ahah, someone mentioned herons, this can summon 'the heron file' compiled from various ponders experience, over the years....
Herons have a muddle of habits, some go in for neat extermination jobs, others may be picky, leaving the whole body of a fish and only eating the tail section. Go round a lake after herons have been and you will find a lot of variation in kill habits... Yes, they will fly around and around a location on many days before even landing on a tall tree close, for a more careful look... Very keen eyesight and hearing
After a serious heron attack, its normal for fish to go hiding for weeks, so you never know what has happened.... on a well planted pond with a lot of cover, most fish survive though you will notice the dramatic difference in their usual behaviour and wonder why.
Here's a few notes collected from observations and other folks experience
1) Predator nets.... cheaper than losing koi, downside, local animals can get trapped in it, snared. Not very pleasant explaining to your neighbor why their pedigree cat or dog lost its life or leg through strangulation. Predator nets are probably the most cost effective barrier method, a large mesh of around 4" should allow most varieties of plants to grow through it without tangling the mesh. Smaller meshes tend to be a mess with plants, strangled pets, and dead frogs by the time Spring arrives...
2) Barrier method.... Suspend strong fish line taut, at a height of 12" over and around the pond, herons hate trip wires. An elegantly simple way to baffle a dim fishbag on stilts, it often works, many folk have reported seeing herons 'baffled' this way.... a near invisible line that they can't see, bump into, cannot step over without tripping, is enough to stop them.... I guess herons have yet to master the skill to sneak along the ground without the use of their long leggedy stilts...
3) Hiding places... Step up cover within the pond... water lilies.... big bits of pipe, float large sheets of black polythene (trash bags will do) trippy stuff for tangling up predators... hiding places for fish. Surprisingly, many black plastic objects, when submersed become virtually invisible, in a natural setting, so the idea of this clutter in pond is not as bad as it sounds.
I like this method, it creates a lot of hiding places and is virtually invisible to the usually attractive pond setting, it makes it very difficult for the likes of persistent herons and raccoons when they raid.... useful in winter when foliage is bare and fish want somewhere quiet, to hibernate. Bare crystal clear ponds must be an easy target for predators, the garish and brightly coloured fish must just shout loud and clear, 'sushi bar' to every itinerant fish eating scoundrel passing within sight overhead.
4) Pond design... When you make a pond, make 45° sides, herons have gangly legs, they like 'easy walking' conditions, they hate 'trippy' pond surroundings... The one common weakness of predatory birds is the vulnerability of their gangly long legs, they absolutely rely on an easy landing place, and an easy stroll into the pond, handy shallow terraces are a big help....
5) Trapping... I can't be so fiendish, I cant advise you put out snares... a simple loop of fish line can lock onto a predators leg. Nasty way to die, that
6) Shooting... Not everyone in the world live in areas where herons are protected, or rare... I can't recommend a .22 air rifle, a bit politically incorrect, even though a heron is easy to hit at 200' with a decent scope, unfair, too easy I guess. Anyone who has used a rifle properly could hit a quarter at 100 feet so for the squeamish, clipping some tail feathers is possible .....or hit a bucket placed beside the pond loud and close enough to frighten the bejasus out of the vile fish bag... that is an effective clean way....Alas rifles in most peoples hands are counter productive, you can waste a lot of time waiting for the opportunity to use it, to learn how to be competent with a rifle and the consequences of a bad tempered person with a lethal tool is well, unpopular...
7) Sprinklers... For the flash and the opulent, linking a motion detector and a sprinkler might provide some amusement to scare off the dratted bird. Or, a hose with a timer, that briefly blasts water every 15 minutes or so, enough to startle a pest... if the risk of absent mind folk getting a drenching is bothersome, perhaps the motion detector could be linked with an emergency service strobe light, that would be enough to freak most long leggedy villains away
8) Aquatic plants... A heavily planted pond makes life very difficult for predators, even though the dumber fish will always be taken first, shy timid (smart) fish and the little 'uns ought to find good hidey holes easy... rafts of aquatic iris, water lilies make life difficult for hunters to find fish, let alone move around, risk stumbling
9) Fish feeding routine.... Have a special food signal, like tap a stone three times at feed time. You don't want your fish to associate every visitor to your pond, with a free meal.... one day it will be a heron, looking for freebies...
10) Heron statue... what a novel idea, picturesque even. They always seem to be coming on the market, second hand. Never heard anyone had any success with them, other than folk who sell them. Now I have heard of someone linking an owl statue to a motion detector, they swore that worked... that would be a hoot if it tooted when motion was detected.... A convincing statue of a cat, or a dog moved about the pond area, that might have some effect
11) Sonic guns.... A promising new device coming onto the market.... sonic 'guns' that fire a narrow band of extreme noise in a confined direction. Link this to a motion detector and it really will do the job... herons are sensitive and nervous, a violent sound like that pointed at the pond area will blow them away when they trigger the sonic gun. Because of the controlled direction of the sonics, not likely to bother neighbours, much.... Very promising... Another device that can be activated by a motion detector is a strobe light, the sort that emergency vehicles use, that can drive off predatory birds which are unable to hunt with such a distraction... has been reported to keep fish ponds free of attacks recently, not a big deal to find and install.
