山階鳥研報 (J. Yamashina Inst. Ornithol.), 33: 1-14, 2001

Cooperative Breeding of the White-headed Leptopterus viridis, an Endemic in Madagascar

Masahiko Nakamura*, Satoshi Yamagishi** and Isao Nishiumi***

Abstract. Although the Vangidae provides one of the most striking examples of adaptive radiation in the avifauna of Madagascar, basic information on the breeding biology of each species is lacking. To examine the breeding system of the White-headed Vanga Leptopterus viridis, a species endemic to Madagascar, we studied the contributions made by males and females of nine pairs (involving nine banded individuals) to nest building, incubating, brooding, and feeding the young. The study was conducted from November to December in 1999 and 2000 at the Strict Nature Reserve of Ankarafantsika (Ampijoroa). Males defended dispersed territories, individual males paired with single females, and all observed copulations took place between females and males on whose territories they nested. During the nest-building stage, males and females provided material in equal proportion. Both sexes participated in incubating and brooding. During the nestling period, both sexes delivered food (mainly spiders and caterpillars) to the nestlings. In two of nine pairs, pairs and extra whose greater coverts were molting shared the territory and extra birds allopreened with pairs. Using the CHD gene sexing method, we determined that two of these extra birds were males. These extra males did not help feed young, but they mobbed that approached the nest. These results suggest that White-headed are cooperative breeders (of the singular-breeding type), where immature males assist in mobbing. Key words : biparental care, cooperative breeding, Madagascar, monogamy, White-headed Vanga. キ ー ワ ー ド:両 親 に よ る 子 の 世 話,協 同 繁 殖,マ ダ ガ ス カ ル,一 夫 一 妻,シ ロ ガ シ ラ オ オ ハ シ モ ズ.

Introduction The family Vangidae is endemic to Madagascar and comprises 14 (Langrand 1990) or 15 (Goodman et al. 1997) species. This family exemplifies adaptive radiation compa- rable to that of Galapagos finches and Hawaiian honeycreepers. Yamagishi & Eguchi (1996) observed the foraging behaviors of 13 vangid species, and documented their separation in foraging niches. In contrast to foraging ecology, little is known about the breeding ecology of each species, except the Schetba rufa (Yamagishi et al. 1995). The White-headed Vanga Leptopterus viridis is widely distributed in Madagascar,

Received 26 March 2001, Revised 16 April 2001, Accepted 22 May 2001. * Laboratory of Ecology , Department of Biology, Joetsu University of Education, 1 Yamayashiki- machi, Joetsu-shi, Niigata 943-8512, Japan. E-mail: [email protected] ** Laboratory of Ethology , Department of Zoology, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan. *** Department of Zoology, National Science of Museum, 3-23-1 Hyakunin-cho, Shinjuku-ku, Tokyo 169- 0073, Japan.

1 2 M. Nakamura, S. Yamagishi and I. Nishiumi except in the Central Plateau, occurring in secondary-growth forests at elevations between sea level and 2,000 m (Langrand 1990). Appert (1970) reported aspects of the breeding biology of this species, including biparental care during the nestling stage. However, the relative contribution of the sexes and detailed observations involving marked birds during different phases of reproduction have not been reported. The aims of this study are therefore: (1) to provide the first detailed information on the breeding biology of White-headed Vangas, and (2) to determine the breeding system by evaluating the parental investment of males and females throughout the reproductive cycle.

Study Area and Methods

This study was conducted in the eastern part of the Strict Nature Reserve of Ankarafantsika(Ampijoroa,16°15'S,46°48'E, ca.200 m above sea level, about 110 km southeast of Mahajanga), from November to December 1999 and 2000. The eastern part of the reserve contained villages, forest stations, and campsites, around which tall trees

