Birds of a wide range of species show characteristic movements of their tail, often called tail flicking, tail wagging or tail flashing. Tail flicking refers to vertical up-and-down movements of the tail, while tail flashing is defined as a horizontal movement, often including tail spreading. Here, I review proposed functions of such behaviour. Most relate to communication with conspecifics, predators or prey. Tail flashing may induce movement of the bird's prey that makes the prey more vulnerable to capture (‘prey-flushing’). Tail movements may signal to a predator that the signaller has detected it (‘perception advertisement’), or that the signaller is particularly alert or otherwise difficult to catch (‘quality advertisement’). Further, it may warn conspecifics of predators (‘alarm signal’), or it may advertise quality as a mate, signal social status, or aid in flock cohesion. This behaviour may, possibly, though it seems unlikely, represent a cue rather than a signal in that it benefits the receiver, but not the signaller. For each postulated function, I develop predictions stemming from that function, and interpret the available empirical evidence in the context of these predictions. I finish by synthesising our current state of knowledge and by identifying the future empirical studies that would most improve our understanding of this widespread but unjustly neglected avian behaviour.
Older or heavier Rhinoceros Auklet Cerorhinca monocerata chicks are less likely to remain in their nest during pre-fledging mass recession. Older or heavier chicks have longer wings but the individual variation in wing length at fledging is small. To identify proximate triggers of fledging from a mix of candidates when chicks experienced mass recession, we selected 30 nest boxes each containing a chick and provided half of them with 30-60 g of supplementary foods in an attempt to expand their variation in growth rate. When chicks reached the minimum wing length required for fledging (130 mm), we stopped all provisioning (supplementary and parental) by closing a hatch on the nest box entrance thereby simulating mass recession and inducing fledging. With these treatments, we examined whether timing of fledging (=duration of mass recession) was only triggered by wing length to a threshold size or whether timing of fledging was delayed by younger age at peak mass or lighter peak body mass. Our results indicate that younger chicks remained in their nests longer than older chicks at the beginning of pre-fledging mass recession, regardless of the small variation in wing length among individuals. Annual variation in the duration of mass recession was also detected but body mass was not the trigger for fledging. Measurement of baseline corticosterone level indicated a negative trend between the corticosterone level and the number of days between the measurement date and the fledging date.
The status of the two taxa of Pericrocotus minivets recorded in northeast Asia (divaricatus and tegimae) is controversial, with some authorities considering them subspecies but most considering them full species. Therefore, in order to further understand the status of these taxa and to elucidate geographic patterns of morphometric variation in their populations, I examined 85 museum specimens collected from Japan and neighbouring territories. The results confirm that morphometric differences exist between the two taxa, the northern migratory divaricatus and the southern sedentary tegimae, and that these differences are statistically significant. However, the results also reveal that there is considerable geographic variation, in terms of wing length, between populations within each taxon. In particular, the population of tegimae resident in Kyushu, Japan, has significantly longer wings than populations further south in the Nansei Shoto; and populations of divaricatus from the Korean Peninsula and adjacent regions have smaller beaks and shorter wings than the population in Honshu, Japan.
To determine the major factor of change in provisioning rates to Varied Tit Parus varius nestlings in relation to increasing elevation, we used video recordings to investigate the number of parent visits and the size of prey carried by parents to their nestlings during the breeding process. Video cameras were installed at the entrances of 35 nests (17 at 300 m a.s.l., 7 at 900 m a.s.l., and 11 at 1,400 m a.s.l.). We also measured air temperature during the breeding season at three study sites. The provisioning rates per nestling showed a significantly negative relationship with prey size provisioned, except during the early nestling stage (days 1 to 4), when small prey were selectively provisioned by the parents. Prey at the higher elevation during days 5 to 15, also, were significantly smaller than at the lower elevation. The mean temperature at each breeding site during the breeding period did not differ significantly due to the delayed onset of breeding at higher elevation. Therefore, we conclude that the increase in the provisioning rate per Varied Tit nestling at higher elevation is associated with a decrease in prey sizes at that elevation, rather than with a difference in the temperature.
Japan hosts more than 40% population of Brent Goose Branta bernicla wintering in East Asia. We used satellite-tracking technology to monitor the seasonal movements and habitat usage of Brent Goose wintering in northern Japan. We marked five geese on the Oya sandy beach, Miyagi Prefecture, northeast Honshu, on 21 January 2014. The geese utilized areas along the seacoast, especially concentrating at a small bay, close to the capture site. Most of the geese offshore were found at fishery rafts. No geese were found more than 2 km offshore or more than 6 km from the capture site along the seacoast. In early April, the geese left the southern Sanriku coast and moved up to eastern Hokkaido, crossing the sea directly or via the coastal areas of Iwate and Aomori Prefectures. The geese predominantly remained in the vicinity of the Veslovskiy Peninsula, Kunashiri (Kunashir) Island, while some were distributed along the northern coast of the Nemuro Peninsula. We identified eastern Hokkaido and Kunashiri Island as important stopover sites for Brent Goose wintering in Japan.
