"Sarah Paaaalin! Sarah Paaaalin!" Squealing his song, MBA (Mauve-Blue-Azul) perches in his territory on lek six. Like other Little Hermit Hummingbirds, his song perch is less than two feet off the ground. Save for a yellow gape (the inside of his bill) and the white tips of his tail feathers, which he bobs incessantly, he blends with the forest. Up close, Little Hermits have a subdued beauty; slightly iridescent green-brown feathers, a dark brown mask over the eye, and a long diamond-shaped tail. From afar, the details fade. And though definitely still beautiful, something about the hunched posture, decurved bill, and drab coloration brews a jizz that's more adorably grumpy than anything. If he's average, he weighs around 2.5 to 3 grams...about the same as a US penny.
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| VRN (maybe). First capture of the season and main subject of a fantastical windchime/desert/aquatic hummingbird dream. |
MBA's neighbor to the south, OAP (Orange-Azul-Purple), is visually identical (in our eyes), but he's singing "You'readouchebag! You'readouchebag!", a sped up version of MBA's song. Note: most of the dialects had already been given mnemonics during previous field seasons, I just thought this pair was an amusing example. On other leks ( a lek is an area where the males of a species go to display and/or sing for the females) and within leks, groups of hermits are singing very different dialects. Julian would do a better job at explaining this, but here goes. This song business is an energy expensive endeavor. Energy expensive on an individual basis because males will spend a great deal of their youth
learning to sing, practicing on and off the lek, then establishing a territory, either by taking over a pre-existing one or by setting up shop on the outskirts of a lek, and then maintaining their tiny kingdom through adulthood. As adults, they are seemingly bound to the lek; breaking for food and nighttime roosting, but otherwise devoting most of the daylight hours during the breeding season to their manly Hermit duties. Evolutionarily, song-learning is costly because of the sheer amount of brain structure needed to be developed and devoted to that arena. All this from a bird in a taxonomic order not known for its singing prowess!
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| Back tag: Affixed with crazy glue, and created with melted down pearler beads and our superb crafting skills. This one RYP (Red-Yellow-Purple). Photo taken by Julian Kapoor. |
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Another bird from the ridge lek. A lot went into catching these ridge birds, including a mostly in the dark hike up to a cloud forest, overnight camp, and scramble down the next night. Awesome! Photo taken by Julian Kapoor.
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Julian's Ph. D. work with the Little Hermit, the reason Rachel and I are in Trinidad, is an attempt at deducing 'why?'. What's the point of different groups of the same species, on the same lek, singing different songs? Are they imitating a dominant male of that song group? Is it kinship based? Are certain song characteristics inherently more attractive to females? Could it be due to the nature of sound itself...traveling and reverberating differently in varying environments? To answer these questions, he's doing a number of things. The information we gather during the field season falls into three main categories: Behavioral observations, genetic sampling, and audio recording.
The nitty-gritty of all this means there's a lot of work to do, especially with the genetic sampling category. We need to catch every male from at least five different leks on the field site. Some kept their tags and therefore already have had samples taken for genetics. Those guys are home free. We sample at a number of other leks farther from the main site too, but they have slightly lower priority. Each of the males that we capture are fitted with a colored back tag and a leg tag attached to a uniquely numbered band. The back tag generally falls off by the end of the season as the bird molts, but is very useful for identifying flying birds. The leg tag will hopefully stay for future seasons, though sometimes is rendered unreadable due to fading, or dirt or cobwebs. For genetic analysis, Julian plucks a few pin feathers or collects a drop of blood from the bird's foot.
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| An individually created, 5.1mm long, numbered hummingbird band (on my middle finger). |
So that's all for the male hermits...what about the ladies? One of the main things we focused on this season was attempting to radio-tag females in order to look at the feasibility of tracking them back to nests (more on radio tagging later!!) They don't visit the lek frequently enough to catch them there, like the males, so we spend a surprising amount of time watching for foragers. Thats a short way of saying we go back to places we've heard or seen hermits, or even just go to patches of the species of flowers that they like....and wait. Little hermits are 'trapline' feeders, i.e. they follow the same foraging route repeatedly, sometimes even visiting the exact same flower, throughout the course of the day or week, or longer. If we see a bird foraging on one of our watches, there's a good chance it will be back within an hour. Catching birds this way is HARD. And our criteria is very specific. Ideally we want adult, actively nesting, females. Using bill striations, the adult thing isn't difficult to figure out. Determining sex is trickier. There is slight sexual dimorphism, with females weighing a bit more and also usually having a thicker tarsus than males. Supposedly the male sports a darker 'goatee' but this wasn't something I could really see. We rely heavily on the process of elimination. If all of the adult male birds in our study area have been color-tagged...who's left? The last thing, 'actively nesting', is mostly a cross-your-fingers sort of deal.
Behavioral observations, although they comprised the bulk of our time, are simpler to explain. In order to figure out how much time birds are spending on the lek, and what they're doing during this time, we watch and record everything. There's more to it than that, but this is already getting bulky (high fives and wow(!) to those still reading). Plus, I'm thinking of doing a (slightly risqué) post on the one copulation I saw, during a watch, so that would pretty much cover that... Lastly is audio recording data. Over the course of the season we record every bird on our three core leks. On the other leks, we try to get at least one recording from each song group. Sometimes recording is quick and easy, and other times it's painfully slow and fraught with equipment woes. Elaborations to come!