(Eucalyptus sp. [Myrtaceae], Tamarindus indica[Fabaceae]and Hura crepitens[Euphor- biaceae])were planted. To examine home ranges, we walked along trails at random from 0500 h to 1000 h almost every day between 6 and 19 November 1999. When we located individuals, we recorded their positions and behaviors on a map. Home ranges were delineated by connecting the outermost observation points with straight lines. We observed a total of nine breeding pairs: four in 1999 and five in 2000. White- headed Vangas are sexually dimorphic; males have white heads, whereas females have gray heads. Of 17 individuals, five males (Ml, M2, M3, M4, and M5), two females (F1 and F2), and one individual whose sex was unknown (U1) were captured in mist nets that were set up around nest trees during the nest-building and incubation periods. To facilitate capturing birds, we set a speaker in front of the mist nets and played back the "yippie-hoo" songs (Langrand 1990) of males for 3 min. We also captured three nestlings (two in 1999, one in 2000). Each received a unique combination of colored leg bands. Unbanded birds were referred to by their sex followed by a lowercase letter, e.g., Ma (unbanded male a), Fa (unbanded female a), and Ua (unbanded bird a, sex unknown). For captured birds of unknown sex, we used the CHD (chromo-helicase-DNA-binding protein) gene sexing method to determine the gender. We collected blood (0.1 ml) from a brachial vein of each individual, and preserved these samples in Queen's lysis buffer (0.01 M Tris, 0.01 M NaCl, 0.01 M EDTA, and 1 % n-lauroylsarcosine, pH 7.5; Seutin et al. 1991) until DNA extraction could take place. The sexes of captured birds were determined using Ellegren's (1996) molecular sexing method (see more details in Naka- mura & Nishiumi 2000). Nine nests were found and designated as Nests A to I. The height above ground of each nest and the diameter at breast height (DBH) of the nest trees were measured. To examine the relative contributions of the sexes to reproductive efforts, we studied the following activities: (1) nest building (Nests B and D), (2) egg laying (Nests B and D), (3) time budgets of incubation (percentage of time that individuals spent incubating, Cooperative Breeding of White-headed Vanga 3

Nests A-G), (4) time budgets of brooding (percentage of time that individuals spent brooding, Nests A, B, E-I), (5) feeding frequency (times/h/brood; Nests A, B, E-I) and (6) nest defense (all nests). We also examined food items given to the young (Nests A, B, E-I). An incubation session was defined as having started when a focal individual began incubating eggs and ending when that individual left the nest. Similarly, a brooding session was defined as starting when a focal individual brooded nestlings and ending when it left the nest. Direct observationswere made using a 20 X spottingscope(for a totalof 70 h) whereas indirectobservations were made with a SONY video Hi8 camera(CCD-TRV66; for a totalof 143 h)from a vantage point thatallowed a good view of the nest(5-15m). We observed nestsfor a totalof 213 h(9.5 h at two nestsat the nest-buildingstage;5.5 hat two nestsat the egg-layingstage; 95 h at seven nestsat the incubationstage; 103 h at seven nestsat the nestlingstage). Direct and indirectobservations were usuallymade between 0500 h and 1100 h, sometimes from 0500 h to 1700 h. Nests were visitedevery day to examine breedingschedules. The contentsof Nests B and E could be observed by a mirror attachedto an extendiblepole. All statistical tests were conducted with StatView 5.0 (SAS 1998). Mean values in the text are reported with the standard error (±SE).

Results

Nests The characteristics of nest trees are summarized in Table 1. Nests were bowl-shaped and covered with spider webs, and usually located 6-19 m above the ground on a horizontal branch. We collected Nest A during the nestling period after strong winds had blown it from the nest tree. The dimensions of this nest were as follows: exterior diameter, 14 cm; interior diameter, 8.5 cm; exterior bowl depth, 8 cm; interior bowl depth, 6 cm. A pair of Sickle-billed Vanga Falculea palliata bred about 5 m below Nest D in the same tree.

Table 1. Nest tree (scientific name), height (m above the ground), diameter at breast height (DBH), and the composition of the breeding unit in each nest.

* M= Male , F= Female, N= Nestling, U= Unknown sex bird. Nestlings of each pair are given in parentheses. Banded and unhanded individuals were referred to by their sex and age followed by figure and a small letter, respectively. 4 M. Nakamura, S. Yamagishi and I. Nishiumi

Fig. 1. Plumages of the adult male (A), adult female (B), and extra bird (C) at Nest E. Cooperative Breeding of White-headed Vanga 5

Fig. 2. Distribution of nests and home ranges of White-headed Vangas. Solid circles represent nest sites, stars indicate the locations of observed confrontations between individuals, and triangles denote the positions of speakers used for playbacks. Owners of the home ranges are given in parentheses.

Composition of breeding unit In 1999, individual males paired with single females at four nests (Nests A-D, Table 1) To capture breeding individuals in 2000, we played back the songs of males near five nests (Nests E-I, Table 1) during the incubation and nestling periods. Males responded to playbacks at all nests. Additionally, three extra birds (U1 and Ua at Nest E, N1 at Nest F, see Table 1) responded to the playbacks. The body coloration of U1 (C in Fig. 1) differed with that of an adult male (M5, A in Fig. 1) but was similar to that of an adult female (F2, B in Fig. 1), with a gray head, nape, cheeks, and throat. However, the wing color was not black but gray, and the greater coverts were molting (Fig. 1). We could not capture Ua and N1, but their plumages were similar to those of U1, and the greater coverts were molting. N1 was an offspring of parent (Ml and Fa) at Nest A (see Table 1). The CHD gene sexing method revealed that two of the extra birds (U1 and N1) were male. We did not know whether Fa and Fd were the same bird, because Fa was not banded in 1999.

Space use Four nests (A-D) were located about 100 m from each other in 1999 (Fig. 2). Average home range size was 1.2 ± 0.10 ha (n = 4). When we found these nests, nest building had already commenced in Nests B and D, and incubation had begun at Nests A and C. Each pair shared a home range, but none of the home ranges of the observed birds overlapped (Fig. 2). Eight confrontations were observed at the peripheries of the home ranges (Fig. 2). All confrontations involved males chasing males. We played back songs 22 times at 12 points (Fig. 2). In all cases, males within their home ranges responded aggressively to the speakers. Setting the speakers near the nests allowed us to capture the 6 M. Nakamura, S. Yamagishi and I. Nishiumi males easily, because they readily flew into the mist nets. We found the dead body of M3 in his home range on 14 November 1999 (during the incubation period). His mate (Fb) abandoned the nest on 16 November, and disappeared on 20 November. Their home range was not subsequently occupied by other individuals. In 2000, we did not examine home ranges exactly. However, five nests (E-I) were located about 100 m from each other. When other individual White-headed Vangas approached Nests E and F, resident males and extra birds chased them aggressively (six times at Nest E, four times at Nest F).

Nest building During 9.5 h of direct observation, we noted that nesting materials were brought to Nests B and D on 140 occasions (data were pooled for the two nests). Building materials consisted of plant fibers, spider webs, and twigs. Both sexes participated in nest building. At Nest B, M2 provided material on 29 occasions (44%), compared to 37 occasions (56%) by F 1 within 4.5 h (data pooled for two days). Similarly, at Nest D, M4 provided material on 33 occasions (45%), compared to 41 occasions (55%) by Fc within 5.0 h. This was not significantly biased from the assumption of equal provisioning by male and female at either nest (Nest B: G = 0.49, P = 0.49; Nest D: G = 0.43, P = 0.51). We have no precise data on the duration of nest building. Construction of Nest B had already begun by 1 November (S. Asai, pers. comm.) and was complete on 10 November. Thus, the parents spent at least 10 days constructing the nest. Because Nest D was found later, only 3 days of nest building activities were observed.

Copulation During the nest-building stages, we observed five courtship displays, involving two copulations, around Nest B, and four courtship displays, also involving two copulations, around Nest D. Moreover, we observed one courtship display involving one copulation during the incubation period (13 days after the first egg was laid) around Nest E. All observed copulations occurred between the nesting females and the males on whose home ranges they were nesting. All matings began with the female courting the male. The female typically crouched on a branch, fluffed her body feathers, and shook her wings and tails, resembling the begging behavior of the young. In contrast, the male performed no sexual displays, but rather appeared to watch the soliciting female. The male approached the side of the soliciting female and mounted her back.

