Feeding white bread to your local birdlife could cause 'angel wing' like that suffered by this goose.

A classic Kiwi pastime is causing more harm than many realise and councils are taking steps to put a stop to it.

The Waimakariri District Council posted signs at the Kaiapoi Lakes last week, warning against feeding bread to ducks and other local birdlife.

The call for the signs came from the South Island Wildlife Hospital earlier this year, and after several months a sign was posted at the Kaiapoi Lakes.

ANDY JACKSON/FAIRFAX NZ Feeding ducks bread could be damaging their health.

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Hospital spokeswoman Angela Tranter said one of the negative effects of feeding bread to birds could cause a debilitating condition known as angel wing.

She said this left affected birds' wings pointing out laterally, "rather than resting against the body, rendering them in many cases unable to fly – which could obviously be fatal.

"It's an incurable condition brought about as a result of a high-calorie diet, one extremely high in protein and carbohydrates and low in vitamins D, E and manganese – the exact diet a bird would get if they primarily ate white bread."

Christchurch City Council garden and heritage parks operations manager Jeremy Hawker said "friendly signage" would be going up at the Botanic Gardens from spring to remind people not to feed bread to birdlife.

He said a new cafe at the Tea Kiosk had been offering alternative bird feed options since opening last year.

"We recognise visitors appreciate the opportunity to feed the wildlife, particularly ducks, and we wish to educate them on alternate products.

"Feeding ducks with bread is a well-practised habit, and change may be gradual."

Tranter said the harm of the "age-old" pastime was unknown until recent years, and because it had always been done, there had been some resistance.

"I did see on an Oamaru Facebook page last year a wee bit of a negative response to their council's signs going up and saying how disappointing for the kids etc.

"So even with the knowledge it's not good for our ducks, some people still feel it's their 'right' to do it."

A spokeswoman for the Ashburton District Council said the council currently had no policy about feeding the ducks, "as they are wild animals".

"We don't have control over if or what the public feeds them. It is not something we plan on looking into in the future at this point. We do have protocols about how the birds in our aviaries are managed, but again, this does not apply to wild birds."

WHAT TO FEED DUCKS:

* Wheat, barley or similar grains

* Oats (uncooked; rolled or quick)

* Rice (cooked or uncooked)

* Birdseed (any type or mix)

* Grapes (cut in half or quartered if very large)

* Nut hearts or pieces (any type but without salt or flavouring)

* Frozen peas or corn (defrosted, no need to cook)

* Earthworms

* Mealworms (fresh or dried)

* Chopped lettuce or other salad mixes

* Vegetable trimmings or peels (chopped)