Tool use in parrots Anodorhynchus hyacinthinus

by Karl Fr. HOHENSTEIN. Published in Gefiederte Welt, Issue 12/87.

Anyone, who has had to accustom Hyacinthine Macaws just once to new foods, will know how nerve-wracking it is to wean them off palm nut kernels onto the parrot food available here.

In Brazil or Paraguay, where the macaws known to me have come from in recent years, they are fed exclusively on the kernels of the Acrocomia totaipalm nut.

These nuts can be bought in the market in Asuncion, the capital of Paraguay. The kernels are smashed out of their shells and used for baking, eating fresh or making soap. These nuts are much enjoyed by the Hyacinthine macaws. In fact I would say that that they can be bribed with these nuts to comply with all sorts of things. They will take them out of your hand without biting the hand because they learn after a while that a nut is hidden in the hand, which they will carefully seek out.

You can, however, run into difficulties when you try to wean them off these nuts by offering the parrot food available here. This will be ignored, including peanuts in the shell, hazelnuts, almonds, corn on the cob and similar food, even brazil nuts or pieces of coconut.

When the store of palm nuts is consumed, you come close to desperation as these are to be bought here. But in the end it is possible to accustom the macaws to the usual parrot food.

One disadvantage of the palm nuts is that they go slightly mouldy when stored normally. I was able to prevent this after talking to my local pharmacy by placing the nuts for half a day in a 4% solution ( 4g to 1 litre of water) of Nipagin (Acidum benzoicum) and then drying them off. The nuts then remain untainted for much longer. I have been able to store them for months in a dry cellar.

The last time I was in South America I collected palm nuts from Acrocomia totai to please my macaws. In addition I brought back a cluster of fresh palm fruits. They have the disadvantage of being very heavy. Moreover the outer layer dries out easily. Apart from that they are much enjoyed by the macaws. They can busy themselves for a long time, peeling off the outer shell and discarding it. I had at first thought they could obtain vitamins and similar substances from the outer shell, but this has not been the case as they dry out so quickly. These fresh palm fruits were also treated with Nipagin.

As mentioned above I also collected nuts, which had been lying on the ground for some time, some of which had been eaten by cattle, passed through their stomachs and excreted. You have to take care that you do not gather nuts where a beetle has laid an egg in the flower or the fruit when it was still fleshy, in which a maggot develops, which bores through the hard shell after having eaten the contents.

The macaws enjoy these nuts as well. They spend much time, which is certainly psychologically good, cracking the shell and testing their bill on the hard shell.

The palm nuts with hard shells measure on average 18 to 20.5 cm and weigh 4 grams. The kernel itself measures 12.5 to 14.5 mm in diameter and weighs 1.2 grams. The hard shell has a thickness of 3.2 to 3.8 mm. Fresh fruit with pulp measures 31 to 33 mm and weighs 15 grams. When dried out it weighs 6 grams. The palm fruit cluster is 35 to 50 cm long with a diameter of approximately 25 cm.

The macaws work on the palm nuts for 5 to 15 minutes, depending on their expertise in cracking them open, until they have made a round hole, which they then gradually enlarge. I have tried to crack one with a normal 10 cm bench vice without success. The macaws lay the nut between the upper and lower mandible. I should like to use this opportunity to report that I have observed various macaws shaving off a flat piece of wood , 3 to 4 mm long , from the perch to assist in gripping the nut. All the birds positioned the piece of wood above the nut between it and the upper mandible. When I saw this for the first time I was puzzled and thought that the macaw had picked up the piece of wood by chance. However I observed it many times and discovered that the piece of wood was only used for cracking these hard nuts.

In the meantime these pieces of wood, which were originally of green wood, have got smaller. The macaws are now happy to work with such small pieces of wood that they are only visible when taken from the perch, but not in the bill from the side.

On the other hand the macaws immediately altered their behaviour as soon as they were given a fresh piece of willow. From this they even removed small branches to hold the nut against the upper mandible.

I have shown this use of a tool by the macaws frequently to visitors. Such a use is seldom observed in animals and can be regarded as a sign of premeditation.

Enquiry

The publisher of Gefiederte Welt asked the author if the macaws were perhaps imitating behaviour, but his reply, which is given below excluded this.

The action of the Hyacinthine macaws, which are kept in an inside area was spontaneous. It was observed the moment they were given the palm nuts brought from Paraguay. They did not test or try it out. It's interesting that a Green-winged Macaw (Ara chloroptera did not attempt this. He is also not able to crack open the nuts, but plays however for hours with them. With the Hyacinthine Macaws it can only be traditional behaviour of wild macaws, which they learnt earlier.

Comment by website editor:

The observations of Karl Hohenstein are very interesting. I too have given my Hyacinthine Macaws palm nuts collected in the Pantanal, but these are from the acuri palm (Scheelea phalerata), which are elongated rather than round. The oldest adult male, who was wild caught many years ago taught the others - macaws bred in aviculture - to open the nuts with great precision. I have not noticed any of them using pieces of wood in the way mentioned above, but have often observed them using strands of cotton ropes hanging near the perch to grip the nuts. They all enjoy the palm nuts and will even ignore their favourite foods if palm nuts are available.

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