Egg laying and clutch size During the egg-laying period, only females provided nesting materials at two nests (Nest B, seven occasions for 2.0 h; Nest D, 10 occasions for 3.5 h). The male associated closely with the female during this period. Nest B contained four eggs, and F 1 laid one egg per day. Nests D and E, each contained three eggs, but the eggs at Nest D were blown from the nest tree on 1 December (during the incubation period). Eggs had a reddish-white base color, with large, dense, gray-red speckles near the pointed end and maroon spots around the blunt end. We were Cooperative Breeding of White-headed Vanga 7

Fig. 3. Incubation time budgets of male and female White-headed Vangas at seven nests. Open bars represent males; hatched bars represent females. The number of incubation sessions is shown above the bars. Observation times (hours) each day are given in parentheses. unable to determine the clutch sizes of Nests A, C, and F-I.

Incubation Males and females took turns incubating, spending a total of 97.9 ±0.7% (n =19 days; Fig. 3) of their time. On some days (e.g., 26 and 29 November at Nest B), males incubated longer than female (Fig. 3). This was because the number of incubation sessions of males was larger than that of females (Fig. 3). Similarly, when females had more incubation sessions (e.g., 22 November at Nest B), they incubated longer than males (Fig. 3). However, the differences in incubation session between the sexes were not significant in five nests (Table 2). The change of incubation task was often preceded by songs or soft vocalizations ("kyuw, kyuw") by arriving adult. The incubating adult flew away as the vocalizing bird arrived at the nest. At Nest E, we observed the change of incubation task 33 times. In 18 of the 33 changes, extra birds (U1 and Ua) followed a parent (eight times with M5, ten times with F2), but they never attempted to incubate. At Nest F, we observed the change of incubation task eight times. In four of the eight changes, N1 followed M1 (twice) and Fd (twice), but N1 never incubated. U1, Ua and Nl often allopreened with pair males and females when the incubating bird had left the nest. We were unable to locate Ub after 8 M. Nakamura, S. Yamagishi and I. Nishiumi

Table 2. Comparison of incubation sessions (min) between males and females in seven nests. Significant differences with two-tailed Mann-Whitney U-test.

* Test could not be done because of small sample size .

Fig. 4. Brooding time budgets of male and female White-headed Vangas at seven nests. Open bars represent males; hatched bars represent females. Nestling age is given in days after hatching (day 0 is the hatching date). The number of brooding sessions is given above the bars. Observation times (hours) each day are given in parentheses. Cooperative Breeding of White-headed Vanga 9

Table 3. Comparison of brooding sessions (min) between males and females in four nests. Significant differences with two-tailed Mann-Whitney U-test.

Fig. 5. Feeding frequency of male and female White-headed Vangas in relation to nestling age. Open bars represent males; hatched bars represent females. Nestling age is given in days after hatching. Observation times (hours) each day are given in parentheses above the bars.

19 November. The pair at Nest B began to incubate 2 days after the first egg was laid, and all eggs hatched 19 days after laying. We could not determine the exact incubation period at Nests A and C-I. 10 M. Nakamura, S. Yamagishi and I. Nishiumi

Brooding Nests A and E-I contained three nestlings, and Nest B had four nestlings (Table 1). Nestlings were brooded by either sex (Fig. 4). U1 at Nest E and N1 at Nest F followed the pairs when they arrived to brood nestlings or left the nest, but they never attempted to brood. Overall, females brooded more often and for longer periods than males (Fig. 4). Parents spent 68.5% of the time brooding at 3 days after hatching at Nest A, 71.4% after 4 days at Nest B, and 82.1% after the first day at Nest E (Fig. 4). However, for all nests, both parents spent less time brooding as the nestlings grew (Fig. 4). Similarly, the number of brooding sessions of each sex decreased with the growth of the nestlings, and the parents did not brood the nestlings after 18 days (e.g., Nests B and G-I; Fig. 4). The differences in brooding sessions between the sexes were not significant in four nests (Table 3).

