What is "little brown job"

n. (context birdwatching English) One of any number of small, nondescript, sparrow-like bird species that are very hard to tell apart.

Little brown job or LBJ is an informal name commonly used by birders for any of the large number of species of small brown passerine birds, many of which are notoriously difficult to distinguish. This is especially true for females, which lack much of the coloring present in males.