We have charts for each bird with the date, weight, feed given (and weight of feed), how they worked and any other comments - it's really useful to look back at how they've come on over the last few months and at what weights they have worked best.
Once you've been on a bird for a while you get to know their flying weight so that they are keen to fly but not underweight which can be dangerous and make the bird weak.
At the right weight she'll be reaponsive, motivated and come to the glove when called; if she's overweight she won't be hungry and will often sit on her perch or wait around for a few seconds before coming after being called.
Františka flys best at around 950g but back in September she was 1300g so we cut her food intake and started working with her to the point that she will now free fly and recall to the fist.
We're having to fly the birds later in the afternoon now it's getting hotter as they don't cope very well.
When it gets really hot, 30oC plus, we'll perch them out early and late but keep them in their news between 11am and 3pm.