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Breeding Records of Little Egret Egretta garzetta in Sumatra, with notes on the occurence of race E. g. garzetta

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Abstract

Terdapat enam subspesies Kuntul Kecil Egretta garzetta. Satu dari enam subspecies tersebut yaitu subspesies nigripes ditemukan tersebar luas di Sumatera, tanpa ada ada catatan berbiak. Survei yang dilakukan pada tahun 2008 mengkonfirmasi bahwa Kuntul Kecil berbiak di Sumatera, dan juga menemukan bahwa subspesies lainnya yaitu garzetta juga ditemukan di sepanjang pesisir timur Sumatera.
Kukila 16 (1) 2012 Short Communications 59
First Confirmed Breeding Records of Little Egret
Egretta garzetta in Sumatra, with notes on the
occurrence of race E. g. garzetta
MUHAMMAD IQBAL1, AGUS NURZA2 AND GIYANTO3
1KPB-SOS, Jalan Tanjung api-api km 9 Komplek P & K Blok E 1 Palembang 30152,
Sumatera Selatan, Indonesia. Email: kpbsos26@yahoo.com; 2Cicem Nangroe, Jl. Hasan Dek
No. 78 B (Menys Flower) Simpang Surabaya, Banda Aceh, Indonesia; 3Jl. Bunga Wijaya no.
66, Padang Bulan Selayang, Medan 20131, Sumatera Utara, Indonesia.
Ringkasan: Terdapat enam subspesies Kuntul Kecil Egretta garzetta. Satu dari
enam subspecies tersebut yaitu subspesies nigripes ditemukan tersebar luas di
Sumatera, tanpa ada ada catatan berbiak. Survei yang dilakukan pada tahun 2008
mengkonfirmasi bahwa Kuntul Kecil berbiak di Sumatera, dan juga menemukan
bahwa subspesies lainnya yaitu garzetta juga ditemukan di sepanjang pesisir timur
Sumatera.
Introduction
The Little Egret Egretta garzetta occurs over much of the Old World from Europe
and Africa through India to Australia and New Zealand, (Hancock & Kushlan 1984).
Six subspecies are recognized, the most widespread of which is E. g. garzetta, found
from Europe to East and South-east Asia. Eastern populations of this yellow-footed
race are known to breed in southern China, Taiwan, South Korea and Japan,
Vietnam and migrate to South-east Asia and Philippines (Hancock & Kushlan 1984;
Robson 2008; Davidson 2009). Although a common non-breeding visitor to the
Thai-Malay Peninsula and Singapore from September to May (Wells 1999; Keng &
Hails 2007), it was not known to breed in Peninsular Malaysia until 2002; since then
breeding of garzetta has been discovered at four heronries, three of which were well
known (Shepherd 2007). The race nigripes, distinguished by its black feet, occurs in
the Indonesian archipelago and islands of the south-west Pacific (Hancock &
Kushlan 1984). This race breeds on Pulau Dua and Pulau Rambut, West Java
(Milton & Marhadi 1985; Mardiastuti 2002) and Bali, as well as in Borneo and
Sulawesi (Mann 2008; Myers 2009).
In Sumatra, the Little Egret has formerly been regarded as a non-breeding
visitor (Marle & Voous 1988; MacKinnon & Phillips 1993), though it has been
suspected of breeding on the island (Holmes & Noor 1995; Holmes 1996). Although
the only subspecies that has been confirmed from Sumatra is nigripes (Marle &
Voous 1988; Holmes 1996), MacKinnon & Phillips (1993) claimed that garzetta
was the most common race here, and in Borneo. Here, we present the results of
recent surveys which confirm that the subspecies garzetta occurs widely in Sumatra,
and that both subspecies breed on the island.
Methods
From January 2008 to January 2009, we conducted systematic searched for breeding
colonies of the Little Egret and other waterbirds along the east coast of Sumatra, in
three major provinces: Aceh (conducted by AN & MI), North Sumatra (from Bagan
60 Short Communications Kukila 16 (1) 2012
60
Percut in the north to Tanjung Balai in the south; GI & MI) and South Sumatra (MI).
Maps were used to locate potential study areas.
In each study area, we initially interviewed local people to determine the
location of breeding colonies. A standard set of questions was asked and answers
were recorded on an interview form. Preliminary questions assessed the
interviewee’s knowledge of waterbirds. Complete interviews were conducted only
with people having obvious knowledge of the species. This information was used to
target searches for breeding colonies. Routes and transport to identified sites were
organised with the assistance of local people. Coastal sites in Aceh and North
Sumatra were accessed using vehicular transport (car and motorcycles) or by foot,
and a small boat or canoe was used for crossing creeks. In South Sumatra, all sites
were accessed by boat. At breeding colonies, we counted the number of each species
of heron, and took note of the colour of the feet of all Little Egrets observed, as this
is the only reliable means of separating the two likely races (nigripes and garzetta).
Results
Three confirmed breeding sites were found during this survey: two in Aceh and the
other in South Sumatra.
Aceh Province
On 31 December 2008, site 1, located near SMAN 2 (Senior High School 2),
Lhokseumawe (5°10’36”N; 97°09’13”E), contained at least 35 occupied nests of
Little Egrets, of which up to 20 were garzetta (Plate 1) and at least ten were
nigripes. We did not see any evidence of hybridisation between the two races, or of
pairs comprising an individual of each race. On the same day, we saw up to 100
nests of the species at site 2 (5°07’53”N; 97°09’19”E), c. 10 km from site 1. We
could not determine the subspecies present at this rookery as it was too distant (c.
0.5-1.0 km) from the nearest point of access.
North Sumatra
On 4 January 2008 we observed a breeding colony of three species of egrets in
mangrove forest at Percut Sei Tuan (3°42’53”N; 98°46’46”E). Although Great
Egrets Ardea alba and Intermediate Egrets E. intermedia were observed standing on
nests, and Little Egrets were present, none of the latter were seen on nests. Due to
the deep mud and tidal water in front of the nesting trees, we were unable to inspect
the colony at close range. Most of the Little Egrets observed in North Sumatra
during this survey belonged to race nigripes, but we have two sightings of garzetta
in the province. One involved two birds seen in Karang Gading Langkat Timur
Nature Reserve (4°07’07” N; 98°21’27”E) on 2 January 2009 (Plate 2), and the
other, three birds from a total of 20 Little Egrets in Bagan Percut on 4 January.
South Sumatra Province
On 17 June 2008, a heronry including c. 300 egrets was found at Lake Kumpai
(2°26’02”S; 105°34’53”E), Tanjung Selokan (Selokan Bay), Ogan Komering Ilir
district, South Sumatra. Most were in breeding plumage. Three pairs of Little Egrets
were observed both standing and sitting at nests, but the nests’ contents could not be
seen. The subspecies was not identified because the birds were so distant from the
Kukila 16 (1) 2012 Short Communications 61
observers that it was impossible to obtain a clear view of their feet. The heronry was
located in an open mangrove backswamp of c. 15 ha, some 6-7 km from the coast,
with nests 2-10 m up in mangrove trees. When the area was visited, the area was
flooded to a depth of 10-30 cm. The mangrove trees supporting the nests were
identified as an Avicennia species. On 15 March 2008, a flock of c. 50 Little Egrets
was found near Sugihan Bay (2°24’49”S; 105°33’20”E). At first, it was suspected
that all of the birds were of the race nigripes, but a few birds had yellowish feet,
indicating they were race garzetta, and less than 10 birds had black feet with yellow
soles, as described for “occasional individuals” of nigripes (Kushlan & Hancock
2005). On 30 November 2008, there were two garzetta among a total of ten Little
Egrets observed at Sungai Lumpur, Ogan Komering Ilir.
Plate 1: A pair of Little Egrets E. g. nigripes
standing on their nest in a mangrove tree at
Lhokseumawe.
Plate 2: A Little Egret of race garzetta
foraging in Karang Gading Langkat Timur
Nature Reserve, North Sumatra.
Discussion
Marle & Voous (1988) reviewed the status of Little Egret in Sumatra, and concluded
that the species was a non-breeding visitor (nigripes) from Java. At Rawa (swamp)
Pacing on the Tulang Bawang River, North Lampung, possibly the largest heronries
in Sumatra, Holmes & Noor (1995) saw small numbers of Little Egrets in breeding
plumage entering the colony, which Holmes (1996) later reported as ‘suspected
breeding’. Our observations of nests in Lake Kumpai and Lhokseumawe confirm
that the Little Egret is now a breeding resident in Sumatra.
On Pulau Rambut, West Java, Little Egrets (nigripes) breed from early
December to the end of May (Mardiastuti 2002), while at Pulau Dua, also in West
Java, they breed for ten months of the year, starting in January or February (Y.R.
Noor, unpubl. data). Our observations of nesting at the end of December in Aceh,
and probable nesting in June in South Sumatra, therefore fall within the long
breeding season on the species. In Peninsular Malaysia, Shepherd (2007) reported
garzetta breeding in March and October, but did not define the breeding season.
AGUS NURZA
MUHAMMAD IQBAL
62 Short Communications Kukila 16 (1) 2012
62
Until now there have been no confirmed records of race garzetta in Sumatra.
Marle & Voous (1988) concluded that all Little Egrets in Sumatra belonged to the
race nigripes. During an intensive survey of the tidal lowlands and floodplains of
South Sumatra in 1988-1989, Verheugt et al. (1993) observed that all Little Egrets
had the black feet of the race nigripes. MacKinnon & Phillips (1993), on the on the
other hand, asserted that both the yellow-footed (garzetta) and black-footed
(nigripes) subspecies from mainland Asia and Java, respectively, visited Sumatra,
and that the former was the commoner of the two. In his review of the Sumatran
avifauna Holmes (1996) did not report race garzetta, although it was reported from
Kalimantan (Holmes 1997). Our observation of garzetta in Sugihan Bay on 15
March 2008 therefore constitutes the first confirmed record of this race in Sumatra.
Shepherd (2007) reported an expanding breeding range of garzetta in
Peninsular Malaysia as far south as Rawang, Selangor. We observed this race
breeding at Lhokseumawe, which extends its breeding range c. 600 km westwards
from Rawang. We were unable to identify the subspecies of all nesting Little Egrets
seen in Sumatra, but it is possible that nigripes is also expanding its breeding range
westwards from the north-west coast of Java (Pulau Dua and Pulau Rambut) to
Sumatra, especially given that Lake Kupai is only 250 km from Pulau Dua.
Acknowledgments
These observations were made during field work for a Milky Stork Mycteria cinerea
population assessment in South Sumatra, supported by Rufford Small Grant (RSG), WCS
RFP (Wildlife Conservation Society Research Felowship Programme) and Idea Wild. We
would like to thank Pak Ajit (formerly head of Sungai Batang village), Qodir and Pak Reli’s
family in Sungai Batang, South Sumatra province. We are also very grateful to Greg Baker
and Richard Noske who reviewing and improving our earlier draft.
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Article
This annotated checklist is the third major compilation for Singapore. It lists the current status of all bird species ever recorded in the wild in Singapore. A total of 404 species have been recorded, including 44 species which are now extinct or have not been recorded for the last 50 years. Some of the latter species have been recorded again as non-breeding visitors. There are now 342 species that occur naturally in Singapore and another 22 species that were introduced by man. Fifty-eight families of birds are represented. There are 121 resident species with proven breeding records and 21 other presumed residents. One hundred and fifty-four species are winter visitors and/or passage migrants, with another 25 species listed as non-breeding visitors and 21 others that occur in Singapore as vagrants. Census data since 1991 shows that the total number of birds in Singapore has declined by 40 % and the number of species has declined by nearly 17 %. The most abundant bird species Is a migrant, the Pacific Golden Plover (Pluvialis fulva). The most important site in terms of bird population is Sungei Mandai, an unprotected mudflat and mangrove ecosystem while Sungei Buloh Wetland Reserve and Pulau Ubin are important in having the highest diversities of birds. The loss of mudflats through reclamation, damming of estuaries, and canalisation of rivers has resulted in a decline in waterbird density and diversity as shown in the Annual Waterfowl Census. The current total shorebird population in Singapore is only 4,000 - 5,000 birds, a vast decrease from the large wintering population of 10,000 birds at a single site, the Serangoon Estuary, in 1985. Forty-one of the 44 extinct species were resident forest birds, of which, 34 (82.9 %) went extinct between 1900 and 1950. This equates to 3.4 species lost every five years, an alarming rate of extinction for a small island like Singapore. The most susceptible families are the Trogonidae and Eurylaimidae, with 100 % species loss, and Picidae, with 56.3 % species loss. The susceptible bird families are predominantly those of the forest, whereas the resistant families exist largely in open country and scrub. In fact, only three extinct species were not largely dependent on tropical rainforests for their existence. Forest species such as the Green Broadbill (Calyptomena viridis) became extinct from the forests as recently as 1941. This emphasises the role that habitat destruction has played in shaping Singapore's avifauna. Fifty-four species of birds are at risk of extinction, of which 34 species (63 %) live in the forest. The remaining patches of forest in Singapore are mostly protected in the Central Catchment Nature Reserve that should provide a safe haven for the forest birds. However, the forests are too fragmented, small and constantly disturbed by thousands of visitors. By connecting the smaller Bukit Timah Nature Reserve to the much larger Central Catchment Nature Reserve, the forest patch size can be increased and might allow more movement of animals and plants between the two patches. Many forest birds are secretive or weak fliers and are reluctant to cross open spaces. A green corridor might encourage them to do so. Another 16 species (29.6 %) of threatened birds are specialists of mangroves and wetlands. Preservation of these most-threatened of ecosystems in Singapore is of utmost importance to the survival of the birds found in these special habitats. With improvement in the quality of habitats, we could perhaps slow down the rate of local extinction of the avifauna of Singapore. Our remaining habitats need to be protected and laws protecting wildlife must be strictly enforced, so that the birds may have a chance to coexist with us.
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