Factors Influencing Prevalence and Intensity of Haemosporidian Infection in American Kestrels in the Nonbreeding Season on the Baja California Peninsula, Mexico

Abstract

ABSTRACT Overwintering areas can act as reservoirs for haemosporidians, and their blood-sucking vectors may easily survive and flourish in warm climates. The American Kestrel (Falco sparverius) is a small-sized raptor that includes both resident and migratory individuals that overwinter in agriculture areas of the Baja California peninsula, Mexico. We measured and collected blood samples from 54 individual kestrels captured in a fragmented habitat located within a matrix of agricultural and native scrub in the southern part of the peninsula during the autumn and winter of 2018–2019 and 2019–2020. We identified and quantified haemosporidians in blood smears of each individual. We used decision tree classification models of prevalence and intensities of haemosporidians to assess the importance of season, host body size, and environmental characteristics of the capture site (proximity to the nearest infected host, number of ponds used for irrigation, Normalized Difference Vegetation Index [NDVI], distance to the edge of the agricultural matrix, and distance to the nearest city). Overall prevalence was 42.6%, with an average intensity of 2.4 haemosporidian-infected cells per 2000 erythrocytes. Most haemosporidians (91.3%) were identified as Haemoproteus tinnunculi, and the rest as Plasmodium spp. The prevalence of haemosporidians increased with pond availability, the distance from the edge of the agricultural matrix, and the proximity of infected individuals. Parasite intensity increased with the availability of ponds, the distance to the edge of the agriculture matrix, and the NDVI. Spatial and temporal patterns of parasite prevalence and intensity illustrated local infection dynamics, suggesting a complex scenario of haemosporidian transmission in migratory and resident kestrels.