Diversity of invertebrates within the burrows of the streaked shearwater (Calonectris leucomelas) on Toshima Island, Izu Islands, Japan

Bird nests form a unique environment that supports a diverse community of invertebrates, which is often overlooked in biodiversity studies. This study analyzed the invertebrate communities in the nests of Calonectris leucomelas on Toshima Island in the Izu Islands, Japan, confirming a total of 292 individuals. Insecta was the dominant class (49%), followed by Arachnida (28.1%), Crustacea (18.8%), Gastropoda (2.1%), Diplopoda (1.7%), and Oligochaeta (0.3%). Within the class Insecta, Coleoptera exhibited the highest abundance (97.2%), with Trox niponensis representing 82.5%. The suborder Metastigmata was identified within Arachnida. In Crustacea, Isopoda (85.5%) and Spherillo dorsalis (80%) were prevalent. Gastropoda included members of Stylommatophora and Architaenioglossa, whereas Diplopoda contained Polydesmida and an unidentified order. Oligochaeta was represented by a single species. Food habit classification revealed 40.4% as “Keratin feeders,” including T. niponensis adults and Trox larvae. “Detritivores” constituted 24%, “Blood-sucking” species in Arachnida accounted for 28.1%, and the “Other” category (1.7%) included various species. Additionally, 5.8% were classified as “Uncertain.” This comprehensive examination provides insights into the intricate relationships between C. leucomelas nests and the diverse invertebrate communities that influence nest utilization patterns and potentially impact nestling survival.