The Southern Birdwing Butterfly Explained

The southern birdwing (Troides minos) is the largest butterfly in India, a spectacular swallowtail of the Western Ghats whose velvety black forewings and golden-yellow hindwings can span well over 14 cm, and it was declared the state butterfly of Karnataka in the mid-2010s. The southern birdwing flies slowly and high above the forest canopy, descends to flowers in the monsoon and post-monsoon months, and lays its eggs only on pipevines of the genus Aristolochia and their relatives, whose toxins also make the adult butterfly distasteful to predators.

This explainer describes what the southern birdwing looks like, where it lives, how it breeds and why it needs specific host plants, how it differs from other birdwings in India, and why its conservation matters. Last updated 22 October 2026.

Key Takeaways

• The southern birdwing is the largest butterfly in India, with a wingspan that can exceed 15 cm and is larger in females than in males.
• The southern birdwing is native to the Western Ghats of south-western India and is the state butterfly of Karnataka.
• The southern birdwing has black forewings and golden-yellow hindwings marked with black spots, a pattern that is brighter in the male and heavier in the female.
• The southern birdwing lays its eggs on Aristolochia pipevines, and its caterpillars absorb toxic compounds from these plants that deter predators.
• The southern birdwing flies with a slow, soaring flight high in the canopy, and it comes down to feed on flowers mainly in the rainy and post-monsoon seasons.
• The southern birdwing is legally protected in India, and its long-term survival depends on keeping Western Ghats forest and its host vines intact.

What Is the Southern Birdwing?

The southern birdwing is a large swallowtail butterfly in the family Papilionidae, belonging to the birdwing group, and it is the largest butterfly found in India. It is called a birdwing because its big, elongated forewings and its slow, gliding flight remind observers of a small bird in the air.

The species is confined to the hill forests of peninsular India, mainly the Western Ghats, which are a recognised global biodiversity hotspot. Within India, the southern birdwing is the most southerly of the birdwings, and it is found alongside famous Western Ghats butterflies such as the Malabar banded swallowtail and the Malabar tree nymph.

Meaning of the name

The scientific name Troides minos places the butterfly in the genus Troides, one of several birdwing genera in Asia, and gives it a species name taken from a figure in Greek mythology. The English name southern birdwing distinguishes it from the golden and common birdwings of northern and north-eastern India.

How Big Is the Southern Birdwing?

The southern birdwing is the biggest butterfly in India, with a wingspan that is commonly given as roughly 14 to 19 cm, and females are noticeably larger than males. Wingspan varies between individuals and sources, so the figures should be read as approximate ranges and not as exact limits.

The sheer size of the butterfly means that it is sometimes mistaken for a bat or a bird in flight. The wings are long and angular, and the body is stout, with a bright yellow abdomen in the male that stands out in the shade.

What Does the Southern Birdwing Look Like?

The southern birdwing has velvety black forewings with pale veins and golden-yellow hindwings marked with black spots, and the contrast between the dark and golden areas makes it one of the most recognisable butterflies in the Western Ghats. The body is black on top with a yellow underside.

Male and female

The golden hindwing patch is visible from a distance when the butterfly flaps through a forest gap, and it is the best field mark to separate the southern birdwing from other large swallowtails.

Where Does the Southern Birdwing Live?

The southern birdwing lives in the evergreen and semi-evergreen forests of the Western Ghats, from Maharashtra and Goa in the north through Karnataka and Kerala to Tamil Nadu in the south. It is mainly found in humid hill forest, forest edges and shaded valleys, and it avoids dry open country.

It is most often recorded in places where the forest is intact and Aristolochia vines are present. Well-known areas for butterfly watching in the Western Ghats include forest belts in the Uttara Kannada, Shivamogga, Chikkamagaluru, Kodagu, Wayanad and Nilgiris regions, but the butterfly can appear wherever suitable habitat remains. Populations may be local, and records of the species outside the Western Ghats should be verified.

Elevation and season

The southern birdwing occurs from the lowlands to mid-elevation hill forest. Adults are seen throughout much of the year in favourable sites, but sightings peak during and just after the monsoon, when flowering plants provide nectar and new leaves of the host vines appear.

What Does the Southern Birdwing Eat?

The adult southern birdwing drinks nectar from flowers such as lantana, ixora, hibiscus and other brightly coloured blooms, while its caterpillars feed only on the leaves of Aristolochia vines and related plants. The adult, because of its size, usually hovers or clings to the flower and flaps its wings slowly as it drinks.

Males, like many butterflies, are also known to visit damp ground and take up minerals, a behaviour called mud-puddling. Both sexes are attracted to flowers that are rich in nectar and have enough space to support a large butterfly. They can be seen at forest edges, gardens near forest, and plantations adjacent to natural vegetation.

What Are the Host Plants of the Southern Birdwing?

The host plants of the southern birdwing are pipevines in the family Aristolochiaceae, such as the Indian birthwort (Aristolochia indica), known locally as ishwarmul, and related climbers found in the Western Ghats. The female lays her eggs on the leaves and tendrils of these vines, and the caterpillars eat the leaves as they grow.

These plants contain aristolochic acids, which are bitter and toxic to many animals. The caterpillar stores these chemicals in its body, and the compounds are passed to the adult butterfly. As a result, birds and other predators that attempt to eat southern birdwings learn to avoid them. This is a standard example of chemical defence, and the butterfly’s bold colouring acts as a warning signal known as aposematism.

