Good morning, friends. I didn’t hear back from Pa Killsock in time to take his suggestion, so we’re back to my stash of tropical birds from the Americas. This week’s bird is the white-necked Jacobin. The name comes from the male’s distinctive blue cowl, which naturalists thought looked like that of Dominican friars, called Jacobins in French. Females and juveniles have a delightful iridescent scalloped pattern, although some females look like males once they are mature. Like a lot of the birds we have been covering, its range extends from southern Mexico down through central and south America, terminating in Brazil and Bolivia. It is also present on Trinidad and has been found as a vagrant in Curacao and Aruba. These birds are considered medium sized examples of a hummingbird, which means they are still tiny. They are 11 to 12 cm (4.3 to 4.7 in) long and weigh in at a hefty .4 to 9.0 g (0.26 to 0.32 oz) for males and 6.0 to 9.2 g (0.21 to 0.32 oz) for females. The females have a lower bottom of the range, but a higher top end.
The Jacobin feeds on nectar of trees, shrubs, and the flowers of members of the genus heliconia. Heliconia includes 194 different tropical plants, nearly all of which are present in the Americas. It also feeds on the flowers of epiphytes, which are plants that live on other plants, like an orchid, for example. We have encountered this class of plants before, possibly in an another header about hummingbirds. Definitely in a little clay pot in my living room, but I digress. In a first for hummingbirds we have learned about, at least as far as I remember, the white-necked Jacobin eats insects, which it catches on the wing or sallying from a perch. The idea of this tiny, shiny bird being a killer is pretty funny. I don’t associate hummingbirds with deadly mayhem, but here we are.
These hummingbirds prefer tall trees and the edges of forests, including gallery forests, formed along the banks of rivers or wetlands in areas which are otherwise arid. They will also live in coffee and cacao plantations as well as so called secondary forests, which are forests that regrow after being disturbed by logging, farming or an equally severe natural occurrence. Secondary forests are characterized by trees which are closer together than in an old growth forest, as well as less undergrowth. I’m just guessing here, but denser trees provide more places to nest and hide, and less undergrowth might allow more flowers to grow, as opposed to dense, brambly undergrowth which can survive the dimmer environment of an older forest. The Jacobin hummingbird may migrate within its range as flowers bloom, but data are sparse and this is uncertain. The bird is rated as “of least concern” by the IUCN. It is fairly common within its very large range, and there does not appear to be any indication that the population is dropping.
Finally, my favorite thing I learned this week is that white-necked Jacobin chicks may have evolved to look and behave like venomous caterpillars. Mimicry of dangerous animals as a defense mechanism is fairly common in the animal kingdom, but it is usually in the form of acting or looking like something more closely related. Non-venomous snakes may mimic the scale patters of venomous ones, lots of flying insects strive to be perceived as wasps, etc. In this case the chick not only looks like a venomous member of a very different animal group, but scientists saw it bob its head and present “spines,” (actually feathers, of course) exactly as a venomous caterpillar would. Scientists observed the chick doing this while its mother was away, and it succeeded in dissuading a wasp from taking a closer look.
Be good to yourselves and others. Remember, rest is not a reward. Don’t threaten Mayor McSquirrel no matter how forehead-slappingly stupid it gets out there.
Links: https://tinyurl.com/bd4edc4z,
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