Crows and sparrows are familiar birds in Japan. Experiences with these species during daily life lead to people having both positive and negative feelings toward them. We analyzed newspaper articles available at the online database of Asahi Shimbun Kikuzo II Visual to assess how attitudes towards crows and sparrows have changed over time. Of the total number of search results, since 1990, we found that articles about crows accounted for 0.08% and sparrows accounted for 0.04%. Negative attitudes were more marked in articles about crows, while positive or favorable attitudes were relatively dominant in articles about sparrows. The trend was greater in 2015–2016 than in 2000–2001.
Many insects have been identified in bird nests, and the birds have been considered as serving as ecosystem engineers creating habitats for insects. However, few ecological studies have demonstrated this link between birds and insects. We investigated whether avian breeding activities provide habitats for insects, and whether insects positively utilize bird nests, by investigating Japanese Tits Parus minor using nest boxes over three years. We found that the occurrence of keratin-feeding insects was positively correlated with the length of the periods the birds used the nests (i.e. from the day of first egg laying to fledging, predation or desertion day). Detritivores insects showed the same tendency. These results suggest that avian breeding activities provide new habitat not only for keratin feeders, which are thought to depend on feather sheath debris, but also insects that feed on humus. When nest materials collected immediately after birds had finished using their nests were compared with those material collected three weeks later, there was no difference in the frequency of the generation of insects regardless of their food habits. This result indicates that insects invade nests before birds finish breeding.
Long-term monitoring of a long-established Great Cormorant colony was conducted during 1980–2020 and a large-scale census of cormorant colony distribution during 2015–2020 was conducted in Aomori Prefecture, north Japan. This research has revealed relationships between fluctuating nest numbers and the timing of new colony establishment. The long-standing colony experienced increases in nest numbers. The size of colony decreased a year or two after reaching maximum size, then recovered. These cycles were repeated four times during the study period. New colony establishment followed nest decrement at the main colony during 2009–2011, and 10 new colonies had been founded by 2020. This indicates that nest decrement and natural dispersal of breeding individuals from the main colony were the likely triggers for the establishment of new colonies.