Food and Food Consumption of Nestling Tits, Parus Major Minor and Parus Varius Varius, in the Ever-Green Broad Leaved Forests in Northern Kyushu
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昭和54年(1979)1月 Food and food consumption of nestling tits 1 Food and food consumption of nestling tits, Parus major minor and Parus varius varius, in the ever-green broad leaved forests in northern Kyushu Kazuhiro Eguchi* Introduction This paper is concerned with the food consumption of nestling tits, Great Tit (Parus major minor) and Varied Tit (Parus varius varius), in the ever-green broad leaved forests. Measuring the food consumption of the nestling may provide an important cue to elucidate the range utilization of adult birds, but there have hitherto been few studies on this problem. In the case of song birds in the forest, methodological difficulties have prevented the study on feeding ecology in advance. Of song birds, Paridae often use artificial nest boxes for breeding. Taking advantage of this habit, food or food consumption of the nestling of Paridae, particularly great tit, has been assessed in various habitats by means of the direct observation or automatic photography (Betts, 1955, Tinbergen, 1960, Gibb & Betts, 1963, Royama, 1966). On the other hand, it is well-known that species belonging to Paridae coexist in a same forest segregating their foraging site vertically in trees (Hartley, 1953, Gibb, 1954, 1960, Nakamura, 1970, Ogasawara, 1970, 1974). Great tit and varied tit, having similar pheno- types and similar breeding habits to each other, also coexist in the ever-green broad leaved forests. The former widely distributing in palaearctic subregion has been studied well, but the latter is not sufficiently explored yet (see Higuchi, 1975, 1976), because of its narrow distribution (Formosa, Southern Korea and Japanese Islands (Ornith. Soc. Jap., 1974)). Thus, interspecific relationship between these two species in the ever-green broad leaved forests is not obvious at all. Data obtained in the present study provide new informations on the food consumptions of great tit and varied tit in the ever-green broad leaved forests. Comparisons between different habitats and between two tit spcies were attempted, and then the author discussed on two points, characteristics of the ever-green broad leaved forests as the habitat of Paridae and possible segregation between two tit species. I would like to thank Prof. Y. Ono, Department of Biology, Faculty of Science, Kyushu University, for his invaluable suggestions and laborious correction of this typescript. * Laboratory of Ecology , Department of Biology, Faculty of Science, Kyushu University, 33 Fukuoka, Japan. (1) 2 山 階 鳥 研 報 第11巻 第1号(No.54) I also very grateful to Prof. H. Kubo, Faculty of Liberal Arts, Saga University, for his continued support and encouragement, to Dr. T. Iwamoto, Faculty of Education, Miyazaki University, for helpful comments on this typescript and to the members of Laboratory of Ecology, Department of Biology, Faculty of Science, Kyushu University for field assistance. I wish to thank Mr. Y. Tsukiji, Higashisefuri Village, Saga Prefecture, who gave me accomodation to research in Mt. Gongenyama. Study area Two areas were selected for the investigation, Mt. Gongenyama, Kanzaki, Saga Pre- fecture, and Mt. Tachibanayama, Fukuoka, Fukuoka Prefecture. Mt. Gongenyama, 455 m above sea level, is occupied by cedar woods, bamboo forests and the ever-green broad leaved forests. Study area lies in the ever-green broad leaved forests of which altitude ranged from 250 m to 400 m, consisting of Shiia Sieboldii and Cinnamomum Camphora in the tree layer, and of Aucuba japonica, Eurya japonica, Neolitsea sericea and Quercus glauca in the shrub layer. The investigation was started in 1975 using nine nest boxes, especially deviced for automatically photographing, set up by Prof. H. Kubo, Saga University, in 1974. This kind of nest box was put on the post about 1.5 m in height and was fitted with a camera at the back wall. In 1976, additional ten nest boxes for photographing were set up by the author. Besides these nest boxes, there were about 120 nest boxes of ordinary type in the study area. The investigation was carried out from 1975 to 1977. Mt. Tachibanayama, 368 m above sea level, is situated near by the Hakata bay and is occupied by cedar woods and the ever-green broad leaved forests. The investigation was carried out in the ever-green broad leaved forests from 180 m to 250 m above sea level, consisting of Cinnamomum Camphora and Machilus Thunbergii in the tree layer and Aucuba japonica, Eurya japonica, Neolitsea sericea, Quercus glauca and Damaacanthus indicus in the shrub layer. Fourteen nest boxes for photographing were set up in 1977. Method Each food item brought to