Kenichi Ozaki

LANDSCAPE ANALYSIS OF NORTHERN GOSHAWK BREEDING HOME RANGE IN NORTHERN JAPAN

Abstract Large raptors such as northern goshawks (Accipiter gentilis) frequently have been the focus of conservation efforts because of their large area requirements and habitat sensitivity. We examined landscape-scale habitat selection of breeding goshawks and created a habitat model of goshawk landscape use in an area (1,600 km2) that contained forested, agricultural, and urban landscapes in northern Japan. From a systematic nest survey and extensive radio telemetry, we delineated 36 male home ranges (18 of them were approximated with similar-sized plots around nests) and 44 similar-sized unoccupied plots over the study area. The proportions of forest cover in each home range varied widely (between 2 and 88%). Despite this variation, goshawk landscape use was estimated accurately (classification accuracy = 84%) with a stepwise logistic regression model; the probability of occupancy was positively associated with the proportion of forest interior (>200 m from the forest edge) and that of open land <200 m from the forest edge, but it was negatively associated with the proportion of water and the mode of the slope. In home ranges, the proportions of forest interior and open land <200 m from forest edge complemented each other with the change in forest cover in such a way that the sum of the 2 variables always occupied >30% of the home ranges. These results suggest that a preference for the 2 different habitats, both of which may have a high prey availability, enables goshawks to nest in landscapes with a wide variety of forest fragmentation. The adverse effect of water on goshawk occupancy was due to the tendency of goshawks not to include a large river (>800 m wide) in their home ranges. This suggests that goshawks need connectivity between forest patches in their home ranges. The proportion of urban land was 19% lower in home ranges than in unoccupied plots. These results indicate that management efforts should focus on maintaining landscapes with high prey availability and connectivity between forest patches and on preventing urbanization over entire home ranges.

Ant predation suppresses populations of the scale insect Aulacaspis marina in natural mangrove forests.

MANY SCALE INSECTS ARE TENDED BY ANTS that consume their exudates as an important source of nutrition. Attendant ants, in turn, increase the survival and thus the population of scale insects by: (1) directly protecting them from predators and parasites; (2) removing honeydew to prevent mold infestation; (3) transporting the scale nymphs to suitable feeding sites on host plants; and (4) building shelters to protect scale insects (review in Way 1963; Buckley 1987). These benefits are so strong that after removal of the ants, scale insect populations often decrease rapidly and are eliminated (Way 1954, Hanks & Sadof 1990, Itioka & Inoue 1996a). Sometimes scale insects are killed by tending ants; but even so, the density of scale insects with ants is much higher than without ants, indicating a net positive effect of ant attendance (Strickland 1951, Way 1954). Ants also benefit scale insects that do not produce exudates; DeBach et al. (1951) found that honeydew-feeding ants increased the populations of several armored scale insects (Diaspididae) that did not produce exudates, by depressing populations of their natural enemies. These findings all indicate that ants have positive effects on scale insect populations. In this study, however, we demonstrated a net negative effect of ants on scale insect populations: ants were found to prey on and suppress populations of the scale insect Aulacaspis marina Takagi and Williams (Homoptera: Diaspididae) in natural mangrove forests. Aulacaspis marina was abundant in plantations of the mangrove tree Rhizophora mucronata Lamk. (Ozaki et al. 1999), where its density reached .200 mature females/leaf. Feeding by scale insects at these densities caused the leaves to become discolored and drop early, which consequently killed the trees within five months. In contrast to its high population density in the plantations, however, A. marina was very scarce in natural mangrove forests adjacent to the plantations. To test the hypothesis that predators were responsible for the different scale insect densities in plantations and natural forests, we introduced R. mucronata seedlings infested with the scale insects into both types of forest, and compared the survival of the scale insects. Then, their survivals on seedlings exposed to and protected from ants were compared to assess the magnitude of ant predation in natural mangrove forests. The experiments were conducted at the Prapat Benoa National Forest, Bali island, Indonesia (88459S, 1158159E) in 1998. Since 1993, 150 ha of abandoned shrimp ponds have been reforested, mainly with R. mucronata. A large number of planted saplings have been heavily infested and killed by A. marina in this area. This scale insect, however, rarely has been observed in the adjacent 340-ha natural mangrove forests that remain along the outside margins of the plantation area, although one of the dominant species (Rhizophora apiculata BL.) in the natural forests is as susceptible to A. marina as R. mucronata (Ozaki et al. 1999). To compare the effect of natural enemies between the plantations and the natural forests, we examined

