Monday, January 31, 2011

Parakeet roost count

Pacific Parakeets
Last Saturday, I and other members of the Salvadoran branch of Partners in Flight, a local association of bird observers and bird conservationists, counted the parakeets roosting on the grounds of the Universidad Centroamericana José Simeon Cañas ("UCA") in Antiguo Cuscatlán, a neighborhood in San Salvador, the capital of El Salvador.

This roost is visited primarily by two Aratinga species - Pacific Parakeet and Red-throated Parakeet. The former roosts there in the hundreds and hundreds, while the latter is usually encountered as scattered individuals here and there for a total of 10-20 birds. Because the two species are very similar and difficult to distinguish in flight, it is likely that the actual number of Red-throated Parakeets roosting there is a little higher, several tens perhaps.

Red-throated Parakeets
Our count Saturday reached 1,150 Green Parakeets, among which we were able to find at least 12 Red-throated Parakeets. Simultaneously, other observers covered areas nearby, where in the past these parakeets have also roosted. However, it turned out that those roosts were not currently used and that all birds congregated in the main roost in the UCA.

A guard at the UCA told us that he has seen larger species - parrots - among the parakeets. We did not detect any Amazona parrots using the roost, although we did see two pairs of Amazona sp. fly high over the roost a little after 6 PM, when most parakeets had already arrived at our roost. When we arrived at the roost site, we saw a pair of Orange-chinned Parakeets, a much smaller species that does not roost in large groups, but is commonly found throughout the city.

Red-throated Parakeets grooming each other
Within the cacophony of the roost at large, most parakeets are paired off and can be seen perched in duos grooming each other, a very romantic sight.

As I said in the previous post, count results will be shared with parrot researchers at the universities of Leiden and Heidelberg.

Note that taxonomy of the Aratinga genus is still somewhat unclear - at least to me. Some sources consider strenua to be a subspecies of Aratinga holochlora (Green Parakeet), others claim it's a species in its own right (Pacific Parakeet). Some consider Aratinga rubritorquis (Red-throated Parakeet) to be its own species, others claim it is a subspecies of Aratinga holochlora.

Saturday, January 29, 2011

Pacific Parakeets

Pacific Parakeets roosting in San Salvador
I've written before about the Pacific Parakeet roost in Antiguo Cuscatlán, a neighborhood of San Salvador. Later today, Saturday 29 January, me and other birders in El Salvador are going to count the parakeets that use this roost as part of a World Parrot Count, organized by two parrot researchers from the University of Leiden (The Netherlands) and Heidelberg (Germany).

When I stumbled upon their web site, I immediately thought about the Antiguo Cuscatlán roost and how I and others could participate in this initiative. I suggested this to the local club of bird observers in El Salvador, and many people responded with enthusiasm. The ministry of environmental affairs even put out a press release, resulting in some press coverage (and more press coverage here and here)!

Several hundreds of parakeets roost here, the vast majority Pacific Parakeets, often with some Red-throated Parakeets mixed in. Roselvy and I were there a few weeks ago and saw at least 12 Red-throated Parakeets, thinking there were probably more. I hope to be able to share the results of our count here in this blog tomorrow.

Sunday, January 23, 2011

Immature hummingbirds

Green Violetear
In Reserva Biológica 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.

Saturday, January 22, 2011

The undescribed song of the Green-breasted Mountain-gem

Immature male Green-breasted Mountain-gem, 18 January 2011, Honduras
The Green-breasted Mountain-gem, a little known hummingbird from central Honduras and northwestern Nicaragua, sings a soft, scratchy rapid warble from inside dense vegetation. The song is audible only at close range (<7 m) and so far has not been formally described to science. Last month I recorded some songs of this type in Reserva Biológica Monte Uyuca, Honduras, and wrote about that in this blog. Back then, I also recorded another song that I erroneously thought was this species but turned out to be Green Violetear.

Last week, Roselvy, Vicky and I went back there for the January bird banding pulse. Hummingbirds are so abundant in Uyuca that in the breeding season - which for them is now - they can be heard more or less constantly, often more than one species at a time. In the majority of the recordings I made this week, I have Green Violetear, a tireless singer, in the background. But let's start with a recording that has only the Green-breasted Mountain-gem:

This individual is singing a couple of shorter songs.

At times, the song is augmented with a trill at the end that sounds a bit like an old telephone ringing long distance (but higher). Listen for example to this individual, who first sings a few shorter songs, and finally a longer song with that trill (and ignore the staccato chip song in the background - that's the Green Violetear):

Here's another example. First a short song, then a longer song with that trill:

I recorded these songs during net runs, and didn't have opportunity for more extensive observations. Many Green-breasted Mountain-gems have already bred, evidenced by the proportion of immatures we caught. It seemed to me there was more singing going on now than a month ago; perhaps these are males teaching their sons how to sing. (I recorded a very odd, unstable Green Violetear song that I assume was a young bird practicing.)

