We are all aware that there are some truly stunning birds out there: majestic eagles and vultures, vibrant parrots and hummingbirds, eye-catching cranes and pelicans. But those of us who spend a lot of time contemplating the nature of bird diversity, whether as bird-watchers or ornithologists, will soon admit that the greater proportion of this diversity is composed of what are affectionately or not-so-affectionately referred to as Little Brown Jobs. In particular, the tyrant flycatchers or Tyrannidae of the Americas are one family of birds that is notorious for including some of the littlest, the brownest, and the jobbiest.
Elaenia is a genus of about twenty or so species of tyrannid found in Central and South America (Sibley & Monroe, 1990, listed eighteen, but phylogenetic studies suggest that some of these should be divided into more than one species—Rheindt et al. 2009). The name 'elaenia' does double service for these guys as both genus and vernacular name, though the members of some related genera are also labelled in the vernacular as 'elaenias'. As a result, Ridgely & Tudor (2009), without a trace of apparent irony, referred to the species of this genus as 'Elaenia elaenias'.
The various species of Elaenia elaenias are notoriously difficult to distinguish, and none are particularly eye-catching. They are mostly greenish, though the slaty elaenia Elaenia strepera is dark grey, and the brownish elaenia E. pelzelni is (surprisingly) brown. Underparts may be white, or they may be yellow. One species in particular is labelled as the yellow-bellied elaenia E. flavogaster, but in this case it is not any more strikingly yellow than a number of other species, leading one to suspect whether its vernacular name is any sort of moral judgement. A number of species have some degree of white streak on the crown, and some have a small crest of feathers (the mottle-backed elaenia E. gigas has a well-developed, bifurcated crest). Elaenias are best distinguished by their calls, but that of course requires the bird in question to be calling.
Though members of the tyrant flycatcher family in both affinities and appearance, elaenias consume a fair proportion of fruit as well as insects. In at least some species, fruit make up by far the greater part of the diet (Marini & Cavalcanti 1998). Different species often have different preferred habitats, and the relationship between habitat and phylogeny was examined by Rheindt et al. (2008). Two savannah-dwelling species, the plain-crested elaenia Elaenia cristata and the rufous-crowned elaenia E. ruficeps, appear to be the sister clade to the remaining species that mostly inhabit riparian habitats or montane and temperate forests (Elaenia species are largely absent from lowland tropical forest). The forest species fall into two clades nested among the riparian species. The great elaenia E. dayi, which happens to be the largest Elaenia species by a noticeable margin, inhabits the stunted montane forests of the south Venezuelan tepuis (if you've seen the film Up, this is the habitat in which that film is mostly set). Migratory habits, on the other hand, are less correlated with phylogeny than habitat preferences. A number of Elaenia species migrate between temperate breeding grounds and tropical wintering grounds, but migratory species may be closely related to sedentary species that inhabit the tropics all year round. Indeed, some species are mostly sedentary but have somewhat migratory populations in more temperate parts of their range.
Marini, M. Â., & R. B. Cavalcanti. 1998. Frugivory by Elaenia flycatchers. Hornero 15: 47-50.
Rheindt, F. E., L. Christidis & J. A. Norman. 2008. Habitat shifts in the evolutionary history of a Neotropical flycatcher lineage from forest and open landscapes. BMC Evolutionary Biology 8: 1193.
Rheindt, F. E., L. Christidis & J. A. Norman. 2009. Genetic introgression, incomplete lineage sorting and faulty taxonomy create multiple cases of polyphyly in a montane clade of tyrant-ﬂycatchers (Elaenia, Tyrannidae). Zoologica Scripta 38: 143-153.
Ridgely, R. S., & G. Tudor. 2009. Field Guide to the Songbirds of South America: The Passerines. University of Texas Press.
Sibley, C. G., & B. L. Monroe Jr. 1990. Distribution and Taxonomy of Birds of the World. Yale University Press.