About Immatures
About immatures
The immature Bare-necked Umbrellabird of both sexes closely resemble an adult female, showing a deep brown eye, a small crest, small bare red skin patch on front of neck and black legs and feet. Maxilla is black with the lower mandible lighter in color.
In the field, a first-year male is next to impossible to sex and is often misidentified as a female. Bare-necked Umbrellabirds appear to have a very slow molt cycle and may take many months to complete. All birds we have captured for banding have not shown any sign of molt in process during the months of February to early June. If it were not for the color leg bands we place on chicks before fledging, we would never be able to determine the sex of the one year old individuals that have returned to the research area from the previous year. A first-year male has the size, body and head shape of a female. The first-year male does however show a very small naked fleshy red patch at the lower throat / upper chest area that will one day form into a vocal sac. But do not let that red patch sway your conclusion from female to male. In the early days of our observation experiences, we once followed a young male all day on his foraging expeditions, only to realize later it was a female. Females can show their naked fleshy red patch along the front of the neck as well, especially while sallying for fruits or foraging with neck outstretched while reaching for food items above their head.
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Only in the immature males second year could we confirm with 100% certainty of the sex through field observations. By this time immature males have a small crest forming which is visible in the field (as does the female so be careful making your determination based on just the crest alone). And like the female, an immature male crest cannot be manipulated to fully cover the length of the bill like that of an adult male. Luckily, by year two, an immature male is showing a small but obvious red vocal sac large enough to not be confused with a female. Some two-year old males we have seen had a black line of feathers that cut straight up from bottom to top of the vocal sac dividing it into two separate parts. These feathers slowly give way and the sac eventually becomes totally naked. At this age, you may even find the emerging vocal sac adorned with a few small feathers protruding from the now obvious fleshy appendage that will one day display his fully formed tassel. By the age of three, he is surely looking like a handsome male, but even the most enthusiastic three-year old male struggles to impress any female with his under-developed vocal sac and feeble attempt at a display call.
Our observations of surviving chicks support our theory that young birds often return to their birth place years after they depart the nest. We have spotted young males visiting both lek and nest sites up to three years after they have fledged (click on our nesting and lekking tabs for more details).
Juvenile vs Immature
A juvenile bird is a young bird that has not yet entered into its first molt of new feathers in the process of maturing into adulthood. The first molt can happen within weeks of hatching in some birds, but can take many months in larger birds such as raptors.
Any young bird having new feathers after its first molt but not yet reaching the full adult stage of maturity is considered an immature.
