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.
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).
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.
Diet
Yellow-tailed Black-Cockatoos have a diverse diet.
They feed mainly on the seeds of native plants particularly in the Proteaceae family (Banksia, Hakea), while larvae of wood-boring insects (in Acacia, Casuarina) can make up a significant portion of the diet; making the Yellow-tailed Black Cockatoo unique amongst parrot species in south-eastern Australia as they can be thought of as an omnivorous cockatoo.
Proteaceae (Banksia, Hakea)
Lambertia formosa (Mountain Devil)
Wood-boring Larvae
Nectar and/or flowers are commonly eaten and seeds of introduced pine like Pinus radiata have become an important food source even if many plantations have replaced native habitat.
Yellow-tailed Black-Cockatoos consume the rich nectar of Lambertia formosa by either squeezing the base of the flower, or tipping the flower up into the beak with their head back, in what could only be described as a drinking action.
An observation and lab study in the late 1980s confirmed the species extracted fungi and slime mould from under the bark of dead trees (1). These exceptionally intelligent birds know exactly where, when and how to find the food they want, and there is still a lot to learn about them.
Juvenile Yellow-tailed Black Cockatoos in their first year (dependent on parents) will alternate between staying still and begging – often for long periods of time – and experimenting with self feeding such as with Banksia to (often clumsily) try and extract seed. Often the Banksia infructescence (in the case of B.integrifolia) will not be removed from the tree; rather the bird will attempt to extract seeds without holding it, or pull seeds out if there are open follicles.
YTBC has a long, slender bill unlike that of any other black-cockatoos, besides the Baudin’s which is longer but for different reasons. The slenderness of the YTBC bill can only be appreciated when viewed front on.
The evolution of the YTBC beak is clearly heavily adapted to their common behaviour of digging deep into wood to pull out grubs/larvae deep within branches and trunks of hardwood species like Acacia and Casuarina.
YTBC are adept at locating standalone individual Banksia trees planted in suburban gardens, to which they will often return annually.
Most Banksia species in the south east provide a year-round food source for Yellow-tailed Black-Cockatoos, as their seed-containing follicles mostly remain closed for long periods of time, until fire or death of part of all of the plant stimulates the opening of the follicles and release of the seeds.
An exception to this is Banksia integrifolia (coast banksia) which does not hold on to its seed. When the seed is mature the follicles soon open for seed release, with no seed being held on this plant at the end of each season. This usually occurs in the late spring into early to mid-summer. Yellow-tailed Black-Cockatoos have an obvious instinctive pattern of behaviour to descend on coastal areas during this time specifically to access the seeds of B.integrifolia, although they will also consume some other foods while in the area (e.g. larvae).
Some years I have noted some arriving earlier in the season and consuming the flowers of B.integrifolia before any infructescences have formed.
Once the concentration of B.integrifolia seed pods have diminished to the point where there’s not enough to sustain the flock or warrant their effort, the number of birds reduces and flocks eventually move on.
This is a widespread species in eastern Australia occuring in many different habitat types from the mountains to the coastal fringe and importantly, they are capable of travelling vast distances. Little to nothing is known about their nesting and movement habits in NSW. Regardless of where they are, the Yellow-tailed Black Cockatoo seeks out specific types of inverterbrates in the form of wood-boring larvae. At times it’s possible that these larvae are not just a supplement to the diet, but could be a dominant part of the diet. This species has a powerful beak that has evolved to carry out this very task in a methodical and expert manner.(2)
References
1. Fungal feeding by Yellow-tailed Black-Cockatoo
2. Cockatoos, Matt Cameron CSIRO Publishing 2007
Breeding
It is well known that females will usually lay two eggs, but only one chick will survive. It is not known if or how often a pair may in fact successfully fledge two chicks. From many observations over the years, I’ve never seen a pair with more than one dependent young. Western Australian black cockatoo expert Rick Dawson estimates that Carnaby’s Black Cockatoos will fledge two young 5-8% of the time.
The second egg is generally smaller in size and weight compared to the first egg. Usually only one chick survives despite two eggs often being laid. The second and smaller chick is often out-competed by its older sibling. This is a common reproductive strategy for many Australian parrots where the second egg functions as an “insurance policy” if the first egg fails (1) .
During September 2021 a pair of Yellow-tailed Black-Cockatoos appeared to have two dependent young. Only four birds were present for approximately 30 minutes, with the following observations being made:
- The appearance of both young birds noted and photographed (one male with pink eye ring in development which is not unheard of in first year males, and the other likely female) and both birds vocalising and behaving as first year YTBC chicks do (e.g. clumsily feeding on Banksia, body position and posture). The other two birds were clearly an adult male and female.
The only other explanations would be if one young was last year’s chick; however the behaviour of either bird didn’t fit this. Alternatively, if one unrelated juvenile has somehow lost its parents and has latched on to another family; there is no evidence of this ever occuring though.
References
1. Way, S. L. and van Weenen, J. (2008) Eyre Peninsula Yellow-tailed Black-Cockato (Calyptorhynchus funereus whitei) Regional Recovery Plan. Department for Environment and Heritage, South Australia.