1) The present paper dealt with the problems of line transects in animal ecology. Several methods of the use of line transects were compared with one another and criticised both from the theoretical and practical point of view. 2) The densities of certain woodland bird populations were estimated by census and sample counts at the same time and in the same place. When the results were compared a serious discrepancy was observed between the density determined by complete census and the density determined by sample counts and mathematical calculation. 3) It was concluded that the discrepancy was probably due to the variability of conspicuousness of the birds. The influence of conspicuousness of the animals on the results obtained by sample counts was discussed under the assumption that conspicuousness may vary not only with the species, with the observer, with the habitat, and with the distance, but also with the speed of the animals. 4) The methods of line transects were classified from a practical stand point according to what kinds of animals are to be sampled. The precautions to be taken in the application of each method was also suggested.
Observations on the roosting behaviour and the change of roost during and after breeding are reported. In conclusion, the factors for selecting roost are as follows: 1) Safety and the environment, 2) Presence of both roosting and gathering places, 3) Kind of plants, 4) Size of roost, 5) Correlation with flock size. Although there existed many bamboo thickets, those selected for roosts were always adjacent to the rice paddies which made them less easily approached by man. The kind of roost was, beside bamboo thicket, reed beds of river side, desiduous trees as well as pine trees. These roosts were not necessarily selected seasonally, though in winter bamboo thickets were always used. It also seems that they determine the roost size by their flock size, thus in August, a flock of about 400 birds used the extensive bamboo thicket (as in winter) in 1955, but less than 100 birds roosted in the pine trees nearby, in July, 1956 and August, 1954. The factors for change of roost may be as follows: 1) Environmental factors (a. Change of feeding grounds, b. Movement of the flock due to a), 2) Natural or human factors, 3) "Special attraction, " 4) Overpopulation ("flooding effect"), 5) Following effect and mono-flock preference (psychological). It was observed that until the rice plant around the winter roost is cut rather extensively, this roost had no value other than a part of the feeding ground, because a flock feeding at a fruit tree within that roost flew off in the evening to other roost used in this season (summer). When the rice plant at the feeding ground of the breeding area become fully grown, the flock moved north to the vegetable fields and changed the roost. This change of feeding ground and roosting place seems to be directly correlated, rather than secondarily determined by the distance of old and new roosts from the new feeding ground. A suggestive case was encountered in which a typhoon might have caused the change of roost, and human persevierance should also become a cause. The attachment of next-boxes near the spring roost has apparently given a "special attraction" to the starlings, because this roost was maintained in the second year until summer, the season in which they used to abandon that roost in the previous years. This resulted the overpopulation at this roost and by "flooding effect" the flock was splitted into two, each thereafter roosting at two new roosts about 4km. apart. In this case, the original roost was perfectly abandoned showing their mono-flock preference. In splitting up the flock they gradually established new roosts by following the others and some confusion was observed, especially in young birds, in their behaviour of undecision (an usual behaviour in changing the roost). They start to a roost but soon circle back, or swing to the direction of the other roost or sometimes take a zigzag course between the two destinations, while the "back flight" from the roost where they have just arrived was often observed. An additional note on the feeding behaviour is given. In autumn, sparrows and starlings gather together at rice paddies, but eat different foods. Especially, the starlings search for rice worms from cut stems both remaining on the ground and hung from the poles.
The author took note on this intestinal lymphatic divertikel of birds, which is known as the remain of the duct of yolk sac of chick stage. The presence or absence of the divertikel in adults, the length, distance from gizzard and the position (ratio of this distance for total length of intestine) are given, and the histological observation on two samples, which shows the lymphatic nodules, is reported. As has been discussed by other authors, it remains as a general rule in the nidifugous and water or terrestrial birds and in those which has developed caeca, but with exceptions in each case. These rather many exceptions indicate that this divertikel, though in some cases it shows secondary development, is not considered very significant functionally and adaptively.
M. pectoralis major of birds in general consists of M. pect. m. proprius and lateralis (Kuroda, '60) and in soaring birds such as some hawks and the Tubinares a distinct deep-seated layer, M. pect. m. profundus (white muscle in the Tubinares) (Kuroda, 1. c.), is differentiated. The M. p. m. lateralis, generally ignored, is an important part in flight in pulling backward the wing (humerus) struck down by M. p. m. proprius, thus giving the propelling effect to the wing. Comparison of this part of the pectoral muscles in various groups of birds is shown in Plate 1. The comparative weight of M. p. m. profundus (Fig. 3, H, I, L, N) in some species of the Tubinares is listed; it is best developed in the albatross in which the M. p. minor (M. supracoracoideus) is the smallest. The relative weight of entire pectoral muscles to the body weight and that of small pectoral muscle to large pectoral are listed by Orders of birds. As a rule smaller species of a group of birds generally have more developed small pectoral relative to large pectoral. The former muscle is least developed in some hawks and the Tubinares which are soarers and best developed in the wing-diving sea-birds, the Alcidae. Their relative development is heighly adaptive to the way of flight. In the herons, an anterior superficial layer of the M. p. m. proprius can be distinguished, and this was named, the M. pect. major antero-superficialis.
The breeding success of Great Tit, Parus major, was investigated at Musashi Imperial Tomb Area in 1959. 80 nest-boxes were provided per 50 m-grid. The number of nests initiated were 26 and the nests at which the clutch completed were 10. The clutch sizes were somewhat larger in early than in late clutches, though not statistically significant. The nest from which the nestlings fledged was only one. This very low breeding success is remarkable.
The tibial muscles of an adult male ostrich which died at Ueno Zoo, Tokyo, 1959, was examined. Unfortunately, only the muscles of the right leg was available and they were already cut at the heel joint, and the time was not enough for detail examination. Of the 13 tibial muscles to be found in oridinal birds, nine (if M. perforatus et perforans digiti II and III (Fig. 1, E) are separated, ten) were present and are briefly described. The total muscle weight was 5.950gm, M. gastrocnemius and M. peroneus longus, especially the former, were extremely developed completely enveloping the hole proximal part of the tibia. Other muscles, mostly with tendon to toes and also M. tibialis anterior which lifts the tarsus, were only weakly developed. These conditions are adaptations for the use of heavy tarsus solely for running. But, the general muscular system, though simplified, was similar to that of ordinal avian type.