Here is everything I found on the internet on vent sexing Geese and Ducks. I will also post pics of my own soon on vent sexing if I can get some clear pics of the procedure... I'm going to vent sex Sebastopols at 1 week, and then every month or so and will post the pics on this thread. For now here are all the pics and articles I found on vent sexing them. This does come with a disclaimer... You must understand you could hurt your bird if this is done incorrectly so before you do it on your own it is best for an experienced person to show you in person on how to do it... Try at your and your pets own risk! Method of holding day-old goslings to expose their reproductive organs (Source: Hunter & Scholes) FIGURE 15. Male (left) and female (right) reproductive organs of day-old goslings (much enlarged) (Source: Ontario Ministry of Agriculture and Food) If geese are to be sexed as adults, the recommended procedure is that each goose be caught, lifted by its neck and laid on its back, either on a table or over the operator's bent knee, with the tail pointed away from the operator as shown in Figure 16. FIGURE 16. Method of holding adult geese for sexing (Source: Ontario Ministry of Agriculture and Food) The tail portion of the bird should be out over the edge of the table or over the operator's knee so it can be bent downwards easily. The operator then inserts his/her index finger (sometimes it helps to have a little Vaseline on it) into the cloaca about 1.0 to 1.5 cm and moves it around in a circular manner several times to enlarge and relax the sphincter muscle which closes the opening. Next, pressure is applied both directly below and to the side of the vent in order to expose the sex organ as shown in Figure 17. In some birds the male organ is somewhat difficult to unsheathe, particularly if the birds are either immature or not in semen production. For this reason an inexperienced sexer can easily mistake a male for a female if, after slight pressure, the phallus is not exposed. Only the presence of a female genital eminence will positively identify a female. FIGURE 17. Exposed reproductive organs of mature male (left) and female (right) More diagrams: Different vent sexing method I found: Sexing diagram and instructions Vent Sexing an adult Referenced from: Jessica at publicfotki.com Here's the description for the picture (with a Toulouse illustrated). The first thing you want to do is grab the goose and sit down with it between your legs and close to your body as shown. Have the goose facing you in the sitting position and and place your left fore arm over the wings (to prevent the goose from flapping about or moving, and to keep the goose in the sitting position) and your left hand between the goose's leg joint/ leg, and the body. The goose may or may not want to tuck it's head under your arm, but it might be easier if you have it there anyway. Your hand should be near or touching the pubis bones. Now take your right hand and grab the leg (still bent) and gently slide, or pull it away from the body. The goose should begin twitching it's tail. When it does this, you want to either hold that position, or pull the leg further until the goose gives a hard thrust. You may use your left hand to apply pressure or massage the area while your right hand holds the leg, to get a better reaction. You may want to induce several hard thrust from the goose to make sure you get a good result. If it is a gander, the penis will be clearly visible. If you look while the gander is thrusting, the penis will probably look like the illustration. If you look after the thrust, you will see the penis coiled or the tip of the penis in the cloaca/vent . If it is a female, there will be nothing. When performing this procedure you can actually roll the goose on it's side as it is thrusting and it will remain in that position, for easier viewing, or even perform the procedure with the goose on it's back. It's kind of hard to describe the procedure, but it's actually very simple and much more comfortable for the birds. The reason the birds do this is because it feels like when they are mating. When they are mating, and when the gander is thrusting him self into the female, he tucks her tail or lower rump between his leg and his body ,pulls and holds her vent to his like this. This is what he is doing when he jerks his bottom half into the water during mating, to reach the female. Check back for my photos I will be adding soon of my own goslings and then adult Sebastopol. If anyone else has good pics please post them... I believe it is more in the goslings favor for you who are experts to show us pics and let others know your technique then it is for someone to blindy try to teach themselves... So please share your advice, technique, and photos... Thanks (THIS IS SUPPOSE TO WORK ON ALL WATERFOWL EXCEPT WILD BREEDS) HERE IS ANOTHER THREAD I FOUND WITH PICS: https://www.backyardchickens.com/forum/viewtopic.php?id=75366&p=1 Here is are a couple of males I have less than a week old... It's so hard to hold the vent just right so that the penis will come out and work the camera at the same time... So here is what I think is a little male; Notice the tiny little pointy worm sticking out... Females will not have this.