Avian egg size varies widely within populations and larger egg sizes reflect greater investment by the female parent. Whether, and how, the extent of egg size variation affects postnatal development, are important questions affecting our understanding of optimal resource allocation between pre- and post-hatching parental investment in altricial and semi-precocial species. Though much research has been carried out in the hope of answering these questions, the feeding ability of parents confounds the results. To verify a possible advantage of hatching from a large egg on chick growth, without the confounding effect of parental feeding ability, an artificial feeding experiment was carried out on the Rhinoceros Auklet Cerorhinca monocerata, a semi-precocial alcid species. Hatchlings from various sized eggs were reared with the same amount of food in separate cages. To verify the advantage of larger eggs, I tested whether the wing lengths of chicks from large eggs grew faster than those from smaller eggs; such growth is critical to chick survival at fledging. The hatchlings from large eggs were found to have greater mass, longer wings and better body condition than those from small eggs. The chicks from large eggs had greater growth only in their wings during the initial postnatal development. This accelerated growth resulted in them having longer wings at fledging. These results indicate that large egg size in the Rhinoceros Auklet provides a guarantee of chick growth and fledging success despite an unpredictable environment during the chick rearing period.
The breeding bird community of the Ogawa Forest Reserve (OFR), an old-growth deciduous forest in central Japan, was surveyed and compared with those of similar forests on Honshu, the largest island of Japan. Of the 63 bird species observed, 51 were potential breeders within the OFR, and 31 of these had territories in the 12-ha study plot for at least 1 year during the 5 study years. Annual changes in the breeding community were small; the average total density was 491 pairs per 100 ha and the average number of species was 25.6. The Great Tit Parus major was the dominant breeding species, followed by the Willow Tit P. montanus, Narcissus Flycatcher Ficedula narcissina, Coal Tit P. ater, Varied Tit P. varius, and Ashy Minivet Pericrocotus divaricatus, a national red-listed species. Some local red-listed species, such as the Brown Flycatcher Muscicapa dauurica and White-backed Woodpecker Dendrocopos leucotos were also common in the OFR. The results suggest that the OFR harbors a breeding bird community similar to its original status. Cluster and ordination analyses indicated that the avifauna of the OFR was characterized more by the elevation than by the geographic location and thus represents the original bird species diversity of the low-montane beech forests of Honshu. As low-montane areas of Japan have been degraded in recent decades, the OFR provides a valuable indicator of bird species biodiversity for sustainable forest management.
Morphological measurements of Okinawa Rail Gallirallus okinawae were made to evaluate methods of sex determination. Males were significantly larger (P<0.05) than females for 23 of the 25 features measured. Forward discriminant function analysis identified eight of the most useful measurements as maximum wing, exposed culmen, tarsus, total head, gape, bill height, body weight and third toe length. Further analysis selected total head (TH) and bill height (BH) as the most useful variables to determine sex and produced the discriminant function: 0.467×TH+0.827×BH−53.811, which correctly identified the sex of 100% of the individuals in the data set. Bill and iris color proved useful for determining age, as did the tip shape and color of the primary feathers. Characteristics of juvenile primaries were especially useful, since the birds retain their first year plumage until molting at about one year old. Individual variation also exists, however, requiring comprehensive evaluation of all biometrics and features for some individuals.
To confirm rates of mortality and to improve means of release of captive-bred Copper Pheasants Syrmaticus soemmerringii, 111 individuals were released into a natural refuge area in Tochigi Prefecture, central Japan, and radio-tracked. Survival of pheasants more than 13 months old was significantly longer than those less than 12 months old. There were significant differences in the number of days they survived depending on the season at which they were released. The longest survival was of individuals released in summer, followed by spring, then winter, and survival was shortest among those released in autumn. Depredation was the main cause of death of released pheasants: by mammals 45.3% and by raptors 22.7%. Death by hunting also occurred but outside the area where the pheasants were released (2.1%), and only one individual (1.0%) was judged to have died due to starvation or weakening. Raptor predation was remarkably high in areas with little or no undergrowth. These results suggest three important proposals regarding the release of pheasants: 1) the release should not be conducted in predator-abundant areas; 2) summer is the best season for release; 3) release in hunting areas or near the boundaries of hunting areas should be avoided.
