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How to Candle Wild Duck Eggs

Candling is the process of using a bright light to examine the embryo inside an incubating duck egg. Candling helps determine the age of the embryo and estimate the hatching date. Infertile eggs and eggs with dead embryos are discarded. Egg candlers usually consist of a lightbulb inside an enclosure. The enclosure has a small hole and the egg is placed next to the small hole. Candlers work best in a very dark room. Candling is most accurate in the first half of incubation.

Instructions

- 1
  Research and observe United States federal and state laws about disturbing wild duck eggs and nests. Permits are usually required.
- 2
  
  A candler may be as simple as a small, powerful flashlight.
  
  Purchase or construct an egg candler for wild duck eggs. A candler may be as simple as a ½-inch small, powerful flashlight held against the egg. Commercially built candlers may consist of a lightbulb inside a metal canister.
- 3
  
  Place a lightbulb and porcelain socket inside a wooden or cardoard box or coffee can.
  
  Construct an egg candler for wild duck eggs by placing a lightbulb and porcelain socket inside a wooden or cardboard box or a coffee can. Cut a small hole in the top or side and place the egg against the hole.
- 4
  Observe clear, distinct veins in the wild duck embryo. This is a characteristic of living embryos. The embryo should have a spider-like appearance, with the embryo being the spider's body and the large veins resembling spider legs. If the veins are not clear and distinct, the embryo may not be alive. A dead embryo may have a blood ring around it. Infertile duck eggs are clear with a slight yolk shadow.
- 5
  Candle the duck eggs every few days to chart its development. Wood duck eggs have an incubation period of about 28 days. During the first and second day of incubation, the yolk becomes darker. By the fifth day, the heart is beating and by the seventh day, the air sac suddenly increases in size. The eye spot is 4 to 5 mm in diameter by the tenth day. The legs move frequently by the 12th day. By day 19, most of the egg is black, filled by the developing duckling.
- 6
  Estimate the size of the developing wood duck embryo to determine the stage of development. By the sixth day of incubation, the embryo is 6 to 7 mm long. By day 16, the embryo is about 19 mm long.
- 7
  Research pictures and descriptions of other wild duck embryos. A wood duck is a colorful example of a wild duck in North America. There are also readily available guides to the daily development of mallard duck eggs; they show pictures of candled eggs each day of development.

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