Why the vine matters

Because the southern birdwing depends on specific host plants, the loss of those vines means the loss of breeding sites, even if nectar flowers are plentiful. Gardeners and forest managers who want to encourage the butterfly can protect native Aristolochia species in the wild, rather than removing them as weeds. The plants have also been used in traditional medicine, and overharvesting may add to the pressure on the vines.

Caution is advised: aristolochic acids are harmful to humans and are associated with kidney damage, so these plants should not be used as home remedies.

How Does the Southern Birdwing Breed and Develop?

The southern birdwing goes through complete metamorphosis, passing from egg to caterpillar to pupa and then to winged adult, and the entire cycle takes roughly two months or more depending on temperature and rainfall. Each stage lasts a different length of time, and the larval stage is the longest period of active feeding.

The durations are approximate and depend on climate. Breeding can occur across many months in a stable, humid forest.

How Does the Southern Birdwing Fly?

The southern birdwing flies with slow, powerful wingbeats and long glides, often at the top of the canopy, and it may soar out of reach before dropping to flowers at lower levels. This flight is energy-efficient and fits the butterfly’s heavy body and large wings.

The high flight is partly why the butterfly is hard to photograph and why many people notice it only when it descends to feed. Males patrol territories along forest edges and streams, and females fly lower when searching for host vines. The wing shape is different from that of smaller, rapidly fluttering butterflies, and a patient observer can learn to identify the species from its silhouette alone.

How Is the Southern Birdwing Different from Other Indian Birdwings?

The southern birdwing differs from India’s other birdwings mainly in range and in the pattern of its hindwings: it lives in the Western Ghats of the south, while the golden birdwing and common birdwing are found in the north and north-east. India has three species of Troides birdwing, and all are large, yellow-and-black butterflies.

Because ranges differ, a large yellow-and-black butterfly in the Western Ghats is very likely to be the southern birdwing, while one in Assam or the Himalayan foothills is likely to be one of the northern species.

Is the Southern Birdwing Protected and Threatened?

The southern birdwing is legally protected in India under the Wildlife (Protection) Act, 1972, which prohibits collecting, killing or trading protected butterflies, and birdwings of the genus Troides are also covered under the international wildlife trade convention CITES. The exact schedule in the Indian Act has changed through amendments, so readers should consult the latest text of the law.

The main threats are loss of Western Ghats forest through clearing and fragmentation, the removal of Aristolochia host vines, pesticide use in neighbouring plantations, and illegal collection for the specimen trade. Because the species depends on a particular habitat and plant, local populations may decline even if the overall species is not at immediate risk. Population estimates are uncertain and should be treated with caution.

How can you help the southern birdwing?

• Protect native forest patches and stream corridors in the Western Ghats.
• Avoid cutting down Aristolochia vines near forest edges and gardens.
• Reduce pesticide use around plantations and homes.
• Never buy or sell butterfly specimens, which is illegal for protected species.
• Record sightings on citizen-science platforms to help researchers track the species.

Why Did Karnataka Choose the Southern Birdwing as Its State Butterfly?

Karnataka chose the southern birdwing as its state butterfly because the species is a striking, locally occurring emblem of the Western Ghats, which run along the state’s western edge and hold much of its forest biodiversity. The declaration, made in the mid-2010s, was among India’s early state butterfly designations and aimed to draw attention to butterfly conservation.

Several other states have also named state butterflies, and the idea is to build public interest in insects that are often overlooked. A flagship species such as the southern birdwing can help protect the whole forest community that surrounds it. Readers needing the exact date and notification should consult the Karnataka government’s records.

Bottom Line

The southern birdwing is India’s largest butterfly and a living symbol of the Western Ghats, its golden wings and slow canopy flight depending on a narrow chain of host plants, forest cover and clean air. Protecting the species means protecting the shaded hill forests and the Aristolochia vines that sustain it.

Frequently Asked Questions

What is the southern birdwing butterfly?

The southern birdwing is a large swallowtail butterfly, Troides minos, found in the Western Ghats of India. It has black forewings and golden-yellow hindwings and is the largest butterfly in India. It is also the state butterfly of Karnataka.

How big is the southern birdwing?

The southern birdwing has a wingspan of roughly 14 to 19 cm, which makes it the largest butterfly in India. Females are larger than males. Exact sizes vary between individuals and sources.

Where is the southern birdwing found?

The southern birdwing is found in the evergreen and semi-evergreen forests of the Western Ghats, from Maharashtra and Goa to Karnataka, Kerala and Tamil Nadu. It prefers humid hill forest and forest edges. It is not found in dry open country.

What plants does the southern birdwing caterpillar eat?

The southern birdwing caterpillar eats the leaves of Aristolochia pipevines and related plants in the Aristolochiaceae family, such as the Indian birthwort. The toxins in these plants make the caterpillar and adult distasteful to predators. Without these vines, the butterfly cannot breed.

Which state has the southern birdwing as its state butterfly?

Karnataka has the southern birdwing as its state butterfly. The designation was made in the mid-2010s. It highlights the importance of Western Ghats biodiversity.

Is the southern birdwing protected by law?

Yes, the southern birdwing is protected in India under the Wildlife (Protection) Act, 1972, and birdwings of the genus Troides are covered by CITES. Collecting, killing or trading the butterfly is prohibited. The exact schedule has changed through amendments, so the latest text of the Act should be checked.

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