Opportunistic airport-collision samples from swifts reveal ant nuptial flight phenology.

Ant nuptial flights are critical reproductive events, yet their environmental triggers and timing remain poorly characterised, particularly in Mediterranean ecosystems. Here we evaluate the potential of swifts (Apus apus and Tachymarptis melba) as biological samplers of alate ants using opportunistic carcasses collected after aircraft collisions at Josep Tarradellas Barcelona–El Prat Airport. By examining the oral cavities of 72 birds collected after bird strikes, ant remains were identified in 31 individuals, allowing us to assess the diversity and temporal distribution of ant flight events in the surrounding region. Sixteen ant species were detected, with Tapinoma madeirense, a species belonging to the T. nigerrimum complex, and Tetramorium forte being most abundant. Environmental variables (temperature, humidity, wind speed, rainfall) did not differ significantly between days with and without ant detections, suggesting that colony-level factors may influence flight timing. The inferred flight periods, with peaks in early morning and evening, align with heat-avoidance behaviour previously reported in several ant species but may also reflect swift foraging patterns. Most recovered alates were males, consistent with known sex ratios. This proof-of-concept study demonstrates that aerial insectivores can provide indirect information on insect reproductive phenology and highlights their potential as bioindicators for monitoring temporal dynamics of ant nuptial flights in Mediterranean landscapes.