Ecological and behavioral dimensions of coexistence in two understory babblers in Subtropical China

Species coexistence is pivotal for ecological balance and is shaped by resource dynamics and evolutionary processes. It is generally believed that a certain degree of niche overlap is beneficial for the integrity and efficiency of mixed-species foraging flocks (MSFs) in birds, whereas the coexistence of species requires niche divergence as a fundamental prerequisite. To navigate the paradox of coexistence against the backdrop of MSFs is crucial for understanding avian biodiversity. Here, we took the angle from home ranges to address this question. VHF telemetry tracking was conducted on two widely coexisting understory birds of the mixed-species flocks, the David's fulvetta (Alcippe davidi) and the Streak-breasted scimitar babbler (Pomatorhinus ruficollis) in subtropical Central China to investigate their spatial interactions during breeding season. Our research revealed significantly greater intraspecific home range overlap (0.376) in the fulvettas than in the scimitar babblers (0.213), which suggests differentiation in intraspecies gregariousness. Further scrutiny of habitat preferences revealed that scimitar babblers had significantly high tolerances to barren lands and croplands. Both species maintained similar home range sizes and foraging timings and paces. Our research underscores the importance of intrinsic gregariousness and convergent land cover type preferences in MSFs albeit other diverging characteristics in the breeding season.