We all know the distinctive call of the magpie – those black and white highwaymen who perch in macrocarpa trees waiting to dive-bomb passing cyclists. Since arriving from Australia in the late 1800s, magpies have become a fixture of the New Zealand landscape, and as their numbers have increased, many people have witnessed a corresponding decline in native birds.
Magpies are fiercely territorial when nesting and often drive away other birds. Mostly it is by subtle harassment, but someimes they will attack and kill. Many people have witnessed magpies dive- bombing and killing kereru. On the other hand, magpies in large flocks do not have nesting territories, so they are not interested in attacking other birds – apart from hawks. But these large flocks provide the replacement stock which will quickly re-populate any newly vacated nesting territory, so in practice they need to be controlled as well.
I exhibit each year at the Mystery Creek national field days, and have had numerous conversations with landholders who have witnessed the effect of magpie invasions. The consensus is that magpies drive away native birds, and landowners have seen native birds return once they trap magpies.
Magpies mostly feed on pasture insects, preferring paddocks which are grazed short. They like to nest and roost in exposed trees or shelter belts which command clear views. Nesting magpies will often feed some distance away from their home territory.
There are four methods of control. My preference is to trap with food bait, but we will consider each method in order.
Trapping with a call-bird
The traditional trap is a Larsen trap, used with a call-bird. A central compartment houses the call-bird, with two or more side compartments to catch magpies as they attack the captive bird. When the magpie stands on the split-perch, the perch collapses and the door swings shut. Split-perches can be tricky to set. If they are too low they jam the door when closing, but if too high the magpie can walk underneath.
The best call-bird is a stroppy magpie caught at least a few kilometres away, which will sing and call inside the trap. The local territorial nesting birds will take exception to this foreigner and try to drive it away, but get captured in the process. If you are trapping a flock of non-territorial magpies, they will only be mildly interested in the foreign bird. They may come for a look, but will not be as likely to enter the trap.
The big problem with call-birds is the time and effort required to feed and maintain them. They have to be fed every day, and kept sheltered from rain. If they get wet they soon die from hypothermia. Some magpies do well in captivity, but many get stressed and die.
A variation on the call-bird technique is to mount mirrors inside the trap, so magpies looking in see their reflection and enter the trap to investigate.
Trapping with food bait
By far the easiest way to catch magpies is to use food as a lure. They eat all sorts of food, anything fatty such as butter, dripping, mince-meat, dog-roll, crumbled cheese, bacon or mutton fat. But they can be fussy and you may need to try a variety of foods to find what your local birds prefer.
You can use just about anything to catch magpies once they are feeding on bait. An old possum cage trap set with mutton fat on the hook can work. Larsen traps with side opening doors can be set with bait instead of a call-bird. Funnel traps can also be used. These are similar to an eel trap, with a large cage fitted with a funnel entrance leading to the centre. The letterbox trap is a variation on this idea. Designs for both can be found at http://icwdm.org/handbook/birds/Magpies.asp
Another option is the magpie trip-trap, which I designed and have manufactured for more than 10 years. It is lighter and more compact than the traditional Larsen trap, and is easier to use. Please contact me for more information.
Poisoning with alphachloralose paste
Alphachloralose is a narcotic poison available from farm supply stores. It knocks birds unconscious, and in cold weather they die from hypothermia. The theory is that non-target birds can be retrieved and placed in a warm place to revive. To knock out an entire flock of magpies you must pre-feed with non-toxic bait for at least a few days, so all the magpies will consume a toxic dose on poison day. Any magpies who do escape will be poison shy and will not fall for the same trick again.
Pre-feed at the same time early in the morning every day, preferably by the same person. Choose cool weather, and on poison day have a team of helpers ready with bags to collect the magpies as they keel over. If you have prepared properly they will all succumb at the same time and you will gather them up with no escapees.
The old joke about magpies recognising the calibre rifle you are carrying and sitting just out of range is no joke. They quickly get gun shy. To avoid that, you need a silencer and terrain that lets you sneak up without being seen.
Some people use a magpie distress call tape, coupled with a dummy magpie, to get magpies into range. However it is patchy and often the magpies sit in distant trees watching. One chap I met recounted shooting his cassette deck, which he did not notice lined up behind the magpie.
Disposing of magpies
Make sure the other magpies do not see you disposing of their captured mates. Either clear the trap in the evening when they have gone home to roost, or if during the day cover the trap with an old sheet to conceal the operation. Young magpies are least likely to become trap shy. It is the older birds who are most likely to associate something bad with the trap if you are not careful.
You can wring the magpie's neck for a quick kill, but they have a surprisingly strong neck for their size. You can hit them on the head. An air rifle works well, but resist the temptation to use a shotgun. Believe it or not, people have done it but it destroys the trap. The same advice goes for .22 rifles as there is a risk of bullets ricocheting off metal trap frames.