I have a very tall pine tree on my property in Pinelands, Cape Town. On many past mornings, it has been the roosting place for a pair of Egyptian geese. Now understand – it is not their nesting place – they arrive at daylight and start honking soon after. The honks go on for about 30 minutes, until everybody and the neighbours are wide awake and then, out of the south-west, a flock of Egyptian geese arrive and the pair, honking wildly, fly off to join them.

The characteristic honk is not a simple tweet or twitter. The goose gives off the honks on bursts with about 12 seconds between them. The bursts can comprise between five and thirty individual quacks, with a quack rate of about 160 quacks a minute, or just less than three quacks a second. I find this complication of the call of the goose to be surprising. Bantams and chickens have ‘signal-type’ calls, which are, basically, twitters that are fast repeating or slow, or a mixture, all of which indicates contentment, danger or availability of food. The calls are not group-specific – a bantam and a Rhode Island Red will give very similar calls.

I theorised that the geese in the tree acted as a sort of ‘nondirectional audio beacon’ for the flock – that the flock flew in a certain direction guided by the honks of the geese in the tree early morning. However, it would not be necessary to have a complex honk for this – a simple hoot would do.

So, my thoughts turned to the blind bombing system used by the Germans in World War II when bombing England. The beam from a radio transmitter would guide the bombers towards the target, but could not tell them when they were over it. To add to this ranging feature, a second, similar transmitter was set up in such a way that its beam crossed the guidance beam at the point where the bombs should be dropped. The aerials could be rotated to make the beams from two transmitters cross over the target. The bombers would fly into the beam of one and fly until they started hearing the tones from the other (on a second receiver). When the steady ‘on course’ sound was heard from the second beam, they dropped their bombs.

Applying this to the geese: we can assume that the honk from the tree is about 80 dBA. This sound will be audible by the incoming geese at about 1 500 m away. When the incoming geese hear the honk, they honk back. The return honk will arrive about four seconds at the geese in the tree, which will then honk back and then receive a further return honk, all of which will have an overall cycle of 12 seconds.

A goose flies at about 10 m/s, so, in the honk ‘cycle time’, the goose will travel 120 m, which is why the honk cycle is not continuous. I guess that, in fact, the goose that acts as the beacon more or less hears a continuous honk, from either the goose or the incoming flock. All of this I worked out while drinking my coffee in the early morning.

Something happened recently to support my theory – I acquired some chickens. My friend who gave them to me generously included some cockerels. Would their crowing disturb the neighbours? As soon as the chickens were housed, the following morning, at 04:00, their first crows were heard. Then again at 06:00. And at 08:00.

The Egyptian geese no longer come to the tall pine tree. Does the cock crow disrupt their honk system? I can only conclude that it must; nothing in the past – shouting, shaking the tree branches with solid paint balls – has made any difference. Thus, I may have stumbled on a good working solution to disturbance by Egyptian geese. Remember, you read it here first. Chickens are the answer.