This is a simple puzzle requiring the solver to sort the listed words into four named categories. But beware – where a word has more than one meaning, it is possible to focus on the wrong meaning and overlook that it belongs in a certain category. It is also possible to too hastily place a word into a category, such as placing 'swan' into the category 'songbirds' simply because it is a bird (although it is not a songbird).
A version of this puzzle was featured in a BBC Four gameshow called 'Only Connect'. At the time of writing, a free-to-play quiz was available on the website.
All but two of the listed words belong in one of the four categories. Put these two words together to form a word or phrase.