Bird Research News

Vol.8 No.5

2011.5.27.

Rufous Hawk-Cuckoo

Ju-ichi (Jpn) Hierococcyx hyperythrus

Morphology and classification
Classification: Cuculiformes Cuculidae
The classification of the Rufous HawkCuckoo has been established recently.
They are included in genus Cuculus
along with Common (Cuculus canorus)
and Lesser Cuckoos (C. poliocephalus) inmany classification system, but they areclassified as Hierococcyx hyperythrus in
the latest classification system of Cuculiformes (Payne 2005). Genus Hierococcyx is a sister group of genus Cuculus interms of molecular phylogeny and includes the Large Hawk-Cuckoo (H. sparverioides) and the Common HawkCuckoo (H. varius) which are distributed Photo 1. Adult Rufous
in South and Southeast Asia. The two
Hawk-Cuckoo. [Hiroshispecies are usually classified under genus
Uchida]Cuculus along with the Rufous HawkCuckoo, but they are especially similar to hawks as the English nameof "hawk-cuckoo" implies and different in call from genus Cuculus.

Breeding system:
Rufous Hawk-Cuckoos are obligate brood parasites. They primarily
parasitize Blue-and-white Flycatchers (Cyanoptila cyanomelana),Siberian Blue Robins (Luscinia cyane) and Red-flanked Bluetails(Tarsiger cyanurus), without raising own young (Higuchi 1998).
There is no detailed information about the mating system, but they areprobably promiscuous as Common Cuckoos (Davies 2000).

Nest:
Rufous Hawk-Cuckoos do not build a nest. Instead, the host species
build a cup-shaped nest using moss (Blue-and-white Flycatchers),
leaves of a broad-leaved tree (Siberian Blue Robins) and needles andtwigs of a coniferous tree (Red-flanked Bluetails) in holes on a slope
or at the foot of a tree.

Egg:

Both male and female are charcoal gray on the upper part withwhite and orange bands on the tail. The throat is white, and thechest and belly are pale orange. The eye rings are bright yellow.
Non-adult birds have feathers with orange bands on the back. Theylook similar to a male Japanese Sparrowhawk.

Since Rufous Hawk-Cuckoos are brood parasites, females lay one egg
in each host's nest. It is unknown, however, how many eggs one female lays in a single breeding season, though it would be similar to thenumber of eggs a female Common Cuckoo lays in a breeding season,
about 25 eggs in total. Rufous Hawk-Cuckoos lay relatively large eggs
among all cuckoos. The size is 28.1mm by 19.9mm and the volume
amounts to 5.7ml (Higuchi 1998), while the egg size of the Common
Cuckoo is about 3.4ml in volume (Kruger & Davies 2004). Considering that Rufous Hawk-Cuckoos are roughly similar in weight to Common Cuckoos, the difference in egg volume between the two species issurprising. Eggs of Rufous Hawk-Cuckoos are usually pale blue or
bluish green, but some of them have light brown speckles. The eggs
are somewhat similar to those of the Siberian Blue Robin, which areturquoise blue, but they are quite different from those of the Blue-andwhite Flycatcher and the Red-flanked Bluetail, which have light brownspeckles on the white background. The egg coloration of parasitic
birds is generally similar to that of their hosts so that their eggs may
evade detection by hosts (Moksnes & Roskaft 1995). It is not clear
why Rufous Hawk-Cuckoos have not evolved elaborate mimicry ineggs.

Vocalization:

Incubation and nestling periods:

Males shriek "Joo-ichi, Joo-ichi" with an accent on the secondsyllable. They occasionally babble "Jubi-jubi-jubi" when in a dispute with each other. Females also make this sound.

The eggs that Rufous Hawk-Cuckoos lay in the nest of Red-flanked
Bluetails hatch about 13 days after laying, as parasitic cuckoo chicks
need to hatch earlier than their hosts to remove the eggs of their hosts
from the nest. The incubation period of the Rufous Hawk-Cuckoo isshorter than that of the Red-flanked Bluetail whose eggs hatch inabout 14 days. Common Cuckoo eggs hatch about 12 days of incubation (Davies 2000). Rufous Hawk-Cuckoo chicks that are raised by
Red-flanked Bluetail host parents fledge about 18 days after hatching.
The nestling period of Rufous Hawk-Cuckoos is longer than that of
their host chicks, which fledge in from 11 to 14 days, but is similar tothat of Common Cuckoos. There is no detailed information about theeggs laid in Blue-and-white Flycatcher and Siberian Blue Robin nests.

Total length:
Tail length:
Tarsus length:305-330 mm
135-145 mm
22-24 mmWing length: 180-210 mm
Culmen length: 20-23 mm
Weight:99.0-147.8g

The measurements are after Enomoto (1941).

Appearance:

Distribution and Habitat
Distribution:
Rufous Hawk-Cuckoos visit as a summer resident in Japan (northof Kyushu), South Korea and the Amur River valley, China andRussia to breed, but there is no detailed information about theirrange north of Siberia. They winter in the tropic and subtropic
forests of Southeast Asia (Payne 2005).

Habitat:
In Japan they breed in forests from low mountains to a subalpine
zone in the southern part of Honshu (the largest island of Japan).
They breed in forests of the lowlands in high latitudes. Since theydepend entirely on their host species for their breeding, they usually occur in forests along a mountain stream where their hosts prefer to build a nest. Since the three host species which I will describe later are sympatric or parapatric, and generally occupy different areas of the same river system according to altitude, it isassumed that Rufous Hawk-Cuckoos can efficiently parasitizethese species by moving along a stream.

Life history1234

wintering period

5678910breeding migration

11 12wintering

Migration:
Rufous Hawk-Cuckoos winter in tropical and subtropical regions inSoutheast Asia, and migrate to the breeding grounds in Japan, Korea,
Northern China and Siberia as a summer resident. They first arrive in
Honshu (the main island of Japan) in early May and lay eggs from mid-May to early August according to their host's breeding seasons. They
are assumed to leave the breeding grounds for wintering around October.

Topics of ecology, behavior and conservation● Adult birds
Rufous Hawk-Cuckoos sing and call so loudly that you can hearthem very well from a distance, but they are rarely observed because
they are extremely cautious. You would need the luck of the devil tosee them hiding in the dense leaves of a tree canopy, when you are
guided by their songs and calls to them. Therefore, there is little orno detailed information on their ecology.

4♪ http://www.bird-research.jp/1_shiryo/koe/juichi_090527_shioya_hirano .mp3
Toshiaki Hirano♪ http://www.bird-research.jp/1_shiryo/koe/juuichi_0805_hyogo_kaji.mp3
Kyoko Kajimoto

Bird Research News

Vol.8 No.5

2011.5.27.

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

Photo 2. A Rufous Hawk-Cuckoo nestling and the mouth of a Red-flanked
Bluetail nestling (left). A Rufous Hawk-Cuckoo nestling displaying thewing patches towards a Red-flanked Bluetail host that came to feed it(right).

Feeding frequency per hour

Hawk-cuckoo nestlings show this behavior more frequently when
they are hungry (Tanaka & Ueda 2005). At the least they might use
the yellow patches as a signal to solicit food. We carried out anexperiment to examine how the hosts reacted to experimental manipulations on the yellow patch of Rufous Hawk-Cuckoo nestlings.
The provisioning rates were significantly reduced to the nestlings in
a condition that their patches were painted black (the experimentalgroup) compared to those in conditions which nestlings did notreceive manipulations (control group I) and which their patches
were painted a transparent solvent (control group II) (Fig. 1: Tanaka& Ueda 2005). The study showed that the yellow wing patches of
Rufous Hawk-Cuckoo nestlings have the function of stimulating
their hosts to feed more food to them. The hosts were occasionallyobserved to try to place food into the yellow wing patches, mistaking them for the mouth of the nestlings (Tanaka et al. 2005). Like
Common Cuckoos, Rufous Hawk-Cuckoo nestlings also put theeggs and chicks of the hosts
35
on their back and eject
30
them from the nest a little
25
after they hatch to monopo20
lize the nest. Therefore, thehosts which try to feed the15yellow patches can mistake10
them for the mouths of5
their own chicks. The yel0
low patches probably makeControl
Control Manipulated
an illusion in host parents’group I
group IIgroupmind that there are several
Fig. 1. The feeding frequency decreased
chicks in the nest. It issignificantly only in the manipulated
reasonable to assume thatgroup where the wing patches were
this illusion is responsible
painted black. Modified from Tanaka& Ueda (2005).
for the increased provisioning.

