Azure-winged Magpie Cyanopica Cyana Research Articles

Effect of Japanese lesser sparrowhawks Accipiter gularis on the nest site selection of azure-winged magpies Cyanopica cyana through their nest defending behavior

Effect of Japanese lesser sparrowhawks Accipiter gularis on the nest site selection of azure-winged magpies Cyanopica cyana through their nest defending behavior

Characteristics of brood parasitism by Common Cuckoos on Azure-winged Magpies, as illustrated by video recordings

ABSTRACT To clarify the influence of host aggression on the Common Cuckoo Cuculus canorus, the cuckoo's parasitic behaviour was compared between a new host, Azure-winged Magpie Cyanopica cyana, and an old host, Great Reed Warbler Acrocephalus arundinaceus. Magpies exhibited less aggression towards cuckoos than did the warblers, and hardly attacked cuckoos at the nest. Cuckoos spent longer in the vicinity of nests while parasitizing magpie nests than when parasitizing reed warbler nests; possibly because of the magpie's lower aggression. Cuckoos parasitized magpie nests later in the day than reed warblers, despite the lower aggression of the magpies. The effect of host aggression on cuckoo parasitic behaviour and the adaptive significance of parasitic behaviour are discussed.

Cost of Nest Defense in Azure-Winged Magpies

I studied costs of nest defense in Azure-winged Magpies Cyanopica cyana in Tokyo, Japan in 1994 and 1995. I compared time devoted to nest defense, frequency of nestling feeding, and number of fledglings of magpies breeding near nests of Japanese Lesser Sparrowhawk Accipiter gularis and magpies breeding far from such nests. Because the hawks attack potential predators, magpies near a hawk's nest did not defend their nest, whereas magpies breeding far from a hawk's nest defended their nest. Feeding frequencies and number of fledglings were greater near a hawk's nest than far from it. Because nest defense incurs a cost in the form of decreased feeding time, Azure-winged Magpies far from a hawk's nest probably provided less food to their chicks and therefore raised fewer fledglings than those breeding close to a hawk.

Reproductive skew and the threat of eviction: a new perspective

Most recent models of the partitioning of reproduction attempt to explain patterns of skew on the assumption that dominant individuals have complete control over breeding opportunities within the group, but may nevertheless concede a share of direct reproduction to subordinates as an incentive to remain peacefully in the association. Although these models may be applicable to some animal societies, we argue that they fail to provide a comprehensive theory of skew. Instead, we suggest that subordinates may often be able to claim unsanctioned reproduction for themselves, but will be forced to exercise a degree of reproductive restraint lest they incite ejection by the dominant. Reproductive skew, in other words, may reflect the threat of ejection (inducing subordinate restraint) rather than the threat of subordinate departure (inducing reproductive concessions by dominants). We present a simple ESS model of reproductive skew under these circumstances, which demonstrates that a shift in emphasis from reproductive concessions by dominants to reproductive restraint on the part of subordinates, radically alters the predictions of skew models. High group productivity, high relatedness and (when group members are related) strong ecological constraints are all expected to lead to reduced skew (the opposite conclusions to those of previous, concession-based analyses). The reason is that these factors reduce the benefits (or increase the costs) of ejection to the dominant, who therefore does best to tolerate more subordinate reproduction.

Movements, Space Use and Social Organization of Radio-tracked Common Cuckoos during the Breeeding Season in Japan

