There is no other way of putting it: a huge blue cock will stand on the fourth plinth in Trafalgar Square in 2013.

The 14ft (4.3m) aqua-marine blue cockerel, Hahn/Cock, which will be made in Germany, is one of two contemporary art commissions announced at London's city hall by the mayor, Boris Johnson.

It will go up in 2013, with the 2012 spot being filled by an anti-war bronze statue of a boy on his rocking horse designed by the Scandinavian art duo Elmgreen & Dragset.

Johnson conceded that there was no getting round the fact that a giant blue cock was going up in the square where it will stand proud with the other plinth inhabitants – George IV and Victorian generals Henry Havelock and Charles Napier.

Johnson assumed Katharina Fritsch's cock was a French one. "The only consolation I can offer is that despite this gigantic French cockerel being in Trafalgar Square, we will still have Nelson looking down on it."

Fritsch, though, said it was non-specific bird. It could be English but it would be made in her native Germany. And the double meaning was not lost on her. "People try to avoid the word cock – they say cockerel," she said, laughing. "I'm playing with that a little bit, sure."

The work was more of a comment on male posturing, she said, as well as the cockerel being a symbol for regeneration, awakening and strength.

The first work to go up will be Elmgreen & Dragset's bronze boy in 2012, or to give it its formal title, Powerless Structures, Fig 101.

"I'm not going to try and guess what the significance of the boy on the rocking horse is," said Johnson, before having a stab. "Is it a homage to Rolf Harris? Is it a reference to DH Lawrence's famous short story?

"I think it may be a very subtle reference to the Olympic year and the fact that Team GB is very successful in Olympic sports that involve sitting down such as sailing and rowing."

According to the artists it is none of those, although he was probably closest with Harris and Two Little Boys. The work is, said Michael Elmgreen, more of a mocking reference to all the grand generals and war heroes who occupy the square.

"It is first of all a comment on the tradition of monuments that are very authoritarian, like the ones in Trafalgar Square. They look scary. Being heroic can have a different dimension to winning a war, it doesn't have to be about victory or defeat."

Since Mark Wallinger's Ecce Homo went up in 1999 the Fourth Plinth programme has become one of the best-known contemporary art commissions any where. It has included Marc Quinn's Alison Lapper Pregnant, Rachel Whiteread's Monument and Antony Gormley's One & Other which saw members of the public elevated up to the plinth for an hour at a time.

The winning commissions were chosen from a shortlist of six by a committee chaired by Ekow Eshun, the former executive director of the Institute of Contemporary Arts, and including the broadcaster Jon Snow and the artist Grayson Perry.