● Colors the host species perceive as a signal
The color of the skin of Rufous Hawk-Cuckoo chicks is bright yellow to us, but it is now widely known that birds have a different
vision than we humans have. My colleagues and I measured thereflectance spectrum of light in the visible range of birds (300700nm) with a spectrophotometer and compared the mouth color ofreflectance and proportion of light
captured by photoreceptors
0.20.40.60.8It is not easy to study the nestlings as well, not only because thenests of their hosts are cryptic and thus they are difficult to spot but
also because the parasitism frequency is usually not so high. For
instance, only 9% of Red-flanked Bluetail nests are parasitized in ayear on average. Despite that, the nestlings of the Rufous HawkCuckoo have highly unusual features as follows.
The nestlings have a bright yellow skin not only in the mouth but
also on the underpart of the wings where the bare skin is exposed
partially. (Photo 2. Left). Moreover, when host parents bring food tothe nest, the nestlings raise and shake their wings to show off theyellow patches (Photo. 2. Right).

Rufous Hawk-Cuckoo patch
Red-flanked Bluetail nestRufous Hawk-Cuckoo mouthlings to those of the hawkRed-flanked Bluetail mouth
cuckoo chicks’ mouth andthe wing-patch, in reference to the assumed visualperformance of the adultRed-flanked Bluetails, byaccounting the sensitivityof photoreceptor cells
300400500600700
wavelength (nm)(single-cones) on birds’
retina. The result showed Fig. 2. Dotted lines show reflected spectraand solid lines show portions that thethat the colors of theretinal cones of the host species canmouth and the wing patchreceive, which are called photon capes of Rufous Hawkture and constitute perceived colors.
Cuckoo nestlings reflected
The reflectance spectra of the Rufous
both UV and yellow much
Hawk-Cuckoo are especially higher inmore strongly than thethe ultraviolet range (< 400nm) thanmouth color of Redthat of the Red-flanked Bluetailflanked Bluetail nestlings,chicks.
suggesting that the color of
the mouth and the wing-patch of the hawk-cuckoo would be considerably different from the mouth color of bluetail chicks (Fig. 2). In
general, mouth colors of chicks function as an important foodsolicitation signal to parents. Since Rufous Hawk-Cuckoo nestlings
are larger in size and need a greater amount of food, it is assumed
that the strong coloration of the Rufous Hawk-Cuckoo chicks might
have evolved as a "supernormal stimulus (the pattern of a stimulus
which is more effective than stimuli found in normal conditions:
Yamagishi et al. 2004)" to urge their host parents to feed a larger
amount of food to their nestlings (Tanaka in print, Tanaka et al. inpress).

0.0● Nestlings

バードリサーチ生態図鑑

Literature
Davies N.B. 2000. Cuckoos, Cowbirds and other Cheats. T&AD Poyser, London.
Enomoto Y. 1941. Body size of Japanese Birds. Osaka Chapter of Wild-Bird Society of Japan, Osaka. [J]Higuchi H. 1998. Host use and egg color of Japanese cuckoos. In Parasitic Birdsand Their Hosts: Studies in Coevolution (eds. Rothstein S. I. & Robinson S. K.),
pp 80-93, Oxford University Press, Oxford.
Moksnes A. & Roskaft E. 1995. Egg-morphs and host preference in the common
cuckoo (Cuculus canorus): an analysis of cuckoo and host eggs from European
museum collections. J. Zool. 236: 625-648
Payne R.B. 2005. The Cuckoos. Oxford University Press, Oxford.
Tanaka K.D. & Ueda K. 2005. Horsfield’s hawk-cuckoo nestlings simulate multiple gapes for begging. Science 308:653
Tanaka K.D., Morimoto G. & Ueda K. 2005. Yellow wing-patch of a nestling
Horsfield's hawk cuckoo Cuculus fugax induces miscognition by hosts: mimicking a gape? J. Avian Biol. 36:97-101
Tanaka K.D., Morimoto G., Stevens M. & Ueda K. in press. Rethinking visualsupernormal stimuli in cuckoos: visual modeling of host and parasite signals.
Behav. Ecol.
Tanaka K.D. In print. Satan's child that manipulates color: nestlings of a broodparasite bird the Rufous Hawk-Cuckoo- communications that use color in birdsand exploitation by parasite - In "Species biology research Vol. 36 the worldthrough the eyes of animals (Makino T. & Yasumoto, A. eds.)", Chapter 4, Bunichi Sogo Pub. Tokyo. [J]Yamagishi S., Morioka H. & Higuchi H. 2004. Dictionary of Ornithology. Shoa-doPub. Kyoto. [J]Languages of literature cited other than English: [J] in Japanese, [J+E] in Japanesewith English summary.

AuthorKeita TANAKA Department of Science at Rikkyo University
I am interested in the behavior and evolution ofanimals and engaged in the study of this field. Presently "colors through the eyes of birds" is my major
theme. I would like to continue to study other birds
and animals as well as Common Cuckoos and Rufous Hawk-Cuckoos.
keita.d.tanaka@gmail.com

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