Bird Research News

Vol.4 No.6

Long-billed Plover

2007.6.15.

Ikaru-chidori (Jpn) Charadrius placidus

Morphology and classification

Life history
12Classification: Charadriiformes Charadriidae
Total length:
207mm (197-222)
Wing length: ♂ 142.6±3.5mm (N=32) ♀ 144.2±3.2mm (40)
Tail length:♂ 77.6±3.3mm (32)
♀ 77.6±3.8mm (40)
Culmen length: ♂ 19.5±0.8mm (32)
♀ 19.8±0.8mm (40)
Tarsus length: ♂ 32.4±1.3mm (32)
♀ 32.5±1.3mm (40)Weight:♂ 63.6±3.3g (32)
♀ 68.1±4.2g (40)
Hatchling: Weight 8.5±0.6mm (30), Tarsus length 22.1±0.6mm (18),Culmen length 9.2±0.4mm (18), and Total length 65.9±2.5mm (18).
Total length is after Enomoto (1941), and the other measurements are the mean valuesin Tokigawa in Saitama Prefecture in the incubation period. For the hatchlings themean values on the day of hatching.

Appearance:

90

Weight (g)Males and females are similar inFemale
plumage coloration. They are80
Malegrayish brown on the back and70
white on the belly. They haveblack bands on the head and60
breast. The iris is dark brown and50the eye is ringed with yellow bareskin, which is paler and less con40
130
135
140
145
150155
spicuous than that of Little
Natural wing length (mm)Ringed Plovers (Charadrius dubius). In the breeding plumage Fig. 1. Relationship between the(summer plumage), however,natural wing length and weight
there are some differences beof Long-billed Plovers.
tween the sexes. The feathersaround the eye become darker inmales than in females. The blackband on the forehead is also wider in males than in females. In thenon-breeding plumage (winterplumage), on the other hand, buff
-colored feathers increase on theface in both sexes, but it is difficult to distinguish a male from afemale, though there is a slightdifference between them. They Photo 1. Long-billed Plover male
molt completely into the nonin summer plumage.
breeding plumage from July toAugust, while they molt partially into the breeding plumage from
November to January.

Vocalization:
Long-billed Plovers fly flapping their wings vigorously and uttering a
staccato call which sounds like "Fi, fi, fi, fi, fi" in the breeding period.
Males sometimes call like "Gee, gee" quietly, thrusting the chest as
well. When on the alert, they make a single call that sounds like"Pyuoo- !", but they call like "Pip-pip-pip", when they take shelter.

Distribution and Habitat
Distribution:
Long-billed Plovers are distributed in Japan and the Chinese Continent. They are mostly a year-round resident in Honshu, Shikokuand Kyushu (the main islands of Japan), but they leave Hokkaido(the northernmost main island of Japan) for temperate regions inwinter. They are breeders in the north-central China and winterresidents in southern China through Myanmar.

3 4 5 6breeding season

78 9 10 11 12
non-breeding season

Breeding system:
Long-billed Ringed Plovers are basically monogamous and pairs holdtheir territory. Male and female share the incubation of their eggs andnestlings alike at the early stage of breeding. If they raise their young
successfully half through the nestling period, however, females sometimes leave their nestlings in the care of their partner and attempt tobreed again with another male (successive polyandry). If they frequently fail in their breeding attempts, females usually divorce theirpartner and leave the territory, but males rarely abandon the territory.

Breeding behavior:
The breeding behavior is observed from late February. The malepresses the chest against the ground to dig a shallow hole raking out
the gravel by the feet and call for the female from the hole. When thefemale comes, the male stands up and opens the tail to make a courtship display with the open tail. The female enters the hole under thetail of the male. The male digs many holes at this time and puts on adisplay to lead the female to them. The female lays eggs in one ofthem.

