I presume you mean following a days shooting at the end of a season as I can't see why you be asked to tip otherwise?
Have always understood that at the end of the season there is a 'keepers day' when the shoot captain or the esate owner will let the keeper have a day to invite his guests to come and shoot. The keepers then usually gives the hard working, underpaid, loyal members of the beating team the opportunity to shoot by way of a 'thank you'.
What appears to have developed over the years is that the beaters now feel it is their right to shoot at the end of the season and don't feel they should have to tip the keeper. You really would not believe the ammount of beaters that get the ache if the keeper actually invites a guest to shoot and that person finds themselves in the 'hot spots' throughout the day!! Some people seem to loose sight of the fact that it's not about bagging as many as you can but about being out there with a gun over your arm and a dog at your heel.
So in my opinion, and I know I am 'old school', if you are a beater and you are given that opportunity to shoot you should offer to tip. Don't faff around with the 'money in a hat' thing because there are a lot of tight fisted **** out there who don't feel they should, (or even worse will throw coins in!) and my friend you will all get tarnished with the same brush. A crisp £10 note in a hand shake is sufficient to say a small thank you for your days invitation and trust me it will speak volumes when it comes to sorting out who gets to go where roost shooting and who gets the first phone call when the pigeons are playing havock with the drill...etc. :yp:
In a mjority of cases the tip will not get accepted because it is probably not expected but even if it is what's a tenner for a days sport!...... It's just a little harder to say thanks for a day when you got soaking wet, only had one shot at a 200 yard rook, put a hole in your wellies and some idiots dog decided it wanted to ride your bitch all day!!