Seed dispersal is the movement of seeds away from parent plants, usually mediated by abiotic or biotic agents. Most Arisaema species (Araceae) bear bright orange-red fruits in autumn. We investigated the fruit removal of a poisonous herb Arisaema serratum by using cameras for three years, and identified the quantitatively effective seed dispersers in two study sites in central Japan. Furthermore, we conducted germination experiments of seeds dispersed by two bird species Hypsipetes amaurotis and Turdus pallidus, both of which were identified as quantitatively effective seed dispersers of A. serratum. The study was conducted in a cedar plantation of the Forestry Experimental Station, Ishikawa Agriculture and Forestry Research Center, and at a second forest site at the Satoyama Zone, Kanazawa University, Ishikawa Prefecture, central Japan. By conducting camera-trapping at 60 fruiting individuals of A. serratum (11 plants in 2013, 20 plants in 2014, and 29 plants in 2015), we identified the frugivore assemblage that foraged on the fruits and quantified the number of visits and the number of fruits eaten on each visit. The top three bird species with the highest frequency of visitation were 180 times (47%) by T. pallidus, 118 times (30%), by H. amaurotis, and 40 times (10%) by Luscinia akahige. The top three species with high fruit consumption were 573 fruits (31%) by H. amaurotis, 481 fruits (26%) by T. pallidus, and 98 fruits (5%) by Zoothera dauma. The germination rates of seeds were 100% (N=129) for the seeds carried by H. amaurotis, 98.8% (N=163) for T. pallidus, and 97.1% (N=834) for controls, with no significant differences. The high number of visits to fruiting plants and fruit removal rates by H. amaurotis and T. pallidus for three years at two different study sites led us to the conclusion that they show high effectiveness in terms of quantity of seeds dispersed for A. serratum. Furthermore, both bird species were likely to be qualitatively effective seed dispersers because they disperse intact seeds within tens of meters in the appropriate habitats.

To clarify the feeding habits of Osprey Pandion haliaetus in coastal areas of Iwate Prefecture, we set a camera in two nests during the breeding season of 2018 and analyzed the prey items recorded. We identified fishes to family or order levels, measured their total length, and estimated their weights based on values reported in the literature. In the two nests, Beloniformes was the most frequently observed order, and Scombridae, Cyprinidae, Carangidae, and Mugilidae were also delivered frequently to the chicks. The families of fishes that had the highest estimated weights were Scombridae and Mugilidae, suggesting that they are important food resources for chick growth. Many of these fishes live at the sea surface, in shallow water, or in mild currents, which corresponded to the known hunting behavior of Osprey, which hunt fish swimming near the water surface. The Osprey in this study fed on seasonally available saltwater fish, with the exception of Carp families. Of Carp, Tribolodon and Carassius, which inhabit the freshwater and marine coastal areas, respectively, were major prey items delivered to osprey nestlings. The estimated weight per feeding was significantly larger in both pairs during the late rearing period. Based on the habitat characteristics of the fish that Ospreys delivered to the nest, the bays and estuaries were the main fishing areas. At present, there is a concern about the deterioration of the fishing habitat for Ospreys, due to the reconstruction project after the major Tohoku Earthquake in 2011.

The Striated Heron Butorides striata is a nearly cosmopolitan species except for North America. Available information on the breeding biology is scarce, including breeding success. I studied the species’ preferred nest-tree species, the number of breeding pairs, and the breeding success of this heron in an urban park of Utsunomiya, central Japan, from 2012 to 2019. The aim of this study was to collect basic data about the breeding biology of this heron species, and to observe the relationship between changes in nest-tree species and breeding success. The number of heron pairs gradually increased from five to twelve pairs from 2012 to 2016, but thereafter decreased from seven to five pairs. A total of 113 nests were observed during the survey period, and the number of fledglings per nest varied significantly among survey years. The nests were built on high branches, averaging 17 meters above the ground. The heron preferred Cedar Cedrus deodara as nest-trees from 2012 to 2014. From 2015 to 2019, most of the nests were built on the Zelkova Zelkova serrata, and breeding success decreased during this time. With the change in nest-tree species, nesting sites were gradually moved within the park. The author recorded the cases of predation by Large-billed Crows and by mammals, as well as nests being blown down by strong winds. In most cases, however, the cause of breeding failure was unknown.

