head-first-design-patterns | Head First Design Patterns in C | Architecture library

Yes whenever you use new keyword to allocate some memory then you must always use delete to free up that memory later when no longer needed. Otherwise you will have a memory leak as in your program. In your case you should use delete inside the destructor in the MallarDuck.cpp .

Other solution would be to use smart pointers like unique_ptr so that you don't have to explicitly free the memory.

unique_ptr`'s syntax would something like: