Distribution of Arthropods in the Burrow and Nest of Sand Martin (Riparia Riparia (Linnaeus, 1758)) (Aves: Passeriformes) in the Northern Part of the Lower Volga Region

The research conducted on the territory of Saratov oblast in the Khvalynsky district, from 2020 to 2023. Between 2020 and 2022, arthropods were manually collected from burrows, while in 2023, the method of trap-cylinders was used. The latter method was utilized to study three colonies of sand martins (Riparia riparia) located in the villages of Demkino, Apaliha and Kulatka. Nest material was extracted from burrows during excavation, placed in individual zip-lock bags labeled for transportation, and placed on a Tullgren funnel. The results revealed a total of 4873 arthropod specimens belonging to 21 orders were collected. Specifically, 3,799 specimens were collected from nests and 1,074 specimens were obtained from burrows (using trap-cylinders). Different years exhibited varying dominant orders of arthropods in nests and burrows. Thus, the order Coleoptera were dominant in nests in 2020 and 2021, and Mesostigmata predominated in 2022 and 2023. Conversely, Diptera was the dominant group in burrows, with Coleoptera and Mesostigmata serving as subdominant and recedent groups, respectively. Calculation of the biotope confinement index showed that nest and burrow had their own characteristic complex of arthropods, in nest the dominant groups included Mesostigmata, Sarcoptiformes, Poduromorpha, Entomobryomorpha, Thysanoptera, Coleoptera, and Siphonaptera, while in burrows, the predominant groups comprised Opiliones, Trombidiformes, Araneae, Hemiptera, Hymenoptera, and Diptera. It was determined that free-living species (representatives of the families Phoridae, Muscidae, and Drosophilidae) dominated in burrows, with no association to either the nest or the nest owner, accounting for 80% of the total abundance. The dominant assemblages in nests consisted of three species (Androlaelaps casalis, Tetramorium sp., and Haploglossa nidicola), which were prevalent across most colonies. Groups that dominated in burrows were either recedents and/or subrecedents in nests or entirely absent, suggesting a buffering role of the burrow that acts as a barrier to the movement of flying insects. Due to the isolation of nest-dwelling communities containing eudominants, the overall species abundance and alpha diversity of arthropods in the nests and burrows in sand martin nests were found to be notably low.