I have heard of silent heats, but I have never experienced one with any of my girls. I think with split heats, the dogs rarely get pregnant.
Super dog can do it in two seconds. The rest of them usually start by sniffing and have a few faied attempts to mount. You will most likely see the bitch flag her tail, and she will stand for the dog. Even then the tie is not instantaneous and if you remove them before the tie, you are very likely to not have puppies. Very likely is not 100% as there may be sperm in the first section of fluid.
If you are accustomed to accompanying your bitch to the park, then you should be able to spot the change in behavior of your dog and other dogs toward her. Everyone will be much more than just a sniff greeting, usually there will be lickly and grooming. An experienced dog can go from 0 to 10 a lot quicker, but I really don't think it would be so quick that you would not be able to get a reasonable distance.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC