Scale everything down for a bird this small
A Java sparrow weighs about as much as a few coins, so his first aid supplies must be finch-sized rather than simply a smaller version of a parrot kit. Keep plain cornstarch for stopping a bleeding toenail or broken pin feather, because it is gentle, easy to dust onto a tiny foot, and already familiar from the kitchen. Stock small gauze squares you can fold to fingertip size, cotton buds for pinpoint application, and sterile saline in a dropper bottle so you can rinse a grazed leg one drop at a time instead of flooding a frightened bird. Fine tweezers help lift a thread wrapped around a sparrow's slender toe, a common accident with loose nesting material, and a magnifier or phone torch makes those thread-thin legs easier to inspect without handling him longer than necessary.
Warmth and calm are the real medicine for a sparrow
Shock and heat loss threaten a Java sparrow faster than most minor wounds do, so his kit should include a small hospital cage or spare cage kept ready with a plain perch and a cover cloth. A wrapped warm water bottle or heat disc placed against one side of that cage lets the sparrow move toward or away from the warmth as he needs. Covering the cage to dim the light settles a finch quickly, and handling should be planned down to seconds: catch him gently with a soft, lightweight cloth, do the job in one calm attempt, and release him into the warm hospital cage rather than back into the flight with flock mates who may peck at a blood spot. Keep the kit in the same room as the cage and learn the routine on a quiet day, because a sparrow chased around a flight for five minutes arrives at treatment already exhausted.
What the kit handles, and what it cannot
A Java sparrow's kit copes with a bleeding nail after a clumsy landing, a pin feather knocked during a night fright, or a thread around a toe caught early before swelling starts. Rinse a small wound with saline drops, press cornstarch gently against a bleeding nail tip, and then leave the bird warm, covered and undisturbed while you watch from a distance. Offer his usual seed and a shallow water dish in the hospital cage, and check that he is hopping and eating before returning him to the flock. If a thread has already cut in or the toe looks swollen or discoloured, do not keep unwinding at home; that leg needs an avian vet's steadier tools and magnification.
When a Java sparrow needs a vet, not first aid
A Java sparrow who sits fluffed on the cage floor, breathes with his beak open, cannot perch, or keeps bleeding after gentle cornstarch pressure needs an avian vet the same day, because a bird this small has almost no reserves to wait on. Night frights that leave several flock members injured, or repeated leg-thread accidents, also deserve a vet's advice on the cage setup itself. Write your vet's number and your sparrow's leg band details on a card inside the kit lid so a family member can act without searching. Keeping his KinsLe Pet Pass with the kit puts his identity and your contact details on one verified card, so whoever helps him in a crisis can identify him and reach you without delay.