Using long-term citizen science data to understand distribution and habitat use of an irruptive species

Unpredictable movement patterns of irruptive migrants make them difficult to study through structured survey methods. We used citizen science data to assess the distribution and habitat usage of an irruptive migrant outside its core area of occurrence. We curated 50 years of citizen science data on Red crossbills (Loxia curvirostra) in Arkansas and field observations to 1) assess their distribution and habitat use outside their core area of occur-rence, 2) determine if Red crossbills breed in Arkansas, 3) characterize the occurrence and abundance of Red crossbills in Arkansas, and 4) identify call types or ecotypes of Red crossbills present in Arkansas during 2017-18 irruption. We constructed a sample bias-corrected species distribution model using elevation, land cover type, and monthly temperature and precipitation as predictors for MaxEnt algorithm. The most significant predictors of Red crossbill distribution were land cover type, elevation, and precipitation of October. The probability of Red Crossbill occurrence was high in developed areas, areas with large water bodies, open areas, and evergreen forests. Red crossbills were found to breed in Arkansas based on field observations and historical records. The time-series captures the major irruption years within last 50 years in Arkansas. It also depicts months when the probability of finding Crossbills in Arkansas is highest. In addition, we documented four call types or ecotypes of Red crossbills in Arkansas, including type 1 and 4 that were previously unreported. Our study illustrates utility of citizen science observations for understanding the occurrence, distribution, and habitat use of difficult to study nomadic species.

Automated summary

Through the use of citizen science data and field observations, this study assessed the distribution, breeding patterns, and habitat usage of Red crossbills in Arkansas, revealing their presence in developed areas, areas with large water bodies, open areas, and evergreen forests. The study also identified four call types or ecotypes of Red crossbills, including previously unreported types 1 and 4.