Tony Silva NEWS: Cockatoos aggression – possible causes and solutions. PART I

March 4th, 2015 | by Tony Silva
Tony Silva NEWS: Cockatoos aggression – possible causes and solutions. PART I
Tony Silva NEWS
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Read also the second part of this article:

Tony Silva NEWS: Cockatoos aggression – possible causes and solutions. PART II

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My avicultural career spans more than four decades. During this time, I have kept and bred a huge array of species, many of which have disappeared from aviculture. I have had many successes. During these more than 40 years of keeping parrots, one group has proved more enigmatic than the others: the cockatoos. They are exceptionally intelligent, hardy and complex. I have tried again and again to understand why some cockatoo males aggress their mates yet that answer still eludes me, though each passing year brings new revelations.

Male cockatoos, including those from long established pairs that have bred very successfully for many years, can suddenly cause great pain to their keeper, who finds the hen viciously injured or dead; the mandible will display trauma and in some cases the head, wings and body will display bite marks. I have found that trauma is most common to the upper mandible but that it is also seen in the lower mandible. The trauma may be as simple as some puncture wounds to as serious as the amputation of the mandible. I have also seen males that not only killed their mates but who then proceeded to remove a leg or wing, chewing on them like they would a twig when found by their caretaker.

Decades ago it was believed that the males attacked their mate because they were unreceptive to breeding. The male wanted to mate and she eschewed his advances. This was believed to have triggered an escalation in the attempt to mate and eventually an attack. The occasional hen was found dead while incubating eggs or even while rearing young. These latter incidences were considered anomalies; the focus was on an unreceptive hen.

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cacatua moluccensis

Young Moluccan Cockatoos bred by the author. (c) Tony Silva

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I was never fully convinced that mate aggression was solely due to rejection on the part of the female. During the years, I have spoken to various veterinarians, who have found no link to mate aggression with the breeding season or the degree of sexual stimulus in the hen; indeed in over 49% of the cases necropsied by three veterinarians, the hen displayed follicular development. Males were killing their mates as a response to factors that were not limited (though apparently include) breeding.

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Until some of years ago I was convinced that cockatoo male aggression was only seen in captivity. It was an artifact of captivity, of keeping two birds together in a cage from which the bird could not escape. I have now discarded this belief. Dead hens displaying the injuries typical of mate aggression have been found in their nest in the wild (Peter Chapman verbal communication, 2013). I also found evidence of this in Indonesia, when a climber who had scaled a tree containing a cockatoo nest to measure the cavity interior, found a partly decomposed body. The bird displayed the typical crushed mandible. Also in Indonesia I was shown a badly injured bird that was near death. It was a hen and her upper mandible had been crushed. Two other incidences are suggestive of cockatoo male aggression, though some predator could well have attacked the two incubating hens involved.

When I asked Don Wells, an aviculturist par excellence and a person who has had considerable field experience and whom I respect immensely, if he had ever seen evidence of cockatoo aggression, he responded in the affirmative. He had seen hens with healed punctured wounds across the bridge of the beak. Similar observations have been made by trappers in the Solomon Islands, New Guinea and on multiple islands in Indonesia.

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File:Cacatua alba -Bali Bird Park -crest-8.jpg

Another aggressive species – White Cockatoo. (c) www.viajar24h.com, This file is licensed under the Creative Commons Attribution 2.0 Generic license.

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Aggression is most common in the white cockatoos but it has also been reported in the black cockatoos and Galah or Rose-breasted Cockatoo. In the white species, the Moluccan, Ducorps´s, Red-vented, the corellas, Major Mitchells and Sulphur-crested cockatoos (both Cacatua sulphurea and Cacatua galerita) are the species in which more incidences are reported. In my opinion the long-term survival of the Red-vented and Ducorps´s Cockatoos in aviculture is doomed as a result of mate aggression.

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Based on the above, we know that mate aggression incontrovertibly occurs in the wild, that it is not necessarily linked to breeding and that it must be understood and controlled in order to safeguard captive populations of several species that are in serious decline in the wild.

Let´s start to dissect possible causes and solutions.

First I will enumerate the list of alleged causal factors: illness, either clinical or subclinical; confinement in too small an enclosure; imprinting on the caretaker; agitation by other birds of their kind or even the same genus; hormonal changes; a dietary imbalance; the offering of an inadequate nest—usually too shallow; incompatibility; and the aforementioned breeding asynchrony.

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The Philippine Cockatoo represents the most agressive cockatoo species. (c) Katala Foundation. This file is under the Attribution-NonCommercial-ShareAlike 2.0 Generic license.

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Having a cockatoo compatible pair is in my opinion the first line of defense. Pairing two birds that are incompatible greatly heightens the risk of injury. Allowing natural pairing and pairing birds of the same age is important and in my opinion reduces the risk. If an elderly male pairs with a younger female, a Suprelorin implant can lower his libido until the hen matures. Pairing two young birds if only two individuals are available would be the next best option. By growing together, one can expect compatibility to develop.

Aviculturists have responded to the threat of male aggression by clipping the flight feathers from one wing, this to slow the male. Wing clipping is partly successful if the flight cage is sufficiently long enough to allow a hen to fly out of reach. The minimum length would be 12 feet but much longer flight cages would be even more successful. A male intent on injuring the hen will persistently chase her until she is tired, when he moves in for the kill; I have seen such males stop eating and enter a murderous mental state that is not easily described. The longer the cage and more difficult it is for the male to reach the hen, the greater the chances the hen will remain unscathed.

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Even in a long flight cage, making it difficult for the male to approach the female will further reduce the risk of injury. Offering a nesting box with two entrances will prevent the hen from being imprisoned inside, where she can be an easy target. The double-entranced nest should have a divider down the center so that the male cannot simply enter, perch near the top and block the female´s exit. The female should be able to escape easily by exiting out through the side opposite to the male. The cage should also contain obstacles to make difficult an attack.

A male with clipped wings can grasp the side of the flight or perch suspended from the aviary roof to try to catch a flying female. Solid aviary sides and a roof can make this difficult. (The enclosure can have open ends and an enclosed mid section, as cockatoos come from relatively open forest and dislike dark enclosures.) The male would then be relegated to walking to the enclosure floor, across the aviary and climbing to a perch, this while the female can flee easily. Where the cage center cannot be made solid, baffles suspended from the enclosure roof can be used.

These should be suspended on multiple successions on opposite sides of the aviary. They should allow a gap sufficiently large to permit the female to maneuver in flight from one end to the other while making it difficult to the male to pursue her. Baffles are normally used for the smaller species, whose lesser weight may allow the males to glide some distance even with clipped wings.

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Title photo: (c) Valerie Everett. This file is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.

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