Northwood Hideaways recommend boxes constructed from structural plywood rather than MDF. Not only is structural plywood stronger and more durable than MDF, it also has a natural wood grain texture that can provide a more natural look and feel to the nesting box, which can be important to attract birds.
MDF is made from wood fibers that are bonded together with resins, which can contain formaldehyde and other harmful chemicals. As MDF ages or is exposed to moisture or heat, it can release these chemicals into the air, which can be harmful to birds.
When purchasing your boxes, it is important to choose materials that are safe and non-toxic for birds.