Hello and welcome. My name is ***** ***** I'm a biologist with a special interest in birds. It sounds like Sunny presented you with a surprise. At this point, you don't need to do anything except provide the parents with a good diet and a clean cage.
Canary breeding can be more challenging than breeding some other bird species. Canaries reach sexual maturity at about nine months of age, but that doesn't mean they'll want to breed then. When they will breed depends on the number of daylight hours. In birds exposed to natural light, the breeding season is likely to begin in most areas sometime in February. Artificial light can interfere with normal breeding seasons. There are many potential problems when breeding canaries. Egg binding is common even in well-cared-for canary hens. Once eggs are laid, they are not likely to all be fertile - some won't hatch. The babies begin hatching about 14 days after the hen starts sitting on them. That's when the first one hatches. The eggs that were laid later will produce smaller babies that may not survive. The father usually helps to care for the babies, but if other birds besides the parents are in the cage, they may injure the young ones.
That extra large egg may have two yolks in it, which probably won't develop properly. If there's only one, and it does develop, it may be a larger chick. You can tell if eggs are fertile by candling: checking eggs by holding them up to a bright light is called candling. Experienced chicken and bird breeders can candle eggs to tell if they're fertile, but it can be difficult for a beginner to identify what they see. Candling is basically shining a bright light through the egg in a dark room to see what's inside. At the large end of the egg, you should be able to see blood vessels. An embryo will appear as a dark spot in that area. If the eggs are less than about 8 days old, you won't be able to see an embryo. Hands must be thoroughly cleaned and rinsed before handling the eggs. You can read more about how to candle, including the type of light to use, by scrolling down about halfway (past the ads) on the following page:
To read more about canary breeding:
If you have more questions about this, just let me know. I hope all will go smoothly.
My goal is to provide you with excellent service – if you feel you have gotten anything less, please reply back, I am happy to address follow-up questions. Please remember to rate my service only after you have all the information you need. Thank you!