Bird-dropping spider fact sheet | Field of Mars EEC

What are bird-dropping spiders?

Bird-dropping spiders are native Australian spiders in the genus Celaenia. They are named for their mottled bodies, which can look like small bird droppings when the spiders rest with their legs tucked in.

Unlike many orb-weaving relatives, bird-dropping spiders do not build a web to catch flying prey. At night, female bird-dropping spiders attract male moths by releasing a scent that mimics female moth pheromones, then grab the moth when it comes close.

Bird-dropping spiders are found through much of eastern and southern Australia, including NSW, in foliage of woodland, dry forest, gardens and orchards. They are useful for learning about camouflage, chemical mimicry, predator-prey relationships and small animals living among plants.

A bird-dropping spider

Bird-dropping spiders can be difficult to spot among leaves and stems.

Where do bird-dropping spiders live?

Bird-dropping spiders live among leaves, stems and branches where they can rest during the day and hunt at night. They are recorded from south-western and eastern mainland Australia and Tasmania. In NSW, they may be found in suitable wooded or garden habitats, but spiders can be hard to identify from a distance, so observations should be checked carefully.

Bird-dropping spiders may rest among leaves and branches with their egg sacs.

What do bird-dropping spiders eat?

Bird-dropping spiders are predators that feed mostly on male moths. A female can release a scent that imitates the pheromone of a female moth. When a male moth follows the scent and comes close, the spider reaches out and catches it. The spider uses silk for resting lines and egg sacs, but not as a prey-catching web.

Moths are the main prey of bird-dropping spiders.

What is the life cycle of a bird-dropping spider?

Bird-dropping spiders hatch from eggs into tiny spiderlings. Like other spiders, they grow by moulting, which means shedding their hard outer covering as their body becomes larger.

Females make large, round, brown egg sacs that can hang together from silk. Sources describe females producing several egg sacs, with each sac about 12–14 mm across and containing more than 200 eggs.

Female bird-dropping spiders make round egg sacs that can hang together on silk.

What adaptations do bird-dropping spiders have to help them survive?

Bird-dropping spiders have camouflage that helps them avoid being noticed. Their mottled cream, brown, grey and black body can look like a bird dropping, especially when the spider sits still with its legs folded close to its body.

Their feeding strategy is another unusual adaptation. Instead of waiting in a sticky web, the female releases a moth-like scent that attracts male moths. This is a type of mimicry because the spider imitates something else in order to survive.

Mottled colours help bird-dropping spiders blend in during the day.

Why are bird-dropping spiders important?

Bird-dropping spiders are part of food webs in woodland, garden and orchard habitats. By feeding on moths, they help keep some insect populations balanced. They may also become food for birds, wasps or other predators. Their camouflage and scent mimicry show how animals can have highly specialised adaptations for survival.

Moths are part of the food web that supports bird-dropping spiders.

How can you help bird-dropping spiders?

You can help bird-dropping spiders by protecting shrubs, trees and quiet garden spaces where spiders and moths can live. Avoid spraying pesticides unless they are really needed, because pesticides can harm spiders and their prey. If you find a spider or egg sacs, observe them without touching, moving or collecting them. Reducing unnecessary outdoor lighting can also help many night-flying insects.

Urban gardens with shrubs, trees and quiet shelter can support spiders and other small animals.

Related fact sheets

More invertebrate fact sheets

• Invertebrate fact sheets⁠ – Explore insects, spiders, molluscs and other small animals found in Sydney and NSW.
• Spider fact sheet⁠ – Learn about the features all spiders share, including eight legs, silk and predatory feeding.
• Arachnids fact sheet⁠ – Explore spiders, mites, ticks and other eight-legged invertebrates.
• Garden orb weaving spider fact sheet⁠ – Compare another orb-weaving spider from the same family.
• St Andrew’s Cross spider fact sheet⁠ – Compare another orb-weaving spider with strong visual adaptations.
• Leaf curling spider fact sheet⁠ – Learn about another spider that shelters in vegetation and catches insects.

Habitats and ecosystems

• Tree habitat fact sheet⁠ – Explore branches, bark and leaves used by many spiders and insects.
• Shrub habitat fact sheet⁠ – Learn how shrubs provide web supports, shelter and prey.
• Leaf litter habitat fact sheet⁠ – Discover ground-layer habitats that support many invertebrates.
• Eucalypt forest ecosystems fact sheet⁠ – Explore bushland ecosystems with trees, shrubs, insects and spiders.

Food webs and ecological relationships

• Moth fact sheet⁠ – Learn about night-flying insects that bird-dropping spiders can attract and catch.
• Insects fact sheet⁠ – Learn about the animal group that includes moths, flies, beetles and many spider prey species.

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