The distributional change of Skylarks Alauda arvensis in Tokyo, central Japan, was studied in the 1970s and 1990s. There was a precipitous decline in the number of sightings of Skylarks in Tokyo from 101 survey squares in the 1970s to 28 in the 1990s. Discriminant analysis revealed that the key factors affecting the occurrence of Skylarks were the area of fields, grasslands, and shores. In Tokyo the total area of fields significantly decreased from the 1970s to the 1990s, and the fields themselves became fragmented, but there were no significant changes in the area of grasslands and shores. The area of fields was the most important factor in the 1970s, but became the third most important factor in the 1990s while shores became most important factor. The percentage of fields under wheat, as preferred by skylarks, decreased between the 1970s and the 1990s, while the percentage of vegetable fields increased. The decline of Skylarks breeding in Tokyo seems to have been caused primarily by the decline of the area of fields and by change in the type of crops.

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The influence of varied nest box installation densities on the usage rate by Tree Sparrow Passer montanus and tit species Parus spp. was investigated at a golf course in Nagatake, central Japan. Increasing nest box densities negatively affected nesting by Tree Sparrows, but positively affected that by tit species. The effect of environmental temperature was also analyzed, and increased temperatures were shown to correlate with increased nesting by Tree Sparrows, but had no relationship to tit nesting. These results suggest that the population of Tree Sparrows may be restricted by food resources, rather than by a limited availability of nest sites. As a result, if the number of nest boxes are increased, Tree Sparrows may not increase nesting rates, and more nest boxes would be available for use by tit species. Increasing the installation density of nest boxes may be an effective method for enhancing the population of tit species. The mechanism causing the number of Tree Sparrow nests to decrease when nest box densities were increased is unknown, and requires further study.

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From December 2004 to early April in 2005, the effects of vegetated artificial islands on the habitat use of hunting Eastern Marsh Harriers Circus spilonotos, were studied at Yanaka Reservoir (ca. 450 ha), in Watarase Marsh, central Japan. The observations were conducted in four 500 × 500 m quadrats, one of which contained six artificial islands (0.1-0.32 ha). Islands were vegetated primarily with reeds (Phragmites spp.) of approximately 2.5 m in height. Another quadrat contained open water without artificial islands, and the remaining 2 quadrats contained dense reedbeds, which is an essential hunting habitat for harriers. The hunting flight frequency of the harriers in the quadrat with artificial islands was significantly higher than that with only open water. In the quadrat with artificial islands, the hunting flights per 100 × 100 m grid cells were recorded, and cells with islands had a significantly greater number of hunting flights than that of grid cells without islands. On the other hand, there was no significant difference in the hunting flight frequency between the quadrat with artificial islands and quadrats covered with reedbed. The harriers were observed to make a total of 17 hunting attempts. Of these, 76.5% occurred on the periphery of the islands, 17.6% toward the center of the islands, and 5.9% over the surface of the reservoir. These results suggest that vegetated artificial islands enhance the hunting activities of Eastern Marsh Harriers.

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The distributions and habitats of the three species of wagtails, Japanese Wagtails Motacilla grandis, White Wagtails M. alba and Gray Wagtails M . cinerea were studied from April to July in 2004 in Utsunomiya City, central Japan, in order to reveal changes after 20 years. The species, number and breeding status of the wagtails were recorded in 500m quadrate units, each of which was classified as one of six types of habitats: city, residential, agricultural, river, industrial and hilly areas. The city and residential areas have expanded, whereas agricultural and hilly areas have decreased in the study area. Although the breeding distribution and habitats of M. grandis never changed, those of M alba and M. cinerea have changed significantly. M. alba have expanded their distribution into agricultural and river areas where they did not occur 20 years before. Coexistence of the two species may be enabled by lowered competition for nesting sites in the agricultural and river areas due to urbanization. On the other hand, M. cinerea, retaining their habitat preference, have lost a large number of quadrates in distribution. The factors affecting this change are not clarified.

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Baikal Teal Anas formosa is a species of dabbling duck, distributed from far eastern Siberia to eastern Asia. It is a rare species, identified as a vulnerable by the IUCN. We examined the food preference of Baikal Teal by laboratory experiments. In the experimental cages, male and female Baikal Teal were kept separately and five types of grain (rice, soybean, wheat, millet and corn) were provided to them. The consumption rate was compared among foods. First, when the foods were given separately, wheat and millet were more frequently consumed. Secondly, when the five types of food were mixed and provided, millet was more frequently consumed. The results suggested that Baikal Teal preferred smaller sized grains than larger ones, such as soybean and corn

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The change of nest construction and shape in tit Parus spp. and Tree Sparrow Passer montanus were studied at about 3,000 nest boxes placed at golf courses in Japan. Since 1996, the recorded thickness of tit nest cups, and thickness and shape of Tree Sparrow nests have changed. The ratio of thin-walled tit nests has been increasing over the period from 1996 to 2000. The ratio of unusually open shaped tree sparrow nests rapidly increased in 1998 and 1999, and slightly decreased in 2000 and 2001.
The timing of these nest shape changes coincided with the increased nest box destruction by crows Corvus spp. (also reported by the author in this volume). The change in nest shape may have been a result of les effort spent on nest construction, in an attempt to avoid crow predation.

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Crow species Corvus macrorynchus, C. corone in Japan have been known to physically damage nest boxes installed for passerines, essentially destroying the boxes so that they are unusable by the intended species. The frequency of nest box destruction by crows suddenly increased throughout the Japan in 1995. The activities reached their peak in 1996, and have decreased by half since 1997. In 2000, nest box destruction by crows had almost ceased. It is not known why the nest box destruction suddenly began and ended over the course of 5 years.

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I searched for carcasses of Jungle Crows Corvus macrorhynchos at Rikugien Park, located in the center of Tokyo, for 1 year in 2002. A total of 44 dead crows were found. The seasonal variation in occurrence of the carcasses shows that 68% of them were found in spring: March and April. March-April is the beginning of the breeding season for crows, and breeding pairs claim their territories. The young non-breeding birds may be driven away from the territories and die from lack of food, because the territories usually cover resource-rich sites, such as those with household waste. Consequently, the mortality rate of young crows increases in spring. During my research the number of roosting Jungle Crows of Rikugien Park was about 600 to 2,000, and the mortality rate of Jungle Crows is estimated at more than 2.5 to 8.3%.

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