Here's a recording of a young male calling. The bird was perched and looked around nervously while calling; once it spread its tail. These calls are unlike the contact and feeding calls uttered by the adults:

Here's a call uttered by an adult male while perched in a small tree at a height of 2 m. These are typical calls of this species, also heard when feeding:

Compare the song of the Green-breasted Mountain-gem with that of its sister species, the Green-throated Mountain-gem. First a Green-breasted:

And now a Green-throated, recorded by Nathan Pieplow in Chiapas, Mexico:

Note how similar those songs are!

Saturday, January 15, 2011

Notable sightings in San Salvador

Fan-tailed Warbler, January 15, 2011, San Salvador
Roselvy and I went birding this afternoon in the botanical garden La Laguna, in the San Salvador neighborhood of Antiguo Cuscatlán. Easily accessible by bus, we sometimes go there to still get a little birding in when we don't really have time for trips further afield.

We did great! We found a couple of birds normally encountered in more extensive woodland, one bird that winters on the Atlantic Slope and is rare anywhere in El Salvador, and one bird that is normally found at higher elevations.

Fan-tailed Warbler belongs to the first category. A habitat specialist normally found near ravines, where it hops around on the ground looking for ants, its principal food source.

Orange-billed Nightingale-Thrush January 15, 2011, San Salvador

Orange-billed Nightingale-thrush also falls into that first category. We had no idea this bird can be seen in the city of San Salvador.

Hooded Warbler, January 15, 2011, San Salvador

Hooded Warbler is an Atlantic Slope winter visitor to the region that is rare in El Salvador, situated on the Pacific Slope.

Another surprise was Black-throated Green Warbler, a common winter visitor here at higher elevations in pine-oak, but probably irregular in the city.

Thursday, January 13, 2011

The variable song of the White-eared Hummingbird

female White-eared Hummingbird, January 2011, Montecristo, El Salvador
White-eared Hummingbird is one of the most common hummingbirds of Mexican and northern Central American pine-oak forests, a bird highly characteristic of its habitat. Having spent considerable time in that habitat, I thought I knew it quite well.

But it turns out I hardly know it at all.

For example, I thought I knew its vocalizations, both song and call. I've spent the last four winters in Central American pine-oak forests looking for wintering Golden-cheeked Warblers, and saw and heard this hummingbird all the time.

But a couple of days ago, while banding birds at the pine-oak banding station in Montecristo national park, El Salvador, I recorded a hummingbird song that I was not familiar with. I knew the hard, metallic chip that males produce constantly this time of year. But the insect-like chirp that I recorded on Tuesday is very different. Here it is:

Here's another, shorter fragment of the same bird, singing the same song.

And here's a short fragment (of presumably the same bird) with rather typical feeding calls. These I was already familiar with.

Alexander Skutch, in his fascinating book on birds of the region called Trogons, Laughing Falcons, and Other Neotropical Birds, writes about White-eared Hummingbird singing leks he studied in Guatemala. He notes something that was new to me, but immediately 'clicked' when I read it. I'll quote at length:

Perhaps the most typical note of the male White-eared Hummingbird is a low, clear tink tink tink, sounding like the chiming of a small silver bell. This was the note that I first heard and prefer to remember. Some individuals toll their tiny bells very rapidly, others more slowly and deliberately. But as I became familiar with more and more White-ears, scattered over miles of mountainside, I was surprised by the variance of their voices. Many individuals consistently uttered notes so different from the usual clear tinkle that I did not recognize them as belonging to White-ears until I laboriously stalked the birds and watched them calling. These notes were dull and flat, devoid of the clear timbre characteristic of the species, or high and squeaky, or low and melancholy. One White-ear that I often visited repeated rapidly a harsh, metallic click, a buzz almost painful to hear.

Equally unexpected was my discovery that all members of an assembly sang in much the same way but differently from those in other assemblies.  If one bird of a group repeated a silvery tinkle, his neighbors would be found to do the same; if I was attracted to an assembly by chirping notes, this was the prevailing tune.

from Alexander F. Skutch, Trogons, Laughing Falcons, and Other Neotropical Birds, 1999, Texas A&M University Press, College Station, Texas, USA.

The insect-like song that I recorded is not described in Howell's guide to the region, nor in Sibley's or Kaufman's guides to North American birds. In fact, apart from Skutch's perceptive observations quoted above, most bird guides tend to give succinct, seemingly complete descriptions of its vocalizations. To my ears, none of the other White-eared Hummingbird vocalizations represented in xeno-canto at the time of writing sound like my bird. And although only a single bird can be heard in my recordings, I sometimes heard another one there, duetting with a similar song.