A treat that is common in the Philippines, that you might find of interest .
Mallard ducks are used extensively in the production of balut .
Balut (spelled standardized as balot) is a developing bird embryo (usually a duck) that is boiled and eaten from the shell. It originated from and is commonly sold as street food in the Philippines. Often served with beer, balut is popular in Southeast Asian countries.
The Tagalog and Malay word balot means "wrapped". The length of incubation before the egg is cooked is a matter of local preference, but generally ranges between 14 and 21 days.
The eating of balut is controversial due to religious, animal welfare, and human health concerns.
Description,Veins in a freshly boiled, peeled Balut egg
A balut is a fertilised bird egg (usually a duck) which is incubated for a period of 14 to 21 days depending on the local culture and then boiled or steamed. The contents are eaten directly from the shell. Balut that are incubated for longer periods have well-developed embryo and the features of the duckling are recognizable. The partially-developed embryo bones are soft enough to chew and swallow as a whole.
Balut is a common street food in the Philippines and other localities, and is also sold in stores and malls. It is a relatively cheap source of protein and calcium.[3] Balut was introduced to the Philippines by the Chinese around 1885 and since then, balut has been included as a traditional part of the culture.[4] Wherever Filipinos migrated for work, a large market for balut would develop.
Traditionally, the fertilized eggs are incubated in the sun or buried in sand, and stored in baskets to retain warmth. Some pictures for those who want to see it.
https://www.bing.com/images/search?q=balut&qpvt=balute&FORM=IGRE