Hematological profiles of wild birds in the central Monte Desert, Argentina: first records

Hematological parameters are widely used in avian health assessment and ecological monitoring; however, information on wild birds inhabiting the central Argentine Monte Desert is scarce. In this study, we present the hematological profiles of 172 wild birds, mainly passerines, representing 14 species from the protected nature reserves of Ñacuñán and Telteca. Birds were captured with mist nets during spring, and blood samples were taken to analyze hematocrit (HCT), total red blood cell (RBC) and white blood cell (WBC) counts, differential leukocyte count, and heterophil/lymphocyte ratio (H/L). HCT values ranged from 47 to 60 %, RBC values ranged from 2.48 to 5.88 cell × 10⁶/µL and WBC values ranged from 1.84 to 7.07 cell × 103/µL. According to the predominant leukocyte lineage, most species in this study (12 of 14) showed a lymphocytic profile, with H/L ratios generally below 1.0. In particular, the Tropical kingbird (Tyrannus melancholicus) and Common diuca-finch (Diuca diuca) showed heterophilic profiles with H/L ratios ≥ 1.0, unlike other passerines. Although low H/L values suggest minimal chronic stress, these heterophilic species may require increased caution when interpreting stress-related indicators. This study provides the first reported values for these bird species inhabiting a desert environment characterized by natural stressors but limited anthropogenic disturbance, offering valuable references for ecological, veterinary, and conservation applications.