Sunday, January 23, 2011

Immature hummingbirds

Green Violetear
In Reserva Biol├│gica Monte Uyuca (Honduras), where Roselvy, Vicky and I banded last week, five species of hummingbirds are common: Green-breasted Mountain-gem, Green Violetear, White-eared Hummingbird, Magnificent Hummingbird, and Azure-crowned Hummingbird. They've all recently bred or are still breeding, for we caught immatures of each species, as well as an adult female Green-breasted Mountain-gem with an egg in her oviduct.

Let's take a look at these immature plumages. Few field guides illustrate them, although the Howell & Webb guide to the region does routinely describe them, if not in very much detail. Generally, younger birds are characterized by buffy feather tips on the upper and sometimes under parts. In the hand, presence of bill striations (fine corrugations along the side of the maxilla) indicates a younger individual. (Double clicking on these photos will reveal them in some cases.)

The top bird is a young Green Violetear. It will lose those buffy tips on the head and back through a first prebasic molt during its first life year. Those dusky underparts will become metallic green.

Azure-crowned Hummingbird
 Here's a young Azure-crowned Hummingbird. This bird too has extensive buffy fringes on the head and upper parts. In this species, the buffy tips of younger birds even extend to the tertials.

Magnificent Hummingbird
Immature Magnificent Hummingbird, with buffy (upper side) or whitish (under side) feather tips all over, again including the tertials.

White-eared Hummingbird
A tiny White-eared Hummingbird, weighed only 3 grams (the adults are tiny also, of course). Here we see buffy tips to the head and lower back feathers.

White-eared Hummingbird
Here's another look at the same bird, showing those buffy tips to the lower back feathers. Adults have all-green backs.

Both sexes of Green-breasted Mountain-gem show dusky greenish throat feathers, which they quickly replace with (usually buff-tinged) whitish feathers in the case of the female, or bright green feathers with white borders in the case of the male.

Green-breasted Mountain-gem

Here's a female. Note the buffy tips on the head and back, and the dark throat feathers, both characters associated with immatures in this species.

Green-breasted Mountain-gem
And here's a male. This individual shows a distinct rufous spot over the eye, found in many but not all young individuals of both sexes in this species. A few basic (post-juvenal) throat feathers have already grown in.

Green-breasted Mountain-gem
Young Green-breasted Mountain-gems too show rufous tips to the feathers of the lower back. In this species, males of all ages show dark upper tail coverts, a character lacking in females.

1 comment:

lisita55 said...

Ah! what a beautiful post! you made my morning! Wonderful pics, thorough, comprehensive descriptions, interesting facts.... Thank you, thank you, thank you!