12) Baseball bats. Herons by nature are incredibly careful hunters, you won't get within 50 feet with a bat. Anyone thinking of trying such a method will quickly learn the bird is a lot smarter than them, that will be just sooooo embarrassing....
13) Fake crocodile heads... might well work in Southern areas where crocodiles are well known predators. Spectacular episodes of lurking gators, flashing of teeth, boiling water as the gators charge upon unwary herons would stick in the mind of the cunning and sneaky heron. However, many herons are not familiar with crocodiles at a young stage, or have never seen them before so in many cases it just won't be noticed, except, in areas where crocodiles are well known...
14) Tin traps.... A 'scarer' for discouraging prowlers could be a tin trap, a big can with some large round stones to rattle loud within, precariously perched, attached to a fishing line trip wire along likely approaches. Very effective after dark and around morning and dusk...
15) Shishi odoshi.... Another critter scaring method, which may or may not work against predatory birds but is supposedly effective against deer is the Japanese 'shishi odoshi'....If it is a little out of the way without too close neighbours, this old japanese design for scaring deer might be effective, made out of a few large pieces of bamboo and relying on a trickle of water to keep it going, it's supposed to work on deer. Moose might be a different matter... It could drive you nuts if you made it a little loud...
Checkout:
http://www.canadianhomeworkshop.com/weekend/shishi_odoshi.shtml
16) Koi 'decoys'.... Folk are reporting they work. Someone somewhere makes rubber? koi which you can moor in the pond in an open area... looking like a dozey sitting 'duck' the heron sneaks up, batters at it a few times, tries to yank the koi plus anchor out of the water, only to discover it can't.... by which time all the real koi are well alerted and in hiding, having a good snicker, I hope. Definitely one confirmed report from a chap who watched a heron outwitted by a decoy battering at the rubber koi on his koi pond, wrestling with the anchored faux fish, that can be said to contribute to improved safety for pond fish, provide rubber sushi
17) Trusty moggy.... Since adopting a wonderful little grey cat, that has an astonishing capacity for commanding its territory and all that it surveys, especially through the twilight hours I've never seen any heron land.
Yup, an over zealous, pouncy whirling dervish of a killer moggy that spends its time dreaming of such gigantic drumsticks would be an effective deterrent to an experienced heron.
The memory of a whirling mass of tooth and claws bounding three foot into the air towards their neck would remind them to not go close to a well stocked sushi bar where a well clawed and fanged guardian roams
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The time when predatory birds go pond hopping is often determined by local factors, drought, floods or freezes have made difficult or clouded their usual hunting places, early morning and fog is often a factor to make them bold enough to go close to places where ponds are, compact sushi bars are preferred....
Herons are creatures of habit, they will 'tour' their favourite water holes. When they spot a new pond with fish they will add that pond to their schedule and turn up like clockwork with the same routine...
Their eyesight is extremely good, it is something of a big advantage if the fish turn out to be garishly bright koi or goldfish... Not unlike a neon sign shouting 'sushi bar' loud and clear...
The loathsome fishbag on stilts might circle a promising pond a couple of times about 400 yards away, checking the whole area then appear to disappear over the horizon... They will disappear if they have spotted anything lurking, perhaps a cat, or fox is about...
Several minutes later, they will overfly it once or twice, gliding slow, to bank and turn and seem to go away. Five minutes or so they then come very slow, steady and at a low height from a completely different angle as if to take by surprise any skulking entity... hedgehopping, literally...
Should they spot one little thing that frets them, they will abort landing...
They want the pond all to themselves, with no complications like dogs, or people about...
Only then, when they are absolutely sure it's safe to plunder, will they come in and land in a high place overlooking the pond. Perhaps a chimney, or a small tree close to the pond.
Herons often explore ponds in gardens during times of poor visibility, fog, at first light when their usual haunts have become difficult, for example when floods have clouded waters, or when ice has formed, the conditions for likely heron attacks can be predicted if you keep an eye on the weather forecast...
When they have landed at a high vantage point overlooking the pond area, they really take their time and look with those beady little dark eyes, to make absolutely sure nothing is lurking before flapping to the best landing spot close to the pond...
I say they, because it is not unusual for them to go about in pairs...
Should your pond be netted they will go to some lengths to try and get within, finding or forcing any gap that they can... When they are safely well within the net, that is a good time to, errr....
...surprise them
Medieval historical re enactment folk may fantasize at will as to what clubs, trubuchet, mace, crossbows might have been on hand in the good old days for moments just such as this
regards, andy
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