Presence of Cuckoo reliably indicates high bird diversity: A case study in a farmland area

•The occurrence of Cuculus canorus was evaluated as indicator of biodiversity.•Generalized Linear Mixed Models were applied on bird data collected in four years.•Cuckoo is 27% more effective than using top predators.•Cuckoo is a superior bioindicator: charismatic, widespread and easy to detect.•Our findings provide a new effective and cheap tool to monitor the biodiversity. Here we studied the occurrence of Cuckoo Cuculus canorus and top predators as indicators of biodiversity in agro ecosystems of Western Poland, to identify local hotspots. Bird species richness and land-use diversity were used as measures of biodiversity. The relationship between the presence of Cuckoos and four avian top predators with biodiversity measures were examined using Generalized Linear Mixed Models. Cuckoos were mainly distributed on sites with greater species richness, but were absent from the low species richness sites, while the top predators were distributed uniformly. The performance of the best models using the presence of Cuckoo was 27% higher than the best models using top predators. Our results highlight the predictive capacity of Cuckoos as an indicator of bird species richness than top predators and the usefulness of this species in biodiversity studies. The cookoo is charismatic, widespread across the main types of landscapes, and is easy to detect from its song. Importantly, our findings propose that cookoo can be used as effective and cheap tool to monitor the high bird diversity in different European countries.