Maternal care in the red-headed spruce web-spinning sawfly, Cephalcia isshikii (Hymenoptera: Pamphiliidae)

We describe oviposition and maternal behavior in the sawfly Cephalcia isshikiiand examine the adaptive significance of this behavior. Females deposited eggs in a single but loose cluster on needles of terminal twigs of spruces, Piceaspp., and remained with the eggs usually on the underside of the twig facing toward the tip. The female attended her eggs until death without taking food but did not follow the first-instar larvae that moved from natal needles even if she survived until then. When the female was disturbed, she usually moved toward the source and attempted to bite it. Though at much lower frequencies, this aggressive behavior was also observed in gravid females and even in males. Field observations and female removal experiments indicated that the female enhanced the survival of the eggs through the reduction of arthropod prédation.

Landscape versus local factors shaping butterfly communities in fragmented landscapes: Does host plant diversity matter?

Conversion of terrestrial land for the purposes of agriculture and urban development continues to result in loss and fragmentation of natural habitats. In this study, we focus on butterflies and investigate the relative importance of landscape-level habitat amount (the proportion of woodland area within a landscape), habitat fragmentation (length of woodland edges within a landscape), urbanization (the proportion of urban area within a landscape), and local host plant diversity for butterfly communities in a fragmented landscape in Hokkaido, northern Japan. Butterfly species observed in the field were grouped into woodland and open-land species. The results showed that both landscape and local factors shape the butterfly community. At a landscape-scale, woodland butterflies positively responded to woodland area and negatively to edge density, whereas open-land butterflies showed opposite responses. At a local-scale, positive influences of local host plant diversity on woodland butterflies were evident, but not for open-land species. These results suggest that negative influences of anthropogenic land-use changes on biodiversity could be mitigated by strategies aimed at stopping the spread of woodland edges and providing a wide variety of different host plant species in the landscape. Unfortunately, this study implies that further increases in habitat loss and fragmentation and decline in host plant diversity lead to a homogenization of local biological communities and functions.

Density effects on the conifer mortality in declining spruce-fir forest in northern Japan: Implication of bark beetle attack to, cause spruce decline

We examined mortality patterns of two conifer species in relation to tree abundance and species composition in a declining spruce-fir forest in Akan National park, Hokkaido, northern Japan. The data taken from eleven 58 m × 58 m square study plots showed that percentage basal area (BA) of dead trees of canopy trees during the last decade was 49% forPicea jezoensis (Sieb. et Zucc.) Carr and 30% forAbies sachalinensis (Fr. Schm.) Masters. InP. jezoensis, percentage basal area (BA) of dead trees was positively related to both BA of its own species and proportion of it to BA of all species, whereas it was not significantly related to both of these variables inA. sachalinensis. Multiple logistic regression with dbh as a confounding factor also indicated that, inP. jezoensis, the proportion of dead stems was positively affected by the stem density of conspecific trees, whereas it was negatively affected by the stem density of the other species in each study plot. However, inA. sachalinensis, the proportion of dead stems was significantly related to neither of these factors. The different mortality pattern between two conifer species suggests that the spruce bark beetle,Ips typographus (L.), which is a serious pest of spruce, may have caused theP. jezoensis decline. Instead of wind-throw or thinning that usually initiate this bark beetle attack, some unknown factors seemed to predispose the trees to insect attack. These unknown factors may also explain the high mortality ofA. sachalinensis in this forest.