the nest was photographed with the 16 mm movie camera, 8 mm movie camera or 35 mm motor-driven camera attached at the back of the nest box. The camera was wired to the micro-switch attached at the entrance hole of the nest box. The micro-switch had a lever horizontally extending across the hole, on which a bird perched and pushed down to get into or out of the nest. A digital counter was used or direct observation was made to record the frequency of visits to the nest by parent birds for the nest box to which the camera could not be equipped. At the nest fitted with the camera, direct observation was made in order to examine the efficiency of switching. The kind and the size of food items were determined by inspecting the film with the editor-viewer or microscopic projector. (2) 昭和54年(1979)1月 Food and food consumption of nestling tits 3 The weight of the prey brought was estimated as follows. 1) Caterpillar, moth, spider, etc. were collected in the habitat by sweeping(500-strokes per sampling time). 2)After anesthetized, the body length and body diameter of specimens were measured (for spiders, the length and maximum width of the abdomen were measured). Thereafter, each specimen was dried in the oven at 65℃ for 3 to 4 days and weighed. 3)Aregression linewas drawn,plotting the body weight(logarithmicvalue)against thebody diameter(logarithmicvalue)(see Appendix). 4) The body weight(dryweight)of each preybrought by the parentbirds was esti- mated from the value of body dimensionsmeasured on the photograph. Total amount of food brought to the nestlingper day was calculatedfrom the mean weight of food items, the percentageof differentfoods and totalnumber of visitswith foods per day. Result At both Mt. Gongenyama and Mt. Tachibanayama, great tit has only one brood and a short breeding season. The earliest date of first egg was March, 22 and the latest date was May, 24 from 1975 to 1977 (of twenty one nests). Most broods successfully fledging were in the nests from mid-April to mid-May. Broods hatching after mid-May seldom fledged successfully owing to stopping of supply of food by parents and heavy predation by the snake, particularly Elaphe conspisillata, and the weasel, Mustela sibirica itatsi. Although data on breeding are insufficient, varied tit also has only one brood and a short breeding season in both areas. The frequency of the visits to the nest by parent birds Great Tit Feeding frequency was measured at the nests of SU-3, KU-6 and NO-9 with the digital counters and automatic cameras, and U-3 by the direct observation. All nests ex- cept for NO-9, which is in Mt. Tachibanayama, are in Mt. Gongenyama. Fig. 1 and Tab. 1 show the daily change of the number of visits to the nest by parent birds. In both KU-6 and SU-3 (brood size was nine and ten, respectively), the number of visits was stable at about 13 times/nestling/day except that it was relatively high (about 21 times/ nestling/day) in the middle phase of the nestling period. Differently, visits to U-3 (four nestlings) increased gradually during the nestling period. Broods of both SU-3 and KU-6 suffered from the predation by snakes and reduced to half and two-third, respectively. Responses of parents to reduction of nestlings were different to each other. SU-3 suffered from the predation and nestlings were reduced from ten to five in the afternnon of 9th nestling-day. Nevertheless, parent birds brought foods as (3) 4 山 階 鳥 研 報 第11巻 第1号(No.54) Fig. 1. Daily change of feeding frequency of great tit. Open marks and x are number of visits per brood, and closed ones and cross are per nestling. Table 1. Daily change of feeding frequency (number of visits per nestling per day). In varied tit, A is number of visits and B is that of preys. mean of B/A=1.59 (4) 昭 和54年(1979)1月 Food and food consumption of nestling tits 5 frequently as before for successive two days after the predation and consequently number of visits per nestling was as twice as before (Fig. 1 and Tab. 1). KU-6 suffered in the evening of 13th nestling-day and nestlings were reduced from nine to six. Parents of KU-6 adjusted their feeding efforts to reduced number of nestlings, and therefore number of visits per nestling was not changed after predation. Varied Tit Only one observation at the nest of NO-7 (five nestlings) in Mt. Tachibanayama in 1977 is available. Fig. 2 and Tab. 1 show the daily change of the number of visit to the Fig. 2. Daily change of feeding frequency of varied tit. Open circles are number of visits per brood and closed ones are that of preys brought per brood. nest and of preys brought. Feeding frequency attained to 80 times/day (16 times/nestling/ day) by 4th nestling-day and thereafter levelled off. However, varied tit often brought more than one prey at a time, 1.59 prey/visit on average (Tab.