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Today on Animal Fact Files we’re discussing jacobins. We're not talking about the cuckoo, or the fancy feathered pigeon, or a member of a radical club from the french revolution– we’re talking about the hummingbird. How these hummers got this confusing common name is unknown to us– if you know, tell us in the comments! There are two jacobin hummingbird species, and they're both named for their appearance: there's the white-necked jacobin and the black jacobin. As you might be able to guess, the black jacobin is largely black but has a white underside to its tail. The white-necked jacobin is blue across its back and has a white spot on the back of its head. Its underside is white. Most of the adult females of the white-necked jacobin species have green back feathers and a speckled chest and belly, however, about 20% of the adult females in this species look indistinguishable from the males!

Many birds display sexual dimorphism– the males and females look different from one another. Although this is true for the white-necked jacobin, it's not entirely true. Some of the females of this species look just like the males. It's not fully understood why this occurs, however, it has been observed that male colored females experience less aggression from their male conspecifics while feeding. Essentially, the females that look like males don't get harassed by males nearly as much as the females that don't look like males, so the male-look-alike females have easier access to food. It's generally believed that in birds that display sexual dimorphism, the females are often more dull because it helps them blend in with the environment while they incubate their eggs. For this reason, it's also believed that the male-colored female white-necked jacobins probably have less nesting success than the other 80% of the female population.

White-necked jacobins and black jacobins both move around their territory, but the extent of their movement patterns are not well understood. Black jacobins are considered migratory, with distinct areas in which they breed as well as places they do not. These birds range from southern Brazil and Paraguay to Uruguay and northern Argentina. White-necked jacobins live further North ranging from southern Mexico to Brazil and Bolivia, spanning from coast to coast across the continent. Both species live in forested habitats including plantations and gardens. They're often observed at edge habitats where they have easy access to both flowers and insects. It's not uncommon for them to frequent river edges as well.

Jacobins average 4 to 5 inches (10-13 cm) in length with the black jacobins appearing slightly larger. Like most hummingbirds, jacobins eat flower nectar to fuel their high speed lifestyle. This is an energy rich food! They most frequently gather nectar from flowers that grow in the tree canopy. They're aggressive around food, and will drive both conspecifics and other hummingbird species away, although they're generally not listed as territorial. They move around and don't focus on a single patch of flowers for long periods of time. These birds also eat insects which they'll catch while flying through the air. Jacobins often fly over water to grab a flying insect or pick a spider right out of its web! Insects are an especially important food source for their growing young.

It's typically the most beneficial to have babies during the most food rich time of the year, and jacobins follow this logic. When insects are most abundant, these birds nest. The female constructs the nest with gathered materials such as down and even cobwebs! Jacobin nests are observed in close proximity to streams and other waterways which may be because this is an easy location to gather food for the young. Overall very little is known about jacobin reproduction, however, like other hummingbirds, the jacobin chicks need lots of protein to grow. They can't subsist on nectar alone, and for their first few weeks of life their mother will supply them with a healthy amount of protein-rich arthropods gathered from the nearby stream. The less she has to fly to find food, the more energy she can spend on actually catching it, so nesting near a water source is beneficial!

Jacobins produce high pitched squeaks. In fact, the black jacobin has been observed making calls that are outside the known hearing range of birds! Why they do this is still a mystery. Here's an example of what a jacobin sounds like: (high pitched squeaks).

For more facts on jacobins, check out the links below. Give a thumbs up if you learned something new today. Thank you to our Patrons SpikeSpiegel93, Dad, and everyone else for their support of this channel! And thank you for watching Animal Fact Files!