The birds kill sticklebacks by striking them against their perches, which softens the spines of the fish, making them easier to swallow.
But a kingfisher at Montrose Basin appears to have gone a step further by using the spines to pin three sticklebacks to its branch.
The bird's unusual behaviour was captured by photographer Ron Mitchell.
Anna Cheshier, Angus ranger at Scottish Wildlife Trust's Montrose Basin wildlife reserve, said the kingfisher visited every day.
She said: "The photographer who took the images didn't realise what he had captured until he took them into the visitor centre the following day.
"It's hard to tell if the kingfisher has hung the fish on the branch accidentally or on purpose, but this is really unusual behaviour that no-one seems to be able to explain.
"We'd like anyone who has seen anything like this before to get in touch."
Kingfishers are found around lochs, ponds and rivers and rely on clean water to be able to dive for small fish and aquatic insects.
There are around 5,000 breeding pairs in the UK.

It says homeowners borrowed Â£220.3bn last year, up 8% on 2014 and the highest since 2008's total of Â£247.8bn.
However, the figure is still well below the Â£356bn lent at the peak of the property market in 2007.
The CML said lending had recovered faster than expected. Growing wages, falling unemployment and cheap mortgage deals were among the reasons.
Nevertheless, it said the outlook for 2016 was less certain.
"The supply of existing and new properties on the market remains weak, and affordability pressures weigh on activity," said CML economist Mohammad Jamei.
"There is an added element of uncertainty as we wait to see the impact of tax changes on the buy-to-let sector."
Buy-to-let landlords face an increase in stamp duty from April, and a reduction in tax relief from 2017.
Photographs showing a kingfisher appearing to hang fish out to dry has baffled experts at a wildlife reserve.
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Mortgage lending in 2015 was the highest for seven years, according to the Council of Mortgage Lenders (CML).