Duck Eggs and Salted Eggs!

Proportionally larger to a regular hen egg, and with a blueish green tint to its shell, the duck egg ( pictured above) is far richer than it's chicken counterpart.

For the most part, duck eggs are significantly more expensive as compared to hen eggs. And fresh duck eggs are rarely if not completely not found in the Singaporean market anymore!
Duck eggs were widely used in Singaprorean hawker fare till the 80s, but hawkers have since used chicken eggs as they are more cost effective.

The only significant form of duck eggs that we see on the market are in the form of salted eggs. ( As pictured below, in market form)

Salted duck eggs are made by soaking the fresh eggs in a brine solution for a period of time. This results in a firm textured and round yolk that is bright orange and red. Unlike fresh duck eggs, salted duck eggs are widely found on the market, and can cost between $2 to $2.50 for 4 eggs. 

Needless to say, both fresh duck eggs and Salted duck eggs are widely used in Asian cuisine. For example, Balut, from the Philippines ( using fresh duck eggs with embryos) and Salted egg yolks in mooncakes eaten during the mooncake festival.