Leaf shelters indirectly mediate interactions in animal-plant communities by providing the occupants with several kinds of benefits, as physical ecosystem engineering. The occupants benefit from favorable microhabitat, reduction in antiherbivore defense, and protection from natural enemies. The primary shelter maker has to spend energy and time and producing silk, but shelter users have great advantages without incurring costs. Shelter users consist of a wide range of arthropod taxa and can be divided into two groups: coexisting organisms that live with a primary shelter maker in the same shelter, and secondary users, which inhabit a leaf shelter after it is utilized by a shelter maker. Leaf shelters mediate interactions between (1) primary shelter makers and coexisting organisms or (2) primary shelter makers and secondary users, (3) secondary users, (4) shelter users and their natural enemies, and (5) primary shelter makers, secondary users, and their host plants. Most interactions between primary shelter makers and coexisting organisms constitute a direct trophic linkage rather than indirect ones. There are actually unidirectional beneficial effects from a primary shelter maker to secondary shelter users, whereas leaf shelters mediate competition and predation among shelter users. By providing a leaf shelter, a shelter maker leads to increased diversity of interactions. Leaf shelters modify the distribution of organisms on the host plant and influence herbivory on the host plant. In tritrophic interactions, leaf shelters act as cues for natural enemies that search for a shelter user as prey. Furthermore, by enhancing habitat heterogeneity, leaf shelters affect the abundance and species richness of arthropods on host plants.

The role of the brown‐eared bulbul, Hypsypetes amaurotis, as a dispersal agent for seeds of fruiting plants was studied by field observations for two years, in parallel with laboratory experiments on seed germination. Bulbuls consumed fruits of 53 species from 24 plant families. The fruits of these plants had similar color and size, and these characteristics were likely to enhance the feeding efficiency of the frugivore. Laboratory experiments on 20 food plant species demonstrated that: (1) no seeds were injured by passing through the bulbul's gut; (2) seeds that had passed through the bulbul's gut were still able to germinate and (3) fruit pulp reduced germination ability. When pulp was removed by passing through bulbul's gut, or by hand, germination was improved. An estimate of the home range of six bulbuls suggested that they may transport seeds for at least 300 m.

Mutual interactions between birds and plants species have been emphasized in a range of studies of endozoochory, during which frugivorous birds consume fruit and subsequently disperse plant seeds (Snow 1971;Herrera 1985Herrera , 1995Jordano 1995). There are, however, various conflicts between fruiting plants and frugivorous birds, for example, fruit pulp production is costly for plants, but provides frugivores with energy (Sorensen 1984;Fukui 1996). Fruiting plants and frugivorous birds are also in conflict over seed retention time (SRT), which is defined here as: the time from ingesting a fruit to the time when its seed(s) are eliminated, corresponding to the time spent passing through the bird's digestive system.Several studies have suggested that seed dispersal distance is a function of SRT, however, small seeds tend to be dispersed further (Hoppes 1988;Murray et al. 1994), indicating a relationship between seed size and SRT. Small seeds tend to remain in the gut longer than large seeds. Furthermore, long SRT in the avian gut apparently enhances seed germination (Barnea et al. 1991). Seeds ingested by blackbirds Turdus merula usually had a higher germination rate than those ingested by bulbuls Pycnonotus xanthopygos. This differential rate in germination has been explained by longer SRT in blackbirds than in bulbuls. Longer SRT may increase abrasion of the seed coat by the avian digestive system and thus improve germination rate. SRT represents part of the handling cost of food for birds. Ingested seeds also represent a cost to frugivorous birds because the seeds displace gut volume that could otherwise be filled with digestible fruit pulp. Furthermore, the seed mass in- Abstract Seed retention time (SRT) of 16 fruit species in the guts of the Browneared Bulbul (Hypsipetes amaurotis), a major fruit consumer in central Japan, was studied to examine the relationship between SRT and fruit characteristics, i.e. fruit size, seed size, seed weight, and water content. Caged bulbuls were videotaped after feeding on fruits, and the time of defecation of each seed was recorded. Most seeds were always defecated in fecal pellets, with the exception of Aucuba japonica (the largest of the seeds studied), a seed of which was regurgitated on one occasion. Bulbuls defecate large seeds more rapidly than small seeds. The SRT of the last defecated seed, mean SRT, and standard deviation of SRT were significantly negatively correlated with seed size, fruit size, and seed weight, while SRT of the first defecated seed and water content were not correlated with any of the fruit characteristics examined. This suggests that Brown-eared Bulbuls are somehow able selectively to eliminate bulky seeds from the gut rapidly in order to overcome digestive limitations. If birds would prefer fruit species with large seeds that they can regurgitate and with short seed retention times in the gut, the results suggest that large seeds have the advantage of quantity of seed dispersed. Small seeds retained in the gut for longer have the advantage of b...

Fruiting plants and frugivorous birds are known to interact. In endozoochory, frugivorous birds consume fruits and subsequently disperse seeds. It follows that fruit characteristics would have evolved to allow birds to consume fruits easily. However, one's benefit does not always mean the other's. There are several conflicts between fruiting plants and frugivorous birds in terms of nutrient content, retention time and number of seeds in a fecal pellet. Retention time of seeds in guts is particularly interesting. Longer retention time benefits plants directly by increasing seed dispersal distance but may involve indirect costs through birds' preference by reducing their consumption. To understand the exact role of seed dispersers in the reproductive success of fruiting plants, we should pay more attention to the possible conflicts between fruiting plants and frugivorous birds.

. 2005. Temporal changes of avian communities in Japan during the late 20th century examined using the phi coefficient. Jpn. J. Ornithol. 54: 86-101.Abstract. Long-term changes in bird communities in Japan were examined by using a binary-data-based similarity index of community -the phi coefficient. Published long-term data (study periodՆ20 years) of avian communities during the breeding season from five locations in Japan (Hokkaido, Iwate, Nagano, Tochigi and Tokyo) were compiled and species presence/absence data were used for the analysis. The phi coefficient was calculated between the species composition in a given year and that of the initial community in the first year of the observation period; the extent of similarity between them was tested using the chi-square statistic. Results suggest that there was a decreasing trend in the similarity index in three out of the five locations (Iwate, Tochigi and Tokyo) and that remarkable changes in species composition have occurred since the late 1960s in Tokyo, and since the late 1970s in Iwate and Tochigi. Temporal changes in species composition resulted from: (1) the loss of summer visitors and resident species, and (2) the appearance of bird species not present in the initial community. We concluded that the phi coefficient is useful for examining long-term temporal changes in avian communities and that the coefficient is preferable over other binary-data-based similarity indices because it is amenable to hypothesis testing.