Weigh the same way, at the same hour, every week
A weight log only detects change if the weighing itself never changes. Use the same scale each time — a kitchen scale with a perch fixed to it, or a flat scale your parrot will stand on for a favourite treat — and weigh before the first feed of the day, because a crop full of breakfast can add a misleading lump to the figure. Note the weight and date together, every time, even when the number looks boringly identical.
Teach the routine as a trick, not a capture. A parrot who is grabbed and placed on scales weekly learns to dread the sight of them, and a struggling bird gives a swinging, useless reading. A bird who steps onto the perch scale for a nut sliver gives you a still figure in seconds and will cooperate for years.
Build your parrot's own normal range first
For the first eight weeks or so, the log's job is not alarm — it is calibration. Healthy parrots hold a fairly steady personal weight with small daily wobbles, and that steady band, your bird's own range, is the only comparison that matters. A species chart can tell you a weight is broadly typical, but it cannot tell you that this particular bird has sat at the same figure for two months and has now moved, which is the information that catches illness early in an animal who hides weakness by instinct.
Write down anything that legitimately moves weight beside the entries it affects: a moult, a diet conversion in progress, a spell of hormonal behaviour with reduced appetite, extra flight exercise after a cage change.
The changes that mean call the vet now
Treat two patterns as same-day phone calls, not wait-and-see. The first is size: a sudden loss of roughly a tenth of your parrot's usual body weight over a short period is a serious change in a bird, even if he still looks bright. The second is company: any clear downward step arriving with behaviour change — sitting fluffed, sleeping more, a quieter voice, food left in the bowl, droppings reduced or altered — means the weight is confirming what the behaviour suggests, and birds presented early do far better than birds presented once they can no longer hide feeling ill.
Do not wait for the scheduled weigh day if you notice those signs midweek; weigh at once and make the call with the log's figures in hand. Tell the vet the usual range, the current figure, and over how many days it fell. That short history, which only a kept log can supply, helps the vet judge urgency and gives the first examination a baseline to work from.
Keep the log where the vet can use it
Store the log with your parrot's other health paperwork rather than on a scrap by the scales, copying the figures across weekly or keeping the log itself in the health folder. Trends are only visible on a page that holds months together, and a vet reviewing a year of stable weights interrupted by one fall reads the situation in seconds.
Weighing takes a minute a week, yet it is one of the few home checks that detects trouble while it is still small and correctable. Keep the habit unbroken through healthy years, because the log you need is the one started long before anything was wrong, and KinsLe Pet Passport keeps that weight history alongside your parrot's other health records so the whole trend travels to any vet appointment in one packet.