The movements, space use, and social organization of a colour-marked Common Cuckoo Cuculus canorus population were investigated during the 1984-1993 breeding seasons in central Japan. Of 333 captured cuckoos, 81 had radio transmitters attached to them. Excluding unknown birds (8.7%), the male : female ratio was 1.25 : 1.00. Radio-tracking showed that each cuckoo had a distinct breeding area and a distinct feeding area, and commuted between them every day. Birds spent most early mornings in host-rich habitats such as the Chikuma River, and then visited neighboring mountains or suburbs for foraging. The average time spent in the breeding area was 9.0 ± 0.8 hours per day (58.2 % of the daytime hours) for males and 8.7 ± 0.7 hours (56.3 %) for females. All males visited their breeding areas just after dawn, but the peak time for females was one hour later. After the early morning peak, the rate decreased gradually until early afternoon and increased again in the late afternoon with both sexes. The main activity of males in the breeding area was singing, and they sang between 19.8 % and 40.2 % of the total time they spent there. Each male sang in a restricted area and the average size of the song area was 40.9 ± 4.9 ha. However, male song areas had a large overlap, especially at the groves of acacia trees around which were many host nests. Males sometimes made short visits outside their song areas. The average size of males' breeding area, including these short visits, was 67.5 ± 8.9 ha. There were three types of females corresponding to three major hosts: the Great Reed-warbler Acrocephalus arundinaceus, the Bull-headed Shrike Lanius bucephalus and the Azure-winged Magpie Cyanopica cyana. Each female cuckoo in this study specialized on a single host species. The breeding areas of females overlapped considerably both "inter" and "intra" between different female groups. The average size of the females' breeding areas was 63.6 ± 8.5 ha. However, magpie-cuckoo females had significantly larger areas than warber-cuckoo females. The cuckoos rarely fed in their breeding areas. During their absence from the breeding area, most cuckoos visited nearby mountains, but some cuckoos, breeding at sites far from the mountains, visited suburbs for feeding. The average size of a feeding area in the mountains was 23.7 ± 5.7 ha for males and 27.6 ± 6.8 ha for females. By contrast, a female which foraged in the suburbs had a large feeding area (327.0 ha). The number of visits per day was related to the distance between the breeding area and feeding area. Cuckoos foraging at more distant sites visited these sites only once per day, while cuckoos foraging at closer sites visited them more frequently. There was a positive relationship between distance to feeding area and mean times spent per visit. There was a negative relationship between distance to feeding area and total feeding time per day. Cuckoos roosted solitarily in both their breeding and feeding areas. Roosting sites in the mountains changed almost every day, but some cuckoos roosting at the river or in the suburbs often used the same sites repeatedly. Roosting in the breeding area was more commons with males than with females, but it decreased in both sexes as the season progressed. The average size of a home range was 3.02 ± 0.28 km2 for males and 3.26 ± 0.40 km2 for females. In this paper, we discuss the following three points: (1) The separation of the breeding area and the feeding area is a common characteristic of the cuckoo and it is closely related both to the cuckoo's parasitic breeding and to its special feeding habits; (2) There are costs attendant with leaving the breeding area in order to visit a feeding area.

The caching behaviour of Japanese Lesser Sparrowhawks Accipiter gularis during the breeding season

We investigated the caching behaviour of Japanese Lesser Sparrowhawks Accipiter gularis during the breeding season in Tokyo and Utsunomiya, central Japan. Observations were made from April to July 1987-1993 in Tokyo and 1991-1993 in Utsunomiya. A total of 46 caching behaviours were observed. All of the prey items cached were small and medium-sized birds, especially Tree Sparrows Passer montanus (65.2%, 30 of 46). Hawks cached prey that were half eaten by females, and prey which was not taken by the female in attempted prey exchanges initiated by the male. Many caches were carried out in the incubation and early nestling periods. Hawks stored prey on gnarled, broken twigs and leaf clumps on horizontal branches 7-8m in height and within a few meter to 50m apart from the food exchange site. Some birds used a few definite sites, and others used many places within a range of 50 × 30 m as caching sites. When hawks flew to caching sites with prey, they placed the prey carefully, and push it several times with their legs and beak. At least 11 stored items were retrieved within 3-247 min. (mean ±S.D., 78.5 min. ±73.2) after caching. Although 8 stored items were stolen by Azure-winged magpies Cyanopica cyana, most cached prey may be retrieved.

Note on stealing cached prey of a Japanese Lesser Sparrowhawk Accipiter gularts by Azure-winged Magpies Cyanopica cyan

I observed that Azure-winged Magpies Cyanopica cyana stole cached prey of a Japanese Lesser Sparrowhawk Accipiter gularis at a small wooded park in Utsunomiya, central Honshu in late May 1992. The breeding stage of this hawk's pair was during 1 to 5 days after hatching. A male hawk cached the surplus prey that had been caught more frequently than female was needed. The caching behavior was observed 7 times during the observation period of a total 440 minutes, and all of them were stolen by magpies. All the prey items were Tree Sparrows Passer montanus. Azure-winged Magpies took away the sparrows as soon as the hawk flew away from caching sites. Because the hawk's foods are plentiful in this area and the magpies did not rob the prey directly from the hawk, it is unlikely that Azure-winged Magpies have a serious effect on breeding success of Japanese Lesser Sparrowhaks.

