Readers’ wildlife photos

Send in your photos if you got ’em!

We have a batch of lovely hummingbird photos today sent in by Ephraim Heller, including a hummer in her nest. His captions and IDs are indented, and you can enlarge the photos by clicking on them.

On my February visit to Trinidad and Tobago I managed to photograph 13 of the 18 hummingbirds that are sometimes present on the islands. A previous post was devoted entirely to my new favorite bird, the tufted coquette. Today’s post contains photos of six other species; a subsequent post will cover the remainder. The species that I did not photograph either do not visit feeders or are only present seasonally in the country.

Trinidad and Tobago sits at the junction of South America and the Caribbean, and its unusual diversity of hummingbird species is due to its recent geological separation from the Venezuelan coast and the diversity of habitats it retains. Both Trinidad and Tobago are fragments of the South American continental shelf that were once connected to the mainland and later became isolated as sea levels and tectonics changed. Trinidad was connected to South America via a land bridge during the last glacial maximum, 10,000-12,000 years ago. The white-chested emerald population restricted to Trinidad and the white-tailed sabrewing restricted to Tobago show that measurable biological divergence can occur over relatively short timescales once island populations are isolated.

Hermits (subfamily Phaethornithinae) diverged from all other hummingbirds early enough in the family’s evolutionary history that they are sometimes described as a parallel radiation. They share several features that distinguish them from typical hummingbirds: bills that are long and strongly curved (matching the curved tubular flowers they prefer, particularly Heliconia), plumage that is brown or green rather than iridescent, and a foraging strategy — trap-lining — in which each individual follows a memorized route through the forest, visiting widely spaced flowers in sequence rather than defending a single patch. Because trap-liners visit many individual plants across a large area, they tend to carry pollen between plants that are far apart, making them important cross-pollinators over distances that territorial hummingbirds rarely cover. Male hermits do not defend territories at all; instead, they gather in loose groups (leks), where each male sings from a fixed perch to attract females. Females select mates and then nest and raise young entirely on their own.

Green Hermit (Phaethornis guy):

Little Hermit (Phaethornis longuemareus):

Rufous-breasted Hermit (Glaucis hirsutus):

The rufous-breasted hermit is the primary and perhaps the unique pollinator of the deer meat (Centropogon cornutus) flower:

Here is a rufous-breasted hermit on its nest, built under the leaf of a Heliconius:

Now moving on from the hermits (subfamily Phaethornithinae), the rest of my photos are of species of typical hummingbirds (subfamily Trochilinae).

The white-necked jacobin (Florisuga mellivora) has been studied extensively because a proportion of adult females look like males. In most hummingbirds, the two sexes are clearly different in appearance, with males being more colorful. In the jacobin, all juveniles of both sexes bear the same ornamented, male-like plumage. As they mature, about 80% of females change to the typical muted female pattern, but roughly 20% retain the male-like appearance into adulthood. The leading hypothesis is that this reduces harassment by territorial males: for reasons I do not understand, male jacobins tend to aggressively harass and drive off female jacobins during feeding, while ignoring other males.  What makes this interesting for biologists is that it demonstrates that colorful, male-like ornamentation in females can arise through means other than sexual selection.

[JAC: I bet some chowderhead would say this bird has three sexes because of the dimorphism in females]

Male pattern white-necked jacobin:

Female pattern white-necked jacobin:

Long-billed Starthroat (Heliomaster longirostris):

The white-tailed sabrewing (Campylopterus ensipennis) occurs only on Tobago and in a small area of northeastern Venezuela. When Hurricane Flora hit Tobago in September 1963, it destroyed much of the Main Ridge Forest Reserve; the sabrewing population appeared to have been eliminated entirely and the species was presumed locally extinct for eleven years, until individuals were confirmed to have survived in 1974. Current estimates for the Tobago population range from several hundred to over 1,000 birds.

White-tailed Sabrewing male:

White-tailed Sabrewing female: