Face Value	ISC	Michel	YT
20 sen	1063	1311	1084
30 sen	1064	1312	1085
40 sen	1065	1313	1086
50 sen	1066	1314	1087
75 sen	1067	1315	1088
RM 1	1068	1316	1089
RM 2	1069	1317	1090
RM 5	1070	1318	1091

Perforation: comb 13¾ x 14

This set is particular pricey despite being its definitive nature and commonly found. I have asked around and I got these answers to speculate why:

1. Topical interest, high worldwide demand from avid bird-themed stamp collectors.
2. Hoarding. Malaysian collectors have a tendency to hoard anything that is in demand.
3. These are technically definitives where 20 sen, 30 sen, 50 sen, RM1 and RM5 can be easily found BUT 40 sen, 75 sen, RM2 were never reprinted (making them scarce considering they are definitives) due to various issues of communication between the stamp supply department and philatelic department. 
4. The first print of these stamps can be easily identified by their inverted SPM watermark - adding interest to their collectibility.

The initial print were printed in a philatelic "sheet" (sheet of 20 rather than 100) and the printing quantity is the same as any commemorative stamp issue. Only when the initial prints are exhausted, sheets of 100 appear at the counters. 

The 40 sen, 75 sen and RM2 values of this set were never printed in sheets of 100.

Inverted SPM watermarked,

SPM is the abbreviation of Security Printer of Malaysia.

CREDIT

ausfoo, Georgia, USA
Ian's Collection, http://kajang-stamps.blogspot.com/2009/03/malaysia-spm-watermark.html
 

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20 sen - Spotted Dove (Streptopelia chinensis)

These birds are between 30cm and 31cm in size. The crown and the sides of adult's head are grey, have a grey-auburn tinge on the upper part and are long black broadly streaked, which are iridescent bordered. The nape of its neck is black spotted with white and have pinkish-brown underparts. In flight, they reveal the white tips of their outer tail feathers. The juveniles are of darker auburn, have duller grey crown and plumage on their wings. They lack colour on their collar / neck with small brownish dull yellow stripes and are common and widespread in open grassland and secondary forests. They are also found in scrub vegetation and gardens up to 2,040 metres. They breed all year round and are multi-brood. Their nest is a flimsy stick platform in a tree, tall bush or on bamboo cluster. They lay 2 or 3 eggs sized 26.9 × 20.8 mm on average.

30 sen - Ochraceous Bulbul (Alophoixus ochraceous)

These birds are between 19 cm and 22 cm in size. The adults are puff-throated with small and short upright crest. They have warm brown upperparts with yellow absent from their lowerparts. They frequent evergreen forests up to 1,525 metres and are normally found in the mid canopy strata of the forest usually in pairs or small flocks. Their breeding period is between February and April. A typical clutch of two slightly glossy pinkish-white and almond red eggs measuring 25 × 17.5 mm are laid in deep cup-shaped nests about 2.4 metres from the ground. They are found in most of South-East Asia.

40 sen - Long-tailed Parakeet (Psittacula longicauda)

These birds are between 40 cm and 42 cm in size. The males have reddish sides of head with black mandible. They have green crown, dull blue wings and pale -blue-green back with long blue-purple and narrow tail feathers. The females are with green nape, darker green crown and upperparts. They have dull ginger bill and dark green narrow band. Tail feathers are much shorter. Juveniles have pink face with duller green narrow band. The bird usually frequent open green wide leaves forest such as peat swamp forests, second growth, mangrove swamps and lowland areas. They breed between December and July laying 2 or 3 eggs sized 30.6 × 24.7 mm and nest in holes in tall trees 4 metres to 45 metres above the ground. They are found in Andaman Islands, Nicobar Islands and most of South-East Asia

50 sen - White-rumped Shama (Copsychus malabaricus)

These birds are between 21.5 cm and 28 cm in size. The head, breast and upperparts of the males are iridescent blue-black. the underparts are dark orange-rufous. The females are similar to the males but they are more greyish and duller with a reddish brown underparts. The juveniles have pale yellow blotchy upperpart with pale yellow spots on the wing plumage, wide pale yellow blotches are also present at the tips of their wings as well as their neck and they have a dark diluted yellow breast. They can be located in broadleaved evergreen and mixed deciduous forest, secondary forest and bamboo forest at a height of 1,525 metres. They are great bathers and their plumage is usually kept in immaculate condition. They breed between the months of March and September. Their nests are near cup-shaped, inside hollowed tree trunk or on bamboo culms about 2 metres from the ground and they lay 4 or 5 blue-green eggs. Their territory includes India, Southwest & South China, Greater Sunda and Southeast Asia.

75 sen - Olive-back Sunbird (Nectarinia jugularis)

These are very small birds, sized at about 11.5 cm. The upperparts of a male are dull olive brown, metallic blue-black forehead, throat and upper breast (with red stripe edge), contrasting with bright yellow underparts and white undertail. The females have a decurved bill with all white tail. The bird is common in woodland, secondary forests, marshes, mangrove swamps, coastal scrubs, gardens and vegetations up to 915 metres. They build a flimsy hanging pear-shaped nest with an overhanging porch at the entrance between 1 metre to 9 metres above ground. They lay two greenish-grey or pure grey eggs speckled with light purple-brown or deep purple-brown spots sized at 16.6 × 11.5 mm on average. Found in the region stretching from southern Myanmar to Northern Australia and the Philippines.

RM1 - Green-winged Pigeon (Chalcophaps indica)

These are medium birds at about 25 cm in length. The male have blue-grey crown and nape with white forehead and eyebrow and red bill. They have iridescent metallic green mantle with white scapulars. head and underparts are vinous-pinkish. They also have two prominent white transverse bars on the rump. The females have duller grey crown. Young birds are darker with small yellowish brown stripes and unlike the adults which has greenish wings. These birds can be found in lowland dipterocarp forests and coniferous forests up to 1,500 metres. The birds would usually perch under tree cover and will scuttle quickly at the slightest hint of danger. The birds can be found in the Indian subcontinent (except Pakistan), China, Taiwan, Sunda Islands, Philippines, Peninsular Malaysia, Celebes, New Guinea, Australia, Vanuata, New Caledonia, Norfolk Island and Lord Howe Island.

RM2 - Banded Pitta (Pitta guajana)

These birds are between 21 cm to 24 cm in length. The male is easily recognisable for its black crown and black eye-stripes. There are bright yellow lateral crown-stripes and malar-stripes, which turns into reddish orange streaks, which are especially visible on its chest and the sides. While the female chests are white, they have grey lower belly. They have fine black stripes on the white feathers. Their upperback is reddish-orange but duller than the male. The young birds have dark brown chest with grey mottling or fine grey streaks. Banded pitta are endemic in virgin and logged lowland forests, up to 610 metres. The breeding period is from February until November and they lay 2 to 5 glossy white eggs. Their nests are round with an opening at the side built on palm trees or in between young trees about 3 metres above the ground. Their territory includes Greater Sunda, Southern Thailand and Peninsular Malaysia.

RM5 - Imperial Pigeon (Ducula aenea)

These are large plump pigeons between 42 cm and 47 cm. Their back, wings and tail are iridescent red-almond. They have dull grey-grape crown, neck and underparts, dark almond undertail coverts. They are mostly found near rivers, forages in small groups, feeding on plant material in the tree canopy and is recognised by its deep resonant call. They breed between the months of January and May, as well as September. Their nests are poorly constructed flat platform of twigs in a tree and sometimes on bamboo clumps about 10 metres from the ground. The female lays 1 or 2 white eggs measuring 45.5 × 33.5 mm on average.