Birds are known to respond to climatic factors such as ambient temperature and day length. In the context of global climate trends, understanding a bird species’ response to the local temperature is a basic ecological factor that has conservation value. As an index to determine the start of the breeding season for the Japanese Bush Warbler Cettia diphone, we created a model based on effective accumulated air temperature to predict the date of the species’ first song of the spring season. From the “Seasonal Front Watch” data set of the Japan Bird Research Association, we used recorded date of the species’ first song at 39 monitoring sites during the period of 2005 to 2019. For each recorded date of the first song, we calculated the effective accumulated air temperature within 80 km of the monitoring site. We then developed a model to predict the first song date in all parts of Japan by obtaining the equation for the relationship between the effective accumulated temperature and the average temperature at each monitoring site. We validated the model by using the date of the first song in 2020, and found that it predicted the date of the first song of the Japanese bush warbler better than the average date of the first song over the period from 2005 to 2019. The result indicated that the effective accumulated temperature is an accurate method to predict the date of the first song of the warbler.

A change of distribution for birds in Hokkaido is evident from results of the National Surveys on the Natural Environment (the report of the distribution of Japanese birds) between 1974-1978 and 1998-2002. As a series of nationwide reports, the published distribution maps were not suitable for showing regional patterns, so I analyzed the data on range changes of each bird species in Hokkaido, the northernmost region of Japan. Range reductions were observed for some, but not all, summer migrant birds, and severe range reductions were confirmed in particular species. Resident birds, on the other hand, experienced fewer range reductions, and a higher frequency of range expansions. Summer migrant birds showed range reductions in several habitat types, including grasslands, rural areas, and woodlands. The species that showed range expansions primarily inhabited woodlands, whereas those inhabiting grasslands and rural areas had low frequency of expanded ranges. A severe range reduction was observed for three species: White-throated Needletailed Swift Hirundapus caudacutus, Brown Shrike Lanius cristatus, and Yellow-breasted Bunting Emberiza aureola. Oddly, the range of Ruddy Kingfisher Halcyon coromanda, which showed a nationwide range expansion, had a range reduction in Hokkaido. Range reduction was not confirmed for four species that have been reported in previous studies, namely Latham's Snipe Gallinago hardwickii, Bull-headed Shrike L. bucephalus, Eurasian Skylark Alauda arvensis, and Eurasian Tree Sparrow Passer montanus. Further study of ranges and population trends for birds in Hokkaido is recommended, as the data shows there have been numerous changes in the distribution of birds in the region.

Egg predation on ground nesting birds by Ruddy Turnstones Arenaria interpres has been recorded in the other countries, but not in Japan. We directly observed and video-recorded Ruddy Turnstones in the act of predating eggs of Little Terns Sternula albifrons at two sites. We assume that this behavior is not common, and may be expressed only by a few particular individuals, but considering the safety of endangered species such as Little Terns, we may need to take measures against the egg predation by turnstones.

To determine the timing of the Kamchatka Leaf Warbler Phylloscopus examinandus migration, I conducted bird observations at a park in Asahikawa, Hokkaido, about five times a week during the spring migration period from 2017 to 2020. I found that the timing of the Kamchatka Leaf Warbler migration varied from year to year, but that warblers were most frequently recorded in late May and early June, and rarely in late June. Furthermore, the Japan Bird Research Association’s database were reviewed, and included records of 73 Kamchatka Leaf Warblers observed in Hokkaido from late May to mid-June. Because of the late migration by Kamchatka Leaf Warblers, it was difficult to judge whether the birds were observed while still on migration, or if they may have been in Hokkaido for breeding. Our result suggests that observation of Kamchatka Leaf Warblers after late June suggests a strong possibility of breeding, if observations are recorded in suitable breeding habitat. In such cases, an intensive investigation may confirm the presence of breeding.