Feeding frequency and duration Both sexes delivered food to the nestlings during the nestling period (Fig. 5). At all nests, the feeding frequency of males was higher than that of females, regardless of the age of the nestlings, except for age 21 days at Nest B (Fig. 5). Two of four young left Nest B at 22 days after hatching. When both sexes went in and out of Nests E and F to deliver food, extra males followed the pairs, but they never delivered food to the nestlings (Fig. 5). We observed 38 cases in which the male gave food to the female and the female offered it to the nestlings, but the extra males did not give food to the pairs. However, allopreening between both sexes and extra males (14 cases) and between both sexes (12 cases) was observed near the nests (data pooled for the two nests).

Because the feeding behaviors at Nests A and B were recorded by video camera, the exact duration of feeding could be determined. The average duration of feeding by Fa

(34.8±3.8sec, n=63)was significantly longer than that by M 1(22.5±1.5 sec, n=100) at Nest A(Mann-Whitney U-test, z=3.18, P<0.01). However, it was similar for both sexes at Nest B(M2,23.6±1.6 sec, n=184;F1,26.0±1.6 sec, n=175;z=1.55, P=0.12). We could not determine the nestling period (i.e., the time from hatching to leaving the nest) at Nest A, because the nest and nestlings were blown from the nest tree. After falling, three nestlings climbed a tree near the nest, and the parents continued to feed them for at least 14 days. The nestling period at Nest B ranged from 22 to 24 days. Two young left this nest 22 days after hatching, one after 23 days, and one after 24 days. When the young fledged, they flew between the nest and other trees. After fledging, the young remained within the home range of the parents, and the pair continued to feed them for at least 11 days. However, we did not know the exact duration of post-fledging parental care. We could not determine the nestling period at Nests E-I because the nestlings disappeared.

Nest defense When potential predators, such as the Madagascar Coucal (Centropus toulou ), Crested Coua (Coua cristata), Crested Drongo (Dicrurus forficatus), Brown lemur Cooperative Breeding of White-headed Vanga 11

(Eulemur fulvus), snakes, or chameleons, approached the nest during the incubation and nestling periods, both sexes gave warning calls and mobbed them (54 cases at Nests B, C, D, G, H, and I). At Nests E and F, extra birds (U1, Ua, and N1) as well as both parents approached and mobbed the potential predators (26 cases, data pooled for the two nests). In mobbing, the males and extra birds were the most aggressive, whereas females gave warning calls but did not come close to the potential predators. After mobbing, both sexes often attempted allopreening (26 of 54 cases). Allopreening was observed between both sexes and extra males after mobbing (14 of 26 cases).

Nestling diet Throughout 33 h of direct observation at seven nests (Nest A, B, E-I), we observed 234 prey items being fed to nestlings (data pooled for the seven nests). However, it was difficult to identify all food items, both because food was usually masticated by the parents before offering it to the nestlings, and because feeding was very quick. Thus, we were only able to identify 79 food items. Spiders (52%) and caterpillars (30%) accounted for most of the identified prey. Other items included grasshoppers (7%), crickets (5%), small chameleons (4%), a small cockroach (1%), and a cicada (1%).

Discussion The dispersal pattern of individuals is a factor in determining the mating system of a given species, and monogamous birds usually hold a territory that is shared by both sexes (Davies 1991). Male White-headed Vangas defended dispersed areas, individual males paired with single females, and all observed copulations occurred between females and the males in whose territories they defended (Fig. 2). The home ranges of the four pairs did not overlap, and confrontations between males were observed only at the peripheries of their home ranges (Fig. 2). Thus, we interpreted the home ranges as being territories. Territories appeared to be defended mainly by males and extra males, who responded more to playbacks and were more aggressive in confrontations and mobbings than females. Our results suggest that male and female White-headed Vangas contribute equally to overall breeding activity. During the nest-building stage, males and females provided material in equal proportions. Both sexes participated in incubating and brooding (Figs. 3 and 4). After the incubating male (M3) died, the female (Fb) abandoned their nest, suggesting that biparental incubation may be necessary for successful breeding in this species. During the nestling period, both sexes fed nestlings (Fig. 5). The degree of investment by each parent differs considerably between social mating systems such as monogamy, polygyny, and polyandry (Clutton-Brock 1991, Davies 1991). In monogamous birds, biparental care is common, and males are more active in territorial defense (Clutton-Brock 1991). Monogamy with biparental care is predicted to occur when extensive care by males and females is necessary for successful breeding (Clutton- Brock 1991, Ligon 1999). Seven out of nine pairs of White-headed Vangas whose breeding activities we observed fulfilled these conditions and had no helpers, similar to 12 M. Nakamura, S. Yamagishi and I. Nishiumi