Lesser White-fronted Goose Anser erythropus is recognized as a globally threatened species. Very small numbers stage and winter in Japan, mostly individually, as families or sometimes in small flocks. Since beginning to observe this species in 2001 at Sarobetsu, northern Hokkaido, Japan, we have noted increasing numbers. The increase, from a few individuals (2001–2004) to flocks (2005–2007), is of interest, given the threatened status of this species. Lesser White-fronted Goose now regularly migrates through Sarobetsu, giving us opportunities to observe this relatively rare winter visitor to Japan. In order to help clarify the status of this threatened species in Japan, we describe and discuss the change in numbers, the proportion of juveniles in flocks, family size and length of stay.
We investigated bird nest predation on Miyake Island where the Japanese Weasel Mustela itatsi has been introduced. From observations of Japanese Bush Warbler nests, we estimated survival rates of 0.498 and 0.848 in incubation and nestling stages, respectively. Artificial nests coupled to an automatic image recording system showed that weasels were bird nest predators on three occasions. No other potential predators visited the nests; before the weasel introduction, nest predation was rarely reported on the island. The incidence of predation on artificial nests increased as a function of the density of predated artificial nests in the neighborhood. Other nest-site characteristics were not related to nest predation, except for height above the ground. Lower nests had slightly higher risks of predation. Hence, the fate of a nest appears to depend on whether it is located within home ranges of the Japanese Weasel. Weasels may easily find nests located within their activity ranges irrespective of their site characteristics. Japanese Weasels must be regarded as a major threat to breeding birds on Miyake Island.
To examine the breeding system of the Ashy Cuckoo-shrike Coracina cinerea, a species endemic to Madagascar, we studied the contributions made by males and females of three pairs to incubating, brooding, and feeding the young. The study was conducted at Ranomafana National Park, southeastern Madagascar, from October to December in 2007. Both sexes participated in incubating and brooding. During the nestling period, both sexes delivered food (mainly caterpillars and grasshoppers) to the nestlings. The nestling period lasted about 24 days. No helpers were observed during our study. These results suggest that the Ashy Cuckoo-shrike is socially monogamous.
A breeding pair of Hodgson's Hawk-eagles Nisaetus nipalensis brought prey items of four vertebrate taxa with a mass range of 5–1900 g to the nest. In the late breeding period, when both sexes performed provisioning, the male delivered birds and lighter items, whereas the female brought reptiles and heavier items, resulting in significant sexual prey partitioning regarding both taxa and mass. In the nestling stage, coinciding with the late breeding period, the male achieved a provisioning rate similar to that of the female, despite hunting bird prey, whose agility reduces their vulnerability, indicating the male's greater overall foraging ability.
To determine the annual and seasonal patterns in the transport of seeds by Great Tits Parus major, we investigated the species and number of seeds in the feces of Great Tits deposited in roost boxes during the winters of 1992–99. At least 63 morphological types of seeds were considered to have been transported after they were eaten by the tits and excreted into the feces. Forty-nine of the 63 seed types were excreted only in one of the seven winters. These results suggest that Great Tits transported seeds of various plant species sporadically.
The numbers of the Greater White-fronted Geese Anser albifrons frontalis were monitored during winters from 2003/2004 to 2006/2007 throughout Japan. The annual average number of geese in Japan increased from 91,000 to 115,000 during these years and the maximum number reached was 138,000 in 2006/2007. Most geese (84%) stayed in northern Miyagi, and residual flocks were observed in other areas during winter. In the largest wintering area for this species in northern Miyagi, the number of geese has increased from 15,000 in 1987/1988 to 111,000 in 2006/2007.
The sole record of a bee-eater from Japan, a specimen in the collections of the AMNH, has been reexamined. The bird is confirmed as a female Rainbow Bee-eater Merops ornatus, the collection data written on the label in Japanese is translated and the measurements, plumage and molt of the bird are also described.