Nestboxes are used by many avian biologists to study bird breeding. They are useful in that species often choose nestboxes in preference to natural sites when they have the choice. This means that if there are a lot of nestboxes in an area, it is comparatively easy to study the breeding success of (almost) an entire population. It is also much easier to count the number of eggs and young and researchers don’t have to spend long hours finding nests in the first place (although you do have to remember where you put them, which can be easier said than done – in plantations especially!).
Anne Goodenough has recently been involved in a very large study looking at patterns in bird nestbox use across Europe. This has resulted in a paper with over 50 authors from 18 different countries, the abstract of which can be viewed here: http://onlinelibrary.wiley.com/doi/10.1111/2041-210X.12160/abstract. The study examined breeding for 365 populations and nearly 80,000 individual nests. One of the study populations was at Nagshead in the Forest of Dean, Gloucestershire, which some of the current third year students visited on their first year field trip.
The study found that the nest box size and construction affected breeding success for some species – great tits, for example, had bigger clutches in bigger boxes. It also found that there were systematic differences in parameters such as nestbox size between countries. This is important to know, since studies that compare breeding performance over large spatial scales could actually be identifying trend in nestbox design rather than (or in addition to) “real” biological trends.