A tiny purple sapphire indulges in a relaxing sunbath on a cabbage leaf. A few Indian cabbage whites play hide-and-seek in a spring celebration, while a lady butterfly just lifts its abdomen and timidly rejects the advances of a courting male.
You might also be lucky enough to spot Hong Kong's largest butterflies, the common bird wing, with a wing span of 12mm-14mm - the size of two human hands - or the world's smallest species, a white dragon tail with a swallow-like tail and partially transparent wings.
Believe it or not, Hong Kong is home to 250 species of butterfly, accounting for one-tenth of the species on the mainland and half of that in Taiwan. In Tai Po, there is a special butterfly reserve. The 42-hectare Fung Yuen Valley was designated by the government as a site of special scientific interest 30 years ago. It is now managed by the Tai Po Environmental Association (TPEA) and has 80 per cent of the city's butterfly breeds.
It is also the breeding ground of 50 rare species, including the white dragon tail, forget-me-not, dark brown ace and the "butterfly star" common birdwing, which is the only species protected under the city's laws.
"Fung Yuen is not a park," says assistant project manager Colleen Chiu Yuk-lin. "But it's an invaluable gem that preserves the most natural habitat for butterflies."
In 2002, TPEA volunteers collaborated with farmers and landlords to have the area officially recognised as a reserve. Long before, though, it had been rural greenlands, mostly farmlands with a mosaic of fung shui woods and lychee orchards much loved by butterflies.
Citrus trees are one of their favourite hangouts. Some feed off the tree sap. "It's common to see a butterfly couple having a candlelight dinner here," says project officer Tam Kin-chung, pointing to a tiny hole on the tree trunk. "If not, you'll see a few of them gather around the hole for a feast, as if having a 'hotpot'."
Like most wildlife struggling to survive in Hong Kong's highly urbanised and polluted environment, these vulnerable creatures are not immune to human disturbance. Just across the road from the reserve, bulldozers and backhoes rumble at a construction site. They are working on a housing estate, due to be home to around 4,000 people.
Although the developer has promised to incorporate green features into the estate's design, butterfly enthusiasts fear they won't be enough.
"This is a disaster," says Tam. "Not only does it obstruct natural scenery and remove vegetation, the increasing human activity will worsen pollution." He explains household use of detergents, hair sprays and chemicals pollutes river water and the plants which make the nectar butterflies feed on.
"Hong Kong is not only our home, but it is also home to myriad species of wild life, and it has been since a much earlier time in history," Chiu says.
"It's really time for us to think about who the 'invader' is and how different inhabitants - human beings, plants and animals - can live in harmony."
Get your binoculars ready and go butterfly watching on a sunny day between now and next month. You need to do it before summer sets in or wait until September and October. Butterflies are most energetic at around 20 degrees Celsius.
A butterfly festival will be held at Fung Yuen on Sunday. Visit www.fungyuen.org for details