Nest and egg:
The nest hole of Long-billed Plovers
is about 13cm in diameter and about
4cm in depth dug into the gravel
ground by the male. They occasionally nest in the arable land adjacent to ariver. They use as nest materials pebbles with a diameter of less than 1cm
in diameter and 1-3cm dry grass
Photo 2. Nest and eggs ofstalks.
Long-billed Plovers.
The clutch size is mostly four eggs.
The egg size is 34.8 ± 1.3mm (30.7-38.6mm, 512) by 28.2 ± 0.7mm(23.1-28.2mm, 512). The egg weighs 11.8 ± 0.9 g (8.7-14.2g, 512).
The egg has brown or dark brown flecks all over, but more densely
around the blunt end, on a bluish gray or grayish brown ground.

Incubation and nestling periods and fledging rate:
They lay one egg every other day and it takes about seven days tocomplete the clutch. Four eggs hatch about 29 days on average after
the incubation started, but the incubation period somewhat varies due
to frequent human disturbance. When enemies approach the nest
during the incubation, the parent birds leave the nest quietly andwatch over the nest in the distance. When enemies approach the nestat the time of hatching, the parent birds move toward them and feign
injury while calling loudly. The hatchlings leave the nest several
hours after hatching and start feeding by themselves, while watchedover by the parents. The young increase in weight by about 1g per day
and they come to fly at the age of about 40 days. Then they dispersefrom the parents' territory. In the study site only about 15% of the laid
eggs hatched and less than half of it survived due to predation oraccidents. When they failed in breeding, they laid eggs again in about
seven days.

Territory:

Long-billed Plovers usually occur in the gravel ground with little
or no vegetation in the middle reaches of a river valley. In winter,however, they are also found in paddy fields and themuddy ground of a river.

Long-billed Plovers have monogamous breeding system and pairs
maintain their territory. They establish a territory on the bareground such as gravel, but not on a dry riverbed covered with vegetation. The territory generally extends about 100m along a river.
They actively carry out a territorial display, flying around the territory in the air many times while calling. The boundary between theterritories on the ground is distinctly demarcated and territory
owners frequently run parallel to each other along the boundary,threatening with their chest thrusted early in the breeding season.
They occasionally jump up and peck at each other viciously in aterritorial dispute. Females also take part in a territorial dispute.

♪ http://www.bird-research.jp/1_shiryo/koe/ikaruchidori_100427_utsunomiya.mp3♪ http://www.bird-research.jp/1_shiryo/koe/ikaruchidori_130618_nasushiobara_hirano.mp3

Habitat:2
4

Toshiaki Hirano

Toshiaki Hirano

Bird Research News

Vol.4 No.6

2007.6.15.

© Japan Bird Research Association
Sumiyoshi 1-29-9, Fuchu, Tokyo, Japan

Diet and foraging behavior
Long-billed Plovers forage for prey at the shoreline of a river, andwhen they catch sight of prey, they suddenly move toward it andcatch it. Although it is rare that the prey species is confirmed, theyare assumed to capture small insects in the water. I observed themcapture imagoes of midges that fell at the edge of the water, aquatic insects, adult dragonflies, larvae of beetles and earthworms, etc.,
but they ingest no vegetable matter.

Topics of ecology, behavior and conservation● RoostThe male and female roost together in their territory during thebreeding season. In July when the breeding period is over, however, Long-billed Plovers form a colonial roost in a flock of several
to three dozen birds from the morning to the evening in a dry riverbed or the arable land with bare areas adjacent to a river. A
roosting flock consists primarily of birds within a range of about
1km of the roost site. In the study site, for instance, a roosting
flock was composed half of breeders and half of immigrants.

● Seasonal changes of behavior
Long-billed Plovers are diurnal during the breeding period whichstarts in February. They leave their roost to feed at dawn and return to their roost at dusk. When the breeding season is over inJuly, on the other hand, they form a communal roost in the daytime and they return to a river at dusk to forage along the shoreline. Around December, however, they keep irregular hours. Somebirds sleep and others forage in the daytime.