Brood Parasitism by the Cuckoo Cuculus canorus in Japan and the Start of New Parasitism on the Azure-winged

Potential host species of the Cuckoo in Japan, frequency of parasitism in central Honshu, and the process of the establishiment of a new parasitic relation with the Azure-winged Magpie Cyanopica cyana were studied both by literature and field work.1) Twenty-eight species have been recorded as cuckoo hosts in Japan and twelve species of them are major hosts. The numbers of host species were greatest in central Honshu (20 species).2) The mean rates of parasitism by the cuckoo on a total of six major hosts were more than 10 in Nagano Prefecture, central Honshu. The highest parasitism rate was 79.6% on a local popula-tion of the Azure-winged Magpie.3) Dynamic changes of parasitic relations between cuckoos and the hosts occurred during the last 60 years. About 15 years ago, the Cuckoo began to parasitize the Azure-winged Magpie. The parasitism rate increased rapidly and has now expanded to almost all of the breeding range of the Magpie. Conversely, the Siberian Meadow Bunting Emberiza cioides has become a rare host.4) The new parasitic relation with the magpie started as the result of their range overlap after their range expansions. In most regions, the cuckoo parasitism on the magpie did not start soon after their range overlap, but took about 10 to 15 years.5) The characteristics of the cuckoo parasitism in Nagano Prefecture and the process of the establishment of new parasitic relation were discussed.

Characteristic Features of Group Living Life of the Azure-winged Magpie Cyanopica cyana

1) The social system of Azure-winged Magpies Cyanopica cyana was studied at Hizume, Nagano City, from 1983 to 1984, and at Kawanakajima, Nagano City, from 1962 to 1965 and inwinter of 1983.2) The six months from April to September were defined as the breeding season, because pairs with or without their fledglings were observed during this period.3) In the non-breeding season, flocks consisting of about 20 magpies were formed and the size of each flock was stable throughout the day.4) In the non-breeding season, all members of a flock always roosted together. In winter and spring, different flocks sometimes roosted together without any antagonistic behavior.5) The home range of Hizume flock was 1.2 km long and 0.9 km wide, and included 18 units of premises consisting of some houses and surrounding woods. Magpies spent longer time in premises with closed woods than those with sparse woods.6) Home ranges of flocks seemed to coincide nearly with territories, because the home ranges overlapped little with each other and chases were observed around the boundaries of the ranges.7) Flocks broke up into some pairs, non-breeding adults and subadults in the breeding season. At Hizume, nests of pairs belonging to the same winter flock were built 10-20 m apart from each other in a unit of premises, and the flock members visited the nests without any antagonistic behavior.8) The fledging rate was nearly 50%. Families consisting of pairs and their fledglings were observed from mid-May to mid-September. Family members moved and roosted together in the nesting woods about one month after fledging.9) There was no antagonistic behavior between families of the same flock. Some adults which had failed in breeding joined families, and one subadult fed fledglings as a helper.10) Even in the breeding season, not only pairs but also some non-breeding adults and subadults of the same flock sometimes moved or roosted together. They showed defensive behavior against conspecific intruders or natural enemies such as domestic cats and crows.11) As a conclusion of comparison among group-living birds, the Azure-winged Magpie was considered as a typical species which formed stable flocks throughout the year.

Heavy Brood Parasitism by the Common Cuckoo Cuculus canorus on the Azure-winged Magpie Cyanopica cyana

(1) In the course of a study of the social behavior of Azure-winged Magpies Cyanopica cyana in 1984 and 1985 at Azumino, Nagano Prefecture, we found heavy brood parasitism by Common Cuckoos.(2) A total of 31 nests out of 41 (75.6%), among core groups and 15 nests of 30 (50.0%) in secondary groups were parasitized. Eight nests contained two, and one contained three cuckoo eggs.(3) The earliest magpie nests, in which the first egg was laid during the middle of May, were parasitized less frequently (11.1%) than later nests (68.8%).(4) Cuckoo eggs (23.4×17.4 mm, n=13) were smaller than Azure-winged Magpie eggs (27.67×20.16 mm, n=16).(5) Azure-winged Magpies suffered heavy brood parasitism by Common Cuckoos probably because of the short history of the host-parasite relationship between them, which is as a result of a recent expansion of their breeding areas in Nagano Prefecture.