Yellow-tailed Black-Cockatoo Age & Sex Identification

Information relates to the nominate subspecies Calyptorhynchus funereus funereus

Age

Once females reach their second year, they are virtually indistinguishable from mature females.

Identifying immature male birds (approx. 4 years and under) is achievable – but knowing his exact age is not straightforward.

There’s no template that males follow in developing their pink eye ring and dark beak.

Over years of observing and photographing the species, it is clear that individual males will develop these two distinguishable physical traits at varying times in their early years.

Some males start to develop a pink eye ring while still in their first year, while still dependent on the parents.

Others will start to develop a dark upper mandible before any skin around the eye starts to turn pink.

Juveniles (chicks) – First year dependent YTBC identification

Determining a bird of under one year old (still dependent on parents) is the easiest of all and is best done – at least from a distance – through behavioural observations.

First year juvenile (dependent) YTBC are almost always very easy to identify through physical features as well:

Either a smooth white beak, or upper bill with black colouring throughout – this is not the same dark beak that later forms in males, but rather the chick’s beak developing. Many YTBC (and White-tailed black cockatoo) chicks develop blackness on the upper mandible in the nest. This will fade to white throughout their first year regardless of sex.

The beak surface of a first year juvenile is notably smoother than that of older birds. Black cockatoos (and all other cockatoos), besides juveniles, have an obvious roughness and flaking to the bill, as it constantly sheds layers. The smooth mandibles of a juvenile/first year YTBC is a clear indication of their age.
Even when the feathers are raised to cover the entire lower mandible and much of the upper, this physical trait is obvious. There can be a small amount of flaking when the chick still has black markings on the top beak.

First year juvenile with smooth white bill perched in the hunched position

Dependent juvenile (first year) with dark upper manible

Dependent first year juvenile. This bird appears to have a larger cheek patch indicating potential female

Most obviously, if a bird is begging or behaving as this species otherwise does during their first year of life, whilst they are still dependent on the parents, there’s no doubt it is a chick under one year old.

Beyond the one year mark, things become trickier with females. The larger cheek patch is the most notable feature to indicate a female, but it is not always easy to determine without a comparison male nearby, and depending on the direction of light and the way the bird is positioning the head feathers. A bird with a large cheek patch and no sign of beak darkening or pink eye ring (more on this later though), and in the absence of dependent juvenile behaviour, can be safely assumed female of 2 years or older. There’s no way of knowing whether she is in fact 2, or 22, or 52.

In White-tailed Black Cockatoos (specifically the highly studied Carnaby’s Cockatoo), researchers are able to sex chicks in the nest reliably from the size and colouring of the cheek patch, and this is confirmed through DNA testing. It can be inferred that this should, in theory, be possible with YTBC as well. Holding a nestling in the hand provides ease of view, compared with viewing a bird in the wild where a myriad of factors can influence the appearance of a cheek patch from ground view or in photos. As shown in several photos below, the appearance of the cheek patch in YTBC doesn’t always provide a clear explanation – but the variations caused by view/light/feather position etc may be the cause of questioning, rather than the cheek patch itself which would likely provide a clear answer if the bird was viewed in perfect conditions and position.

The window of age identification extends a bit more in males. Again the small amount of literature which mostly comes from the now very old and sparse HANZAB species profile states that males are fully developed by 3 to 4 years, this includes the pink eye ring and darkened mandibles.

The changing of the lower mandible to a dark grey colour is the last development of a male. However: it is possible that some males never develop a darkened lower mandible, or develop it much later in life than is assumed (i.e not necessarily by four years of age).

Immature male. Upper mandible darkening and pink eye ring developing concurrently

Usually the top mandible will be fully dark while the lower is still bone coloured. Due to the number of males I see in this state – dark top beak and light lower beak – and the fact many of these birds are fathers – raises questions about the development of these birds.

HANZAB states that sexual maturity is reached at 4-6 years. This implies birds don’t breed until that age. Therefore, either the bill takes much longer to fully darken than is thought, or birds are breeding at a younger age than the literature states. As I have seen males with both upper and lower mandible light coloured, with dependent young, I believe the birds (males at least) can and do breed at an age of 2-3 years old. Of course, it is impossible to visually estimate the age of any female with dependent young.

In any case, observing a male that is in the transitional stage of either a pinkening of the eye ring or darkening of the bill allows a virtual certainty that he is under four years of age. Why is this important? Looking at as many individuals as possible in a flock and taking note of how many young males are present – along with new juveniles – provides a very general (not comprehensive as it does not include females) indication of breeding successes of the past few years. For a long lived, slow breeding species this is one of the most important metrics when it comes to their conservation. If most birds in a flock are old, the species’ conservation status becomes even more perilous.

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