Once an Asian hornet starts visiting the bait station regularly, watch carefully as it leaves to see the direction in which it flies away. Ideally, use a compass, otherwise note carefully the landmark that best shows where you watched it disappear. You will be able to measure a more reliable direction against a distant landmark than against a nearer one.
The direction of flight will be visible over a greater distance if your vantage point is slightly elevated. A bait station set amongst trees or very close to a hedge or building may give only a very limited distance of visible flight, so it will be impossible to tell which way the Asian honet has gone after it disappears around a tree or over a hedge.
Ideally you should have a very largescale map of the area to identify individual properties, fields and clumps of trees. These can be printed from Google Earth (preferably A3 sizee). On the map, mark the precise position of the bait station and carefully draw a line to show the direction of flight. Ideally, measure it with a compass (beware of causes of compass deviation such as a mobile phone or the bonnet of your car under your map!). Otherwise note distant landmarks carefully as the Asian hornet disappears out of sight and use those to mark the direction on the map. It is important to observe several flights to confirm the direction of flight before using that to decide on the next step.
Remember as you mark the direction on the map that you have succeeded in tracking Asian hornets only as far as you actually watched them fly. They may have deviated at a nearby landmark as soon as you lost sight of them.
Asian hornets can fly approximaely 3 metres per second - 5 seconds of sight will give you only 15 metres of reliable direction. Therefore, further bait stations will need to be placed ahead in a series of steps to confirm the nest location.
Once the Asian hornet has established a regular visiting routine, start timing accurately how long it spends away from the bait station before returning. As a rough guide, you can expect a nest to be 100 metres away for every minute of absence before it returns to the bait station.
Also be aware that Asian hornets don't necessarily fly straight back to the nest or fly directly back to the bait station. It may take a while for them to develop a regular pattern of visits, especially if they didn’t finish feeding on the bait station before being caught.
Asian hornets tend to follow the contour around a hill rather than fly up and over it. They also tend to navigate their way by visible landmarks, such as hedges, roads and buildings so may be taking a rather round about route.
Another factor to take account of when timing is that if the bait station is close to or below,the nest, they may fly away in another direction at first while gaining height.
With repeated visits to the bait station, Asian hornets tend to develop a more direct route once they have learnt the way. Their return times will then reduce and give a more accurate estimate of the distance of the nest.
Return times of less than 2 minutes indicate that you are getting very close to the nest. You may never get times of less than a minute because when you are very close to a nest in a tall tree, they will still spend time gaining height to reach their test.
Once you have consistent return times and direction, move your bait station closer to the nest in the direction of flight.
Depending on the Asian hornet action team available and the terrain, put out another two (or more) bait stations beyond the estimated distance of the nest to get them flying back in another direction.
Having three bait stations in a triangle enables you to use triangulation, by plotting three recorded flight directions on the map and seeing the three lines crossing at a point. This should indicate the location of the Asian hornet nest. Ideally, the three bait stations should be in an equilateral triangle, but placing them with clear lines of sight along the flight paths is the most important consideration.
Before any bait stations can be placed, always seek the landowner's permission to access their land. If you cannot find anyone, the placing of bait stations should be somewhere nearby on land where access is permitted.
Most Asian hornet nests will be found high up in tall trees, but some have been found at lower levels in brambles and hedges. Do not disturb a nest as Asian hornets can be highly defensive and be extremely dangerous.
Nests located high up in trees are notoriously difficult to spot from directly under the tree. It may be better to stand further back and look up to spot any signs of many Asian hornets flying to and from an area in the tree canopy, to then follow one of them to a particular tree, and only then to spend time looking up at the tree top for the silhouette of a spherical nest.
Once the nest has been found, only qualified pest controllers can then destroy the nest.