バードリサーチ生態図鑑
At that time, however, BF♀ (his wife) came running from a distance and attacked the young female that was accepting the courtship from BF♂, as if to say "What the hell are you doing in myplace!". (Please pardon such a personification.) The female stoodup and ran away a short distance. Then, BF♂ changed his attitude
completely toward the female that had accepted his courtship up tothen, and rushed to peck at her, as if to say "Boy, you are not mywife!". The female gave out a scream and flew away to the waterside. BF♂ stood for a moment, looking embarrassed. After BF♀
walked away, however, BF♂ started to invite the young female tothe hole with a courtship call again. Then, the female came running back to him and squatted under his tail, accepting his courtship again. Soon BF♀ arrived again. Seeing his wife, BF♂ stopped
courting at once and started to peck and chase away the female
from under the tail. The female flew away screaming, but the malechased after her obstinately to drive her out of the territory. WhenBF♂ returned to his wife as if nothing unusual had happened, shewalked away from him again. Left alone, BF♂ looked somewhat
crestfallen.
Now let us think about the reasons behind this male's behavior.
When Long-billed Plovers fail in their breeding attempt, the females sometimes divorce their partner and leave the territory, butthe males usually remain in the territory. Since the males are always at risk of being divorced, they seem to be tolerant toward
intruding females.
I consider that this behavior reflects the "psychology of Longbilled Plover males”. What do you think of it ?
The author has not published this study in a form of a monograph.
It is the result of the study he carried out for seven years from1987 to 1994 in the Tokigawa River, Saitama Prefecture, central
Japan.

Literature● Dispersal and establishment of juveniles
Three males and four females were confirmed to settle down in mystudy site. One of the males established its territory the next yearand started breeding. Another male returned to the study site andattempted to breed two years later, but it failed and left the studysite again. The third male bred in a riverbed a dozen kilometers
away from the study site the following year. Four females attempted to breed the year after they had fledged. But they failed several
times and left the study site except for one female, which remained
there for as long as 14 years. The study showed that males andfemales sometimes stayed in the vicinity of the natal site and thatthey started to breed the year after they had fledged.

● Psychology of Long-billed Plover males
It is relatively easy to observe most of their daily life except for in
the nighttime because Long-billed Plovers hold their territory in anopen habitat. The private life of banded birds can be exposed.
During my seven-year study of Long-billed Plovers, I observed
many interesting episodes, among which I would like to introducea very amusing one I observed only once.
There was a pair I named BF in the study site. I captured and banded the male (BF♂) and female (BF♀) of this pair in 1988. They
maintained their pair-bond until the male (BF♂) disappeared threeyears later. They failed in the first breeding attempt in 1989, but I
observed BF♂ uttering a courtship call from a hole he had dug inthe riverbed of the territory in May of the same year. There appeared a ♀ without a color leg band in response to his call. Speeding up the tempo of the call, BF♂ stood up and opened the tail to
invite her. The female accepted his courtship and squatted down in
the hole.

Hirai M. 1999. Nesting of Long-billed Plover Charadrius placidus in Mie prefecture. Strix 17 77-83. [J+E]
Taylor R.C. 1979. Moult of the Long-billed Ringed Plover Charadrius placidus.
Bull. B.O.C.
Kiyosu Y. 1978. Great Reference of Japanese Birds II. Revised edition with supplement. 674-675. Kodansha. Tokyo. [J]Nakamura T., & Nakamura M. 1995. Illustrated Book on the Ecology of JapaneseBirds. 99-100. Hoikusha, Osaka. [J]Takano S. 1982. Field Guide to the Wild Birds of Japan. Wild-Bird Society ofJapan. Tokyo. [J]Languages of literature cited other than English: [J] in Japanese, [J+E] in Japanesewith English summary.

AuthorHiroshi UCHIDA Resident of Higashimatsuyama City, Saitama
Since I find it too much trouble to go to distant sites, I make it a rule tolook for research topics in the vicinity of my house. It takes just about
15 minutes to drive to the study site of Long-billed Plovers from myhouse. Incidentally, the study sites of Cuckoos, Goshawks and Little
Cuckoos are 45, 20 and 20 minutes away bycar, respectively. When I study a target birdspecies for several years and I have got ageneral idea of it, I tend to think I have fully
understood it and lose interest and startworking on another species. Since I go from
one theme to another with leaving collected
data alone, I have hardly ever publishedscientific papers. It is a bad habit of mine as
an amateur ornithologist. I regret it.
tori@po.kumagaya.or.jp

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