The Japanese Murrelet Synthliboramphus wumizusume is listed as a vulnerable species by IUCN, but little information is available on its movements during the non-breeding season. We tracked three murrelets during the non-breeding season using light-level geolocators in 2012-2014. Birds from Eboshijima in Kyushu and Koujima in Shikoku were each tracked for one year, and one bird from Birojima in Kyusyu was tracked for two years. All three moved northward in the Pacific Ocean off Shikoku and Honshu in the spring then to the Pacific and the Sea of Japan off Hokkaido and off Sakhalin. In the fall and early winter two movement patterns were observed: (1) southwestward along the coast of Primorskii, the People's Democratic Republic of Korea, and the Republic of Korea; (2) southwestward movement along the east and south coasts of Honshu and Shikoku. In winter, two stayed in the southwestern part of the Sea of Japan, while the third moved southward into the Pacific Ocean.
The diets of the Intermediate Egret Egretta intermedia, Little Egret E. garzetta, and Cattle Egret Bubulcus ibis were examined by analyzing nestling regurgitations collected during the breeding season in 2005 at a colony in Asan, South Korea. Intermediate Egret nestlings mainly fed on insects (86.7% of total prey items), but fish were the most important group by biomass (64.3% of total biomass). Little Egret nestlings fed mainly on insects and fishes (43.4% and 33.2% of total items, respectively), and fish contributed 64.2% to the total biomass consumed. Cattle Egret chicks were mainly fed invertebrate prey (96.5% of total items), such as insects and spiders, which comprised just 64.3% of the total biomass of their diet. Loaches and aquatic insect larvae (mainly Odonata and Coleoptera) comprised a large proportion of the nestling diet of the three egret species. This suggests that all species forage primarily in rice fields, which represented the most extensive habitat surrounding the breeding colony.
Chestnut-cheeked Starlings are summer visitors that breed in central and northern Japan and then pass the winter in Southeast Asia. Their breeding ecology has been intensively studied, and the effect of climate change on the breeding season has been shown. However, it is not yet known to what extent stopover and wintering conditions influence the advance of their breeding season because the migration areas and migration timing are not well known. In order to obtain such basic migration information, we attached light-level geolocators to Chestnut-cheeked Starlings breeding in Niigata, central Japan. The starlings started their autumn migration in September and after staying in Kyushu for eight days or more, they migrated through the Nansei Islands to the Sakishima Islands, then Taiwan, or Fujian (China) in a relatively short period of time. They arrived on their wintering grounds by late October. Their migration period averaged 33.9±8.3 days. Seven (44%) out of the 16 individuals that we tracked wintered in the central and southern Philippines and nine (56%) on Borneo. They remained in their wintering areas for an average of 166.3±5.9 days before commencing spring migration during late March. After staying for a period of time on Luzon Island in the Philippines and then traveling northwards through the Nansei Islands of Japan, they headed for their breeding grounds in Niigata arriving back there between 10-26 April, after an average of 27.0±5.6 days.
We investigated avian frugivory during bird visits to fruiting Prunus verecunda and Swida controversa trees in Ogawa Forest Reserve, Japan, to: (1) quantitatively determine rates of frugivory by each species in a cool temperate forest, and (2) identify how three factors (location at forest edge or interior, crown area, and quantity of mature fruits) affect frugivory. We identified potential frugivores by means of bird fauna censuses and directly observed the frequency of visits to trees (FVT) and the number of fruits removed per visit (NFR) from 15 P. verecunda and six S. controversa trees. Based on our censuses, 18 bird species were predicted to visit P. verecunda during its fruiting period; however, 10 species actually visited, and only four removed fruits. Whereas we predicted that 22 species would visit fruiting S. controversa, 13 species actually visited, and only eight removed fruits. FVT and NFR differed significantly among bird species, and the potential number of fruits removed per hour differed among bird species and between tree species. Different factors affected FVT and NFR and also differed between tree species, probably because of seasonal changes in bird behavior. This study suggests that direct observation is useful for calculating how frugivory differs quantitatively among avian or tree species.
Breeding population abundance such as colony size of seabirds is not generally considered to be particularly sensitive to the annual dynamics of the food conditions because of the long life-span and high adult survival rate. However, in seabird species in which adults decide to breed or not depending on the food conditions, population abundance can respond sensitively to the annual variation in the food conditions. Here, we examine the effects of the regional annual stock abundance of Japanese Sand Lance Ammodytes personatus, and their local temporal availability during the egg-laying period on the size of a Black-tailed Gull Larus crassirostris and Slaty-backed Gull L. schistisagus, breeding colony over 12 years on Rishiri Island, northern Japan. The total number of nests of both gull species increased significantly with the regional annual stock abundance, but not with the local temporal availability of the sand lance. The number of Black-tailed Gull nests without eggs was significantly higher in the year with lower local temporal availability indicating that more Black-tailed Gull parents gave up egg-laying after nest building. Colony size in these species can be a useful indicator reflecting local food conditions.
We observed three Sand Martin Riparia riparia repeatedly attempting to copulate with a dead bird lying face down on the ground, with its wings spread and lowered. One of the three remained on the ground close to the dead bird and guarded it against copulation from the other two birds. Then, the guarding bird itself attempted to copulate with the dead bird. Based on subsequent dissection the dead Sand Martin was identified as an adult male. Based on our observations, we propose that the observed homosexual necrophilia may be partly explained by the absence of sexual dimorphism in this species and the posture of the dead martin. We suggest that posture is an important trigger arousing male sex drive in a sexually monomorphic species.