Gerald Cunningham of Lauder asks :-
Why do birds build nests that are identical to their species? Where does the nest design and building knowledge come from in the bird?
Ian Jamieson, a zoologist at the University of Otago, responded.
Your question is at the heart of the classic nurture vs nature debate: which is more important the environment and up-bringing in which animals lives, or their genes and innate behaviour they express?
As you rightly note, each species of birds builds a nest that is more similar within the species than across species. However, you'll also note there are similarities among families of birds, (ie ones that are closely related) suggesting that their ancestry might explain some of that similarity.
Each bird can build a nest from scratch, even in the first year of breeding and it has never done so before. This suggest that its genes must play an important role. However, scientists have noted that in some species, experienced breeders build much better nests than inexperienced breeders, suggesting that learning also plays a role.
So as often is the case, both nature and nurture seem to be involved in animal's behaviour.