what has been reported in Rufous Vangas (Yamagishi et al. 1995) and what may occur in Chabert's Vangas Leptopterus chabert (Appert 1970). However, two of nine pairs did have extra birds. By far the most common form of cooperative breeding in birds is the helper-at-the- nest type, where younger non-breeding individuals provide food for the young of a monogamous breeding pair, and also aid in sentinel duties or territorial defense (Smith 1990). Helpers are usually the male offspring of at least one of the breeders (Brown 1987). The two extra birds in our study were males, and one (N1) was a son of M1 at Nest A. However, our small sample size did not allow us to make generalizations regarding the origin of extra males in this species. The allopreening observed between pairs and extra males suggests that they may have been related. However, extra males never helped to feed young, and only aided in mobbing or defending territories. The mobbing behavior of extra males appears to increase the protection against predation, particularly in the region where frequent nest failures have been observed in other vangas (Rufous Vanga, Yamagishi et al. 1995; Van Dam's Vanga damii, Mizuta et al. 2001; Hook-billed Vanga Vanga curvirostris, Rakotomanana et al. 2001) and other species (e.g., Madagascar Paradise Flycatcher Terpsiphone mutata, Mizuta 2000), indicating high predation pressure. Thus, we consider extra males as helpers and propose that the breeding system of the White-headed Vanga is cooperative, categorized as a territorial, singular-breeding type (Brown 1987). The extra males were presumed to be immature because of their female-like plumages and molting wings (Fig. 1). Gonads are usually undeveloped during molting (Payne 1972), so it is unlikely that the extra birds can help in the breeding activity of pairs or breed on their own. However, to describe the social structure of White-headed Vangas in more detail, more nest observations, and analyses of kinship between group members, and of the relationships between pairs and young during the non-breeding season are necessary.

Acknowledgments We are grateful to the director, Albert Randrianjafy, and other staff of the Botanical and Zoological Park of Tsimbazaza for their cooperation in this project. Our heartfelt thanks go to the staff of Conservation International for accommodations and facilities at the Ampijoroa Forest Station and to the Direction Generale des Eaux et Forets, Associ- ation Nationale pour la Gestion des Aires Protegees, which made this study possible. We thank Shigeki Asai, Takayoshi Okamiya and Masami Hasegawa for their assistance in the field. We also express our thanks to two anonymous reviewers for their many constructive comments and suggestions. This study was supported by a Grant-in-Aid for Scientific Research (A) of the Ministry of Education, Science, Sports and Culture (No.11691183).

References

Appert, O. 1970. Zur Biologic der Vangawurger (Vangidae) Sudwest-Madagaskars. Ornithol. Beob. 67: 101- 133. Cooperative Breeding of White-headed Vanga 13

Brown, J. L. 1987. Helping and communal breeding in birds, pp. 15-25. Princeton University Press, Princeton. Clutton-Brock, T. H. 1991. The evolution of parental care. pp. 131-152. Princeton University Press, Princeton. Davies, N. B. 1991. Mating systems. In Behavioural ecology: an evolutionary approach. Krebs, J. R. & Davies, N. B. (Eds.), pp. 263-294. Blackwell Scientific Publications, Oxford Ellegren, H. 1996. First gene on the avian W chromosome (CHD) provides a tag for universal sexing of non-ratite birds. Proc. R. Soc. Lond. B 263: 1635-1641. Goodman, S. M., Hawkins, A. F. A. & Domergue, C. A. 1997. A new species of vanga (Vangidae, Calical- icus) from southwestern Madagascar. Bulletin of the British Ornithologists' Club 117: 5-10 Langrand, O. 1990. Guide to the birds of Madagascar, pp. 290-302. Yale University Press, New Haven and London. Ligon, J. D. 1999. The evolution of avian breeding systems. pp. 259-286. Oxford University Press, Oxford. Mizuta, T. 2000. Intrusion into neighboring home range by male Madagascar Paradise Flycatchers Terpsi- phone mutata: a circumstantial evidence for extra-pair copulation. J. Ethol. 18: 123-126. Mizuta, T., Nakamura, M. & Yamagishi, S. 2001. Breeding ecology of Van Dam's Vanga Xenopirostris damii, an dndemic species in Madagascar. J. Yamashina Inst. Ornithol. 33: 15-24. Nakamura, M. & Nishiumi, I. 2000. Large variation in the sex ratio of winter flocks of the Alpine Accentor Prunella collaris. Jpn. J. Ornithol. 49: 145-150. Payne, R. B. 1972. Mechanisms and control of molt. In Avian biology, Vol. 2. Farner, D. S. & King, J. R. (Eds.), pp. 104-155. Academic Press, London. Rakotomanana, H., Nakamura, M. & Yamagishi, S. 2001. Breeding ecology of the endemic Hook-billed Vanga Vanga curvirostris in Madagascar. J. Yamashina Inst. Ornithol. 33: 25-35. SAS. 1998. StatView for Macintosh, version 5.0. SAS Institute, Cary, North Carolina. Seutin, G., White, B. N. & Boag, P. T. 1991. Preservation of avian blood and tissue samples for DNA analyses. Can. J. Zool. 69: 82-90. Smith, J. N. M. 1990. Summary. In Cooperative breeding in birds: long-term studies of ecology and behavior. Stacey, P. B. & Koenig, W. B. (Eds.), pp. 593-611. Cambridge University Press, Cambridge. Yamagishi, S. & Eguchi, K. 1996. Comparative foraging ecology of Madagascar vangids (Vangidae). Ibis 138: 283-290. Yamagishi, S., Urano, E. & Eguchi, K. 1995. Group composition and contributions to breeding by Rufous Vangas Schetba rufa in Madagascar. Ibis 137: 157-161.

マダガ スカル特産 シ ロガ シラオオハ シモズLeptopterus viridisの協 同繁殖

マ ダガスカル島 に生息す るオオハ シモズ科鳥類 は著 しく適応放散 した種群 に も関わ らず,各 種鳥類の基本的 な繁殖生態 はほとん どわか っていない。 オオハ シモズ科鳥類 の一種 であ るシロ ガ シラオオハ シモズの配偶 システムを調べ るため,1999年 と2000年 の11月 か ら12月 にマ ダ ガ スカル西部地域,ア ンカ ラファンチカ厳正 保護 区(ア ンピジュルア)に おいて,9個 体の識 別 個体を含む9番 いの雌雄の造巣,抱 卵,抱 雛及 び育雛活動 を観察 した。雄 は分散 したなわば り を所有 し,1羽 の雌 と番 いを形成 した。交尾 は番い間で行なわれ,な わば りの中で観察 された。 造巣期 には雌雄 は同 じ割合で巣材 を運搬 した。抱卵,抱 雛 とも雌雄 が行 ない,育 雛期 には雌雄 共同で雛 に給餌 した(主 な餌 はクモとチ ョウ目の幼虫)。9番 い中2番 いで は大 雨覆が換羽中の 個体がなわば りを共有 し,番 いの雌雄 と相互羽づ くろいを した。CHD遺 伝子 による性 判定の 結果,換 羽中の個体 は雄で ある ことが わか った。換羽 中の雄個体 は巣 に接近 す る動物 に対 して 番い とともにモ ビング したが,抱 卵,抱 雛及 び雛 への給餌 を手伝 うことはなか った。 これ らの 結 果よ りシロガ シラオオハ シモズの配偶 システムは一夫一妻 を基本 と し,未 成熟雄個体が番 い とともに巣を防衛す る協同繁殖 と考 えた。 14 M. Nakamura, S. Yamagishi and I. Nishiumi

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