The Friends of Hullett take great effort in providing nesting habitat
for Mallard ducks. There are 38 mallard tubes installed in the Hullett
Wildlife area. During the winter, Wildlife technicians check the mallard tubes,
cleaning out old shell fragments or whole eggs, and replace the
straw in the tube. Monitoring of active nests and egg counts will
take place May-september.

Check this link provided by Delta Waterfowl for constructing your own mallard nest