Satoshi Yamagishi

Extreme endemic radiation of the Malagasy vangas (Aves: Passeriformes).

Abstract. Phylogenetic relationships of the family Vangidae and representatives of several other passeriform families were inferred from 882 base positions of mitochondrial DNA sequences of 12S and 16S rRNA genes. Results indicated the monophyly of the Vangidae, which includes the genus Tylas, hitherto often placed in the family Pycnonotidae. Our results also revealed the Malagasy endemic Newtonia, a genus never previously assigned to the Vangidae, to be a member of this family. These results suggest the occurrence of an extensive in situ radiation of this family within Madagascar, and that the extant high diversity of this family is not the result of multiple colonizations from outside. The extremely high morphological and ecological diversification of the family seems to have been enhanced through the use and ultimate occupancy of vacant niches in this island.

The effect of human disturbance and flock composition on the flight distances of waterfowl species

Abstract Flocking bird species tolerate an approaching human up to a certain distance. We measured this distance, i.e., flight distance, to an approaching small boat for 11 waterfowl species. The flight distances correlated positively with flock size and species diversity (Shannon index H′) in species that showed relatively short flight distances when they were in a single-species flock. However, we did not observe such a correlation for single-species flocks that showed relatively long flight distances. Only pochards (Aythya ferina), a species with large individual variation in flight distances, showed a positive correlation between flight distance and flock size in both single- and multispecies flocks. Flight distance seemed to be affected by usage of the water area: flight distances tended to be longer for waterfowl species that use a water area for foraging than for those that use it primarily for resting. Thus, the behavior of actively foraging species may be more affected by human disturbances than that of resting species.

Consequence of Inter Class Competition and Predation on the Adaptive Radiation of Lizards and Birds in the Dry Forest of Western Madagascar

Abstract n Species interactions among phylogenetically distant but ecologically related vertebrates were studied in a dry forest of western Madagascar to evaluate whether competition and predation between lizards and birds have reciprocally affected adaptive radiation in Madagascar. Of 49 terrestrial and diurnal birds regularly seen in the study forest, we identified six guilds as carnivore (5 spp.), omnivore (2 spp.), carnivore/insectivore (7 spp.), strict insectivore (15 spp.), insectivore/nectarivore (6 spp.), and frugivore (5 spp.). Twelve lizards species were classified as omnivore (1 sp.), strict insectivore (9 spp.), and insectivore with occasional frugivory and nectarivory (2 spp.). The most dominant guilds of the vertebrates in terms of biomass were folivorous/frugivorous parrots, doves, and lemurs (6.7 kg/ha), followed by insectivorous lizards (1.7 kg/ha) and insectivorous birds (0.8 kg/ha) in the Ampijoroa dry forest. Despite their lower biomass, insectivorous birds appeared to be competitively more advantageous than the lizards in terms of prey consumption speed (230 prey/ha/hr by birds vs. 35 prey/ha/hr by lizards). Insectivorous and carnivorous birds may have kept insectivorous lizards from radiating in various niches in Madagascar, and may have promoted a reclusive lifestyle in lizards.

Individual Differences in the Helping Behaviors of Cooperatively Breeding Rufous Vangas

Abstract The Rufous Vanga breeds cooperatively, with pairs accompanied by one or more helper males. Although the contribution of helpers may be considerable, helping does not enhance reproductive success. In this study, we investigated individual differences in helping behavior and discuss the adaptive significance of helping. Contributions by helpers were very low during the nest building and incubation stages, but were greater during the nestling stage. In the first half of the nestling stage, both one-year-old and older helpers contributed less than breeders, with one-year-old helpers feeding nestlings less frequently than older helpers. However, the contribution of helpers increased during the second half of the nestling stage, while that of breeding females decreased. Both provisioning frequency and the size of food items carried by one-year-old helpers reached the same level of older helpers during the second half of the nestling stage. One-year-old sons of breeding females contributed more than unrelated helpers, however relatedness did not influence significantly the contribution of older helpers. Contribution to provisioning by one-year-old helpers did not influence their fate in subsequent years. Our data did not reveal any direct fitness benefits gained by helping at the nest for one-year-old helpers, but suggested that they helped their mothers in order to gain indirect fitness benefits through lightening their mothers labor. Older helpers may have gained direct fitness benefits through advertising to an unrelated breeding female or by feeding their extra-pair fertilized off-spring.