Question- last season my female (maiden bitch) began flagging around day 9 of her heat. I waited until day 11 then day 13 to breed her (proven stud). She stood very willingly, had reduced bleeding that was light in colour, and was actively flagging and showing her rear to the male, she was very swollen at this point, 1st tie was 16mins second tie was 10 mins. However, on day 14 her vulva size reduced significantly, however day 16 she started humping people’s legs, and her smell increased quite strongly. This did not result in a pregnancy. Do you think it was due to breeding her too early? Did I miss ovulation? On day 14 onwards she had no interest in males and trucked her tail between her legs although when I touched her she would still flag.any advice appreciated.

Are you progesterone testing her to find out when she is ready and a date for ovulation.

I would think you were too late try earlier next time.

I didn’t that time, I will be for future for sure though.

Reduced bleeding has no relevance.  I have a bitch who bleeds heavily right up to day 28 - even though she is pregnant.  I've never believed in the "straw coloured" bolony.

I’ve always found that the strong smell indicates ovulation.

If I was to wait for straw coloured bleeding I wouldn’t have a hope in having a litter, 11,13 days mating still very red blood and healthy litter, bleeding didn’t reduce until about day 23, her tail flagging stopped before the blood reduced.
If no longer flagging at day 14 I would say you were potentially too late in breeding.

Mine would go to a straw colour and reduced discharge AND stand when they were at the right time to be mated!  I had one, however, who had two good matings at the 'usual' time - days 11 and 13 and then came home and returned to a more blood coloured discharge although she was fine in herself.   At the time I thought she's not taken. 

She had an uneventful pregnancy and produced 9 puppies, (5 boys, 4 bitches) probably the best we had bred.  We kept 3, one of the males and 2 bitches and they came back to the UK with 4 others, including mum.  Unfortunately his edge to edge bite went full undershot but a fellow breeder so liked him that, with full knowledge of his bite, used him - twice!!  The sisters were both permanently qual. for Crufts and one took her UK Championship - a first for a Canadian bred bitch of the breed.

There are several 'text book' signs, but unfortunately, not all bitches read the text book
Progesterone testing will take the guess work away.

If you have access to the stud, you can try every couple of days until she doesn't stand any longer for breeding and you will be pretty dead cert to cover the fertile period that way.  However you will also have a very wide whelping window as you won't know when she took...

It's worth noting that, whatever the book says, there is no reason to expect a bitch to ovulate on day 10, day 14, or whatever.

I've had a bitch ovulate on day 4, and I've had a bitch ovulate on day 28.  I've had a bitch hump everything in the house from day 3, I didn't take flagging as a true "readiness" and she actually ovulated on day 16.

They do it just to let us know that they know better than us!!!