1. Current breeding status of the endangered Short-tailed Albatross Dimedea albatrus, was reported based on two visits a year, i. e. egg and chick seasons, to Torishima, the southern Izu Shoto, on which the only known breeding station for this species exists. 2. In the 1977/78 season, 73 adults were observed at the beginning of the season, and at least 12 chicks, but not larger than 20, seemed to be reared. In 1978/79, 80 adults at the beginning, 95 in the chick season, were observed and 22 chicks were reared. 3. Although recent counts of adults indicate steady albeit very slow increase in numbers and perhaps 50-60 pairs are actually breeding currently, the production of young has been smaller than expected. 4. Comparative breeding data in the early 1960's and of recent seasons suggest that the nesting success is low recently, particularly at the east part of the breeding colony, where vegetation has become stunted in the last two decades. It was suggested that this change in vegetation might be a factor contributing to observed low breeding output. 5. In March 1979, an expedition party rediscovered 16 Short-tailed Albatrosses on Minamikojima in the Senkaku Retto, the southwestern Ryukyus, although breeding was not confirmed. From these observations the total world population was roughly estimated to amount to well over 150 and perhaps in short reach of 200. 6. Protection measures effective at the breeding ground were proposed and the status of the Black-footed Albatross nesting on Torishima was also reported in brief.
1. A study on the feeding ecology of the nestling Great Tit was carried out in the evergreen broadleaved forest from 1975 to 1979. The food consumption, excreting rate, body weight increment and maintenance cost were measured in the dry matter weight and calorific content. 2. A nestling consumed 0.5g. dr. of food per day at the second day and attained at the maximum value, 1.3g. dr., at the tenth day. The mean food consumption of a nestling more than ten days old was 5.56g. fr. or 38% of the body weight. Total amount of food consumed for fifteen days from hatching to fledging was 65.65g. fr. per nestling. The food consumption was not correlated with the brood size. The amount of feces excreted per nestling per day was 2.0, 5.6 and 8.2g. dr. at the fourth, eighth and fourteenth days, respectively. The assimilation rate varied between 26% and 57% of the ingested dry matter. The growth rate attained to the maximum value, 0.34g. dr./day, at the fifth day. The maximum maintenance cost was 0.5g. dr. 3. The food consumption was 3.7, 6.0 and 7.0 Kcal at the fourth, eighth and fourteenth days, respectively. The excreting rate was 0.7, 1.7 and 2.8 Kcal at the fourth, eight and fourteenth days, respectively. The assimilation rate varied between 52% and 72% of the ingested energy. The maximum maintenance cost was 4.4 Kcal. 4. Each of the food consumption, excreting rate and maintenance cost was greater in the present study than the respective values obtained in the larch wood by Royama (1966). The high ambient temperature in the ever-green broadleaved forest seems to be concerned with these differences.
1. The census effectitvities of every species which inhabits more than two study areas are shown in Table 1. The vegetation profile of each study area is illustrated as in Fig. 1. 2. The differences of the census effectivity of every species in Table 1 are almost not significant between study areas. But, when the census effectivities of all species inhabiting some two areas are compared disregarding the confidence limits, there is general trend such as the census effectivities of all species are higher in one of the two study areas excluding a few species. This trend is considered to be caused mainly by the change of the visual and auditorial range for observer reflecting every vegetation feature. The difference of the census effectivity between study areas will become more clear when more samples are collected. 3. The census effectivities of Erithacus cyane and Cettia diphone did not show a certain trend between two areas, because they are almost recorded by extraordinary loud songs in census. The census effectivity of Lanius bucephalus at Takizawa shows a adverse trend compared with that of the other species which inhabit the same area. This phenomenon was caused by exceptional case in Takizawa, where the linecensus route penetrates accidentally the center of every home range of Lanius bncephalus. 4. The relative differences of the census effectivities between every two study areas are calculated (Table 2), disregarding the confidence limits and excluding three species mentioned above. And finally, these relative values are standardized as shown in the bottom column of Table 2, In conclusion, the difference of vegetation feature as shown in Fig. 1 would give rise to about +38.4--27.9 relative % difference of the census effectivity. It was considered that the difference grade are derived from combination effects of tree height and tree density of stand.
1. The differences of the census effectivity between bird species, vegetation features and observers respectively are not dissolved by employment of average recording distance of each species as the observing radius (Fig. 1, 2, 3 and Table 1). 2. Then, it was considered that it is desirable to take a common distance (not far than 50m) for all species at the linecensus. 3. The relative values of the census effectivity in a 25m observing radius were calculated standardizing as 100% at a 50m (Table 2). The differences of the census effectivity between species, vegetation features and observers respectively can not be reduced in the case of 25m radius compared with that of 50m (Table 2, 3, 4). 4. The author recommends 50m as an observing radius in the linecensus compared with the other radius as a 25m, because it can get many sample counts and stabilize the results than another radius, and can eliminate the forest margine effect of road side.
