How to protect your pondfish from Herons
The Grey Heron (Ardea cinerea) is one of the UK’s largest birds, standing short of a metre tall, and with a wingspan a little less than two metres. With their impressive beaks they seem almost Pterodactyl-like when seen in flight, and their distinctive long and deep squawk just adds to that. You might miss seeing them as they often visit ponds at first or last light. The only hint may be a discarded fine feather floating on the water… or the lack of fish! You are unlikely to lose all of your fish in one visit, though it may seem like that, as the remaining fish often keep a very low profile for some weeks or months afterwards.
There are plenty of herons in the UK, possibly helped by the fact that they are a protected species. They usually roost in rural treetops but can travel long distances and are common visitors to city-centre ponds. An adult heron needs up to half a kilogram of food a day, and they will persist to obtain it, be that fish, frogs, voles, insects or even young birds.
Ornamental ponds with brightly coloured carp and goldfish can be easy pickings for herons, especially in the cool of the spring and in the winter when the fish are sluggish and plant cover is lacking.
Best Options to dissuade Herons
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Netting over the pool comes top, though determined herons may still try to pick at fish through the net.
Fine Nets (15-30mm gauge)
A fine cover net is the ultimate deterrent, but unsightly and more likely to become tangled with marginal plants. It will be of some use even if only used in the winter months, when the plants have been cut back, and can be useful to keep out autumn leaves as well. Moulded or knotted square mesh tends to be easier to keep taut over the pond than the knitted diamond meshes.
Coarse Nets (50-100mm gauge)
A number of my customers have had success with a 4 inch square black mesh, held taut 30cm or more above the water. It is light and relatively invisible, allowing plants to grow through, whilst still giving access to the water’s edge for small birds. It will need removed for pond maintenance. (We can get this mesh custom made to suit your pond size).
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Suspended Lines can be stretched around the pool edge at 15 and 30cm heights, held in place with canes, or specially made supports in wire, metal or plastic. Nylon fishing line is least obtrusive, electric wire versions are also available. This disturbs the heron if it tries to access the pond from the sides, though it is of less use in larger ponds with ample shallows where birds can land straight into the water.
Deep Areas provide a good refuge for fish. Herons much prefer fishing in the shallows, so ponds with steep sides and ample depths (1.2m/4ft or more), such as those found in ponds specifically for koi, are a bit less vulnerable. Unfortunately, the heron can still swoop and stab at fish near the surface, so pondfish are only safe once frightened into the depths.
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Enclosed Situations: Ponds overhung by trees; really close to houses; in courtyards; and near reflective windows, all seem to be less vulnerable to heron attacks, though there are no guarantees, and hungry herons might still try. © www.watergardensolutions.co.uk
Pond Grids: Custom fitted pond cover grids or floating grids can dissuade herons, though they may still try to pick around them to get at fish. Unfortunately such grids make the pond difficult to maintain, and they can be unsightly if scale and algae starts to gather around them.
Deterrents and Scaring Devices: Various devices are on offer, from elaborate electronic sensors that flash and screech or even spray out jets of water, to simpler floating reflectors. Most deterrents tend to work for a while, until birds get used to them and work out how to avoid them. Moving the devices about regularly can help a bit. The downside is that sensors can be set off unintentionally by you or your pets, and deterrents may keep away other small birds that you’d rather attract. Water-jet types can also freeze up in the winter.
Hides: Creating areas where fish can take shelter is worthwhile and easy if incorporated at the design stage. Gaps under plant or ornament supports, or in cavities under stepping stones, or between planting containers, can all be of help. A large bore (15cm/6” or more) section of pipe on the pool base is another option, but can be unsightly.
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Disturbing: Children, dogs, and irate pond-keepers can all help to scare herons off, but these birds are surprisingly persistent creatures and they will return when you’re not about, even if you’re only just out of sight.
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Ornamental herons in brass, stone, plastic, whatever… don’t work! Herons can be solitary, but they feed in groups too.
This information sheet was adapted from one of our newsblog articles which also carries comments and some links to other sources of information on herons.