areas, but their relationship with other bird populations needs further investigation. This study examined whether Goshawk activity patterns could reliably indicate bird abundance and diversity in urban ecosystems. Tracking eight GPS-tagged Goshawks in Tartu city (Estonia) and analyzing bird numbers and diversity using direct mapping and citizen-collected data, the results showed that Goshawk activity hotspots had higher bird abundance and species richness in 2022, but not in 2023. Furthermore, occasional citizen-collected data did not correlate with Goshawk activity. These findings suggest that Goshawk movements may reflect prey abundance and diversity, but caution should be exercised when interpreting results, especially with citizen-collected data.