1. This report dealt only with changes in specific census effectivity during the breeding season from the middle of May to early July. 2. The seasonal changes of the census effectivity were calculated for 18 species in Takizawa area based on 9 years census data (Fig. 1, 2). In them, only four species, namely, Turdus chrysolaus, Hypsipetes amaurotis, Streptopelila orientalis and Aegithalos caudatus, showed significant changes of effectivity during the breeding season mentioned above. But, the changes of Streptopelia orientalis and Aegithalos caudatus were considered to be caused by the chage of their densities. 3. Finally, in 29 species surveyed until now in Japan, it was considered that only three species, namely, Turdus chrysolaus, Hypsipetes amaurotis and Certhia familiaris, showed a definite seasonal change of the census effectivity. 4. As the cause of stability of the census effectivity during the breeding season in almost of the species concerned, it was supposed that registration chances of birds do not change during the breeding season because various bird activities such as song, call and flight show compensatory changes in the course of the season. 5. To minimize an error of density estimation derived from seasonal change of the census effectivity, samples should be collected from broad areas and covering a long period during the breeding season.
1. A density of birds is calculated simply as follows in my method; Ni=Zi/Ei (1) where, Ni is territory numbers of i species in an area censused, Zi is individual numbers recorded in census, Ei is the census effectivity of i species which derived empirically from the study area survey (Ei=Zi/Ni). Then, if there is a correlation originally between Ei and density itself, the equation (1) will become complicated. This paper dealt with this problem based on 9 years data taken at Takizawa and others. 2. The correlation coefficient (r) between the census effectivity and territory density in 9 years data of Takizawa area showed no significant level for every species (Table 1). Likely, the correlation coefficient between the census effectivity and territory density of several study areas, and between the song effectivity and territory density in Takizawa showed no significant levels (Table 2 and 3). 3. By these results, my simple method can be considered to be useful for the bird density estimation.
Investigations on the breeding biology of Dendrocoprs major japonicus and D. minor were carried out in Obihiro city, eastern Hokkaido, from late January to early July, 1976, and from late April to early July, 1977 to 1979. The main study area having an area of 16 hectares is a deciduous forest dominated by Quercus dentata and Larix leptolepis plantations at the campusof the Obihiro Agricultural High School located in the southern part of Obihiro. In additionto this area, nests of two species were observed in other area in Obihiro to obtain information about nests. During the study period 3 to 7 pairs of D. major and a pair of D. minor were found to breed in the main study area. At the beginning of the breeding period agonistic behaviour such as fights and chases were observed frequently in D. major. No overt agonistic behaviour, however, was observed between D. major and D. minor. D. major began to drum from early March and to nest from late April to mid-May, the nest excavation period being 27 to 30 days. Copulations were observed during the nest excavation period. Tree species in which D. major nested were mainly Quercus dentata in the main study area, and Larix leptolepis, Alnus japonica and so on in other areas. In a few cases they used gate pole or road-side trees as nesting site. They excavated nest in trunk of live trees except for 2 cases, e. g. a gate pole and a dead Quercus dentata. Diameter at breast height of nesting trees ranged between 20 and 65cm. Nest height from the ground ranged from 0.7 to 7m, with an average of 3.03m. The incubation period including egg-laying period was 15 to 20 days from mid-May to early June. Total incubation time in the daytime for females was longer than that for males, although both sexes incubated eggs. The incubation constancy described by Skutch (1962) increased gradually as the incubation period continued. Both sexes fed their nestlings for about 20 days from mid-May to early June. The times of feeding per hour increased till 14th day after hatching, and then declined. Young fledged in late June. It took 2 to 3 days for all young to leave the nest. The number of fledged young, which were fed by parents for a week after leaving the nest, were 2 to 4. D. minor excavated nests in trunks of dead trees or dead portions of live trees. The incubation period was from early June to mid-June, and the feeding period from mid-June to early July. It took 2 days for all young to leave the nest. Both sexes excavated the nests and incubated the eggs, but only the male fed nestlings in the nest observed.
1. In order to clarify the process of asynchronous hatching in the Little Egret Egretta garzetta, observations in a large heronry were made from 13 April to 19 July, 1977 in Mie Prefecture. Of 47 observed nests, 12 were investigated in detail by all-day observations for a total of 48 days. 2. The breeding cycle was divided into five breeding stages; stage 1 (nesting period), stage 2 (laying period), stage 3 (incubating period), stage 4 (nestling period inside nest) and stage 5 (nestling period outside nest). 3. Time interval of egg laying was a mean of 37.13 hours (about 1.5 days), the mean clutch size being 4.86 (range, 4-7). 4. Incubation began with the laying of the first egg and was shared equally by both sexes. Incubation rate (the percentage of the incubating hours in all observation hours) increased abruptly, and reached more than 80% (full incubation) after the laying of the second or third egg. Incubation period (days between laying and hatching of the last egg) was a mean of 23.44 days. 5. Time interval of hatching was prolonged with the order of egg-laying and was close to the mean interval of egg-laying (about 1.5 days) in the later eggs. The short interval of hatching between the 1st and the 2nd eggs was caused by the delayed hatching of the former egg. This delay will be interpreted as the delayed development of the embryo due to incomplete incubation.