A chicken?

A lone chicken? "Yes," says Alan Richardson, director of arts organisation Conflux, with one of those wry looks that suggests I'm getting little more information out of him on this issue. "A chicken lady." But chickens can't really fly? "It's one of the little stories that happens in amongst it."

You'll be confused, I'm sure. I don't blame you. I was when the matter of the chicken came up. What this chicken - the one Richardson speaks of - is doing in Perch, the major outdoor performance about flying and falling that takes place in Glasgow next weekend, is anyone's guess. Richardson knows, clearly, but he's not giving any details away.

Mostly because he can't. "Loads of stuff is yet to be made," he tells me when we meet at the Briggait, where Conflux is based and rehearsals for the show are taking place. "There is improvisation in terms of rehearsal [still to be done] which will be turned into fixed choreography for the show."

What Richardson can say is this: Perch is one of the most ambitious street performance projects Conflux, which develops street arts, physical theatre and circus across Scotland, has ever been involved in. Taking place around and on top of the buildings in Rottenrow Gardens in the city centre (the site of the city's old maternity hospital) it will involve around 50 performers (including Scotland's leading street artists, circus performers and aerialists), the 86 piece National Youth Orchestras of Scotland's Senior Orchestra, plus projected film and animation.

Perch will also be performed simultaneously in Largo do Rosario Square in Campinas, Brazil, with live video streaming linking the two performances in real time. Richardson describes it as a "carousel: a 360-degree experience", with the performance surrounding the audience on the ground and above them on rooftops.

The show, which is being billed as a highlight of the opening weekend of Festival 2014, part of the Glasgow 2014 Commonwealth Games Cultural Programme, and SURGE Festival, is a cross-continental collaboration involving Conflux, award-winning Australian physical theatre company Legs On The Wall and Brazil's world-respected centre for performance LUME Teatro. Not to mention the musical score which has been specially created for Perch by Scottish-based Irish composer Stephen Deazley.

Patrick Nolan artistic director of Legs On The Wall and Ricardo Puccetti of LUME Teatro are co-directing the performance, which will invite the audience into a bird-like world with five different groups: the furious, the travellers, the fashionistas, the medics and the zookeepers. "Theatrically it's about people being quite stuck in their ways and then what happens if you try and move them away from that - what happens if you try and move away from your own group," explains Richardson. "All the movement is based on birds but they are quite humanesque, the furious are the least human."

Itxaso Moreno, a Glasgow-based actor originally from the Basque country, plays the leader of the furious group. She describes her character, Sylvia, as "like a glue that glues all this world [together]". Moreno adds: "In terms of what my character does it's like this world was a playground for me and I'm making things happen but also taking a step back and letting them be and exist. Although I'm kind of leading one of the groups I have a relationship to all of them as well. It feels a little bit like a mother who is letting go."

Moreno describes Perch as "an immersive experience. It's like we're inviting people to enter this world which is heightened. Within that world different relationships are happening, different things are happening but it's not a big elaborate story where there's a moral. It's about flying and falling and from my character's point of view it's more about the experience."

This role, says Moreno, has been particularly challenging from a logistical point of view. Some of the performers will be taking part in aerial work on top of the Rottenrow buildings, while others will be on the ground and among the audience. She adds: "The challenge of a project like this, a very obvious one, is the logistics of bringing everyone together, getting everyone to work together and have a cohesion, but at the same time be quite individual and also we're working outdoors."

Certainly putting on a production of this scale, involving aerial work, old buildings and a live audience on the ground, has required a lot of technical preparation. Specialist equipment, structural engineers, rigging experts, safety considerations and all before the performance could even be fully planned. "There's been a lot of engineering and mathematics involved," adds Richardson.

The Brazilian performance will take place on a similar scale, around the buildings of Largo do Rosario Square, with around 80 performers and a 93 piece orchestra which will also be playing Deazley's score. The live video feeds will show each city what is happening in the other and also include rhythmical speaking from Brazil that the orchestra in Glasgow will play along to live. Logistical nightmare doesn't even begin to cover it. "I'm a bit greyer and slightly balder than I was at the beginning of the year, but it's all really interesting," says Richardson.

A world of bird-like creatures spread across two continents, accompanied by music, animation and featuring vertigo-inducing stunts on top of old buildings, the message is clear: Perch isn't your average street performance. "I don't want people thinking they're coming to see Macbeth because they're not," confirms Richardson. "It's an outdoor experience involving theatre and music and film and circus and all sorts." All sorts, and a chicken.

Perch: A Carnival of Flying and Falling will be performed as part of SURGE and Festival 2014 on July 19 & 20 at Rottenrow Gardens, Glasgow. Visit www.perchcarnival.com