Japanese Journal of Ornithology Vol. 66(2017) No. 1

ARTICLES

The density of Eurasian Tree Sparrow Passer montanus nests in relation to proximity to urban parks and the presence of air vents in houses

Tsubasa SUTO, Kosuke KAKIZAKI, Satoshi AOYAMA, Osamu K. MIKAMI

Released: May 13, 2017

p.1-9

A decline in the numbers of common species results in the loss of ecosystem services. This is because common species are represented by large numbers of individuals that collectively inhabit wide ranges. The population of the Eurasian Tree Sparrow Passer montanus, once one of the most numerous birds in Japan, is in decline. Two explanations for the decline have been proposed. The first suggests that the holes and crevices used by sparrows for nesting in artificial structures have decreased as modern house construction methods leave few holes and crevices available to them. The second suggests that the loss of urban green areas, such as parks, has had a negative effect on the reproductive success of the sparrows. However, neither of these hypotheses has been fully investigated. In this research, we sought answers to the following questions: 1) Is the density of Eurasian Tree Sparrow nests in residential areas affected by proximity to urban parks? 2) Is the density of sparrow nests in residential areas related to the numbers of holes and crevices available in artificial structures? Twenty-four study areas (each 10,000 m²) were established in Hakodate City, Hokkaido, Japan. Half of these areas were adjacent to urban parks, and half were at least 200 m away from urban parks. We counted the number of nests and the numbers of holes and crevices in artificial structures in each area. After selecting a model using Akaike's information criterion values, the best model included the presence of urban parks adjacent to study sites and the number of air vents at each study site. The decline in the population of the Eurasian Tree Sparrow in Japan is expected to continue because of continuing urbanization and the combined losses of urban parks and holes and crevices in artificial structures.

What size and weight of Manchurian Walnuts Juglans mandshurica should crows consume?

Satoshi AOYAMA, Tsubasa SUTO, Kosuke KAKIZAKI, Osamu K. MIKAMI

Released: May 13, 2017

p.11-18

Carrion Crows Corvus corone drop Manchurian Walnuts Juglans mandshurica onto the ground in order to be able to break them open and eat their contents. Previous studies of avian prey-dropping behavior allow us to predict that the crows make a range of decisions when foraging in this way. They must first choose their walnuts then choose the drop site and the drop height, in order to raise the efficiency of their foraging behavior. To understand this decision making process, we must first understand the characteristics of walnuts. In this investigation we had four objectives: 1) to establish from what height walnuts must be dropped in order to break them. 2) to determine whether the weight of walnuts affects their likelihood of breaking when dropped from a certain height. 3) to understand the relationship between walnut size and weight and the weight of the edible contents. 4) To confirm whether crows really choose walnuts. Our results were as follows: 1) Nine out of thirty (30.0%) walnuts broke when dropped 10 times from a height of 12.7 m, whereas three (10.0%) broke when dropped from 8.8 m, and only one (3.3%) broke when dropped from 4.8 m. 2) The weight of the walnuts was independent of their breakability. 3) There were positive correlations between the above two sets of variables. 4) Crows preferentially chose heavier walnuts.

An efficient method for estimating Jungle Nightjar habitat distribution, considering the temporal variation of song frequency

Michio SAIKI, Susumu GOTO

Released: May 13, 2017

p.19-28

We investigated the temporal variation in the song frequency of the Jungle Nightjar Caprimulgus indicus, and categorized it in three ways, as: 1) peaks during the middle of the night, 2) peaks at dusk and dawn, and 3) lacks distinct peaks. In order to estimate song frequency, a sampling strategy of five or ten minutes investigation at hourly intervals was more effective than an intensive 50-min investigation during twilight. We suggest that sampling for five minutes, 10 times at hourly intervals is the most efficient method for estimating the habitat distribution of the Jungle Nightjar.

SHORT NOTES

Breeding behavior of the Japanese Leaf Warbler Phylloscopus xanthodryas

Takahito KANEKO, Gen MORIMOTO, Keisuke UEDA

Released: May 13, 2017

p.29-33

The Japanese Leaf Warbler Phylloscopus xanthodryas is a common summer visitor to high montane areas of Japan, yet basic information on its breeding behavior remains unclear. In this paper, we report that it breeds twice per breeding season (n = 2), and that there is variation in the sharing of food provisioning between the parents of 10-12 day old nestlings. Two nests were cared for only by females. Parental food provisioning showed great variation. These observations are based on individual identification by means of unique color rings and DNA sexing during five breeding seasons.

Water bathing and dust bathing by the Eurasian Tree Sparrow Passer montanus

Koji HONMA

Released: May 13, 2017

p.35-40

Eurasian Tree Sparrows Passer montanus were studied to identify their trends in the sequence of water bathing and dust bathing in an urban garden in Arakawa City, Tokyo. In cases where both forms of bathing were performed repeatedly, we found that bathing in water preceded dust bathing in 18 of 19 cases in 2014, and in 24 of 28 cases in 2015. During previous observations in Kanagawa Prefecture, water bathing preceded dust bathing in seven of nine cases. This tendency is inferred to be a measure of the sparrows choosing to dry themselves after bathing in water.