Java Sparrow

House in a long flight cage or aviary that prioritises horizontal flying room over height. Absolute minimum for a pair is about 80 cm long x 45 cm wide x 45 cm high; a breeding pair or small group is far better in 120 cm x 60 cm x 60 cm or larger, and an indoor/outdoor aviary is ideal. Bar spacing should be 1 cm or less. Provide several perches of varied natural-wood diameter placed far apart at each end to force flight (not crowded together), a shallow daily bathing dish, a covered nest box or wicker nest with soft nesting material if breeding, and a cuttlebone or mineral block for calcium. Line the tray with paper or a paper-based/aspen-type substrate that is spot-cleaned daily and fully changed weekly; avoid cedar shavings. Keep the cage draft-free, off the floor and away from kitchen fumes and aerosols.

Staple: a good-quality foreign-finch or mixed millet/canary seed blend (white, yellow, red and Japanese millet, canary seed, and paddy/unhulled rice, which this species particularly relishes). Supplement with sprouted/soaked seed a few times weekly, egg food or soft food daily during moult and breeding, and rotating fresh greens such as kale, romaine, chickweed, spinach (in moderation, as it is high in oxalates) and seeding grasses. Offer cuttlebone and a source of soluble/insoluble grit for calcium and digestion, and always provide clean fresh water. Because caged Javas gain weight easily, limit oily seeds (niger, hemp, sunflower) outside the breeding season. AVOID entirely: avocado (fatal to birds), chocolate, caffeine (coffee/tea), alcohol, salt, onion, garlic, apple/pear pips and stone-fruit pits (cyanide), and any mouldy or spoiled seed.

Birds are not reptiles, so no heat-basking spot or reptile-grade UVB is required. Keep ambient room temperature comfortable and stable at roughly 18 to 24 C (65 to 75 F). Javas are reasonably hardy and, once fully acclimated, tolerate cooler conditions down to around 10 to 15 C, but they must never be exposed to frost, sudden temperature swings or cold drafts; do not let temperatures fall below about 10 C. Maintain moderate humidity of roughly 40 to 60 percent; very damp, stagnant air encourages respiratory fungal disease and mites. Provide 10 to 12 hours of light and a genuine dark rest period at night; a full-spectrum avian lamp is a useful bonus for indoor birds to support natural behaviour and vitamin D but is not strictly mandatory if a varied diet and natural daylight are available.

Highly social and gregarious. Never keep a Java Sparrow permanently alone; house as a bonded pair or in a small compatible group. They are generally peaceful but can bully smaller finches and may squabble over nests when breeding, so give ample space and multiple feeding stations in mixed aviaries. The sexes look almost identical (monomorphic): mature males sing a soft clicking, bubbling song while females do not, males often have a slightly deeper, more swollen red bill, and pair-bonded birds noticeably brighten and enlarge their red eye-ring. DNA sexing is the only reliable method if breeding is planned.

Flight is the single most important enrichment, so a long cage or aviary with well-spaced perches matters more than toys. Offer a daily shallow bath (they love to bathe), millet sprays and foraging opportunities, fresh natural branches to perch and nibble, seeding grass heads to work through, and the constant company of their own kind. Rotating greens, swings and safe natural materials keep active minds and bodies occupied and help prevent the boredom and obesity of under-stimulated caged birds.