The four-foot sculptures, which have been exclusively designed for the Wildfowl and Wetlands Trust (WWT) will be displayed alongside some of their living counterparts at the reserve near Burscough.
They include a large North American River Otter, a Hawaiian Goose (Ne Ne), a giant Kingfisher and a flamingo.
Nick Brooks, Martin Mere’s general manager, said: “The characters look fantastic, especially Fred the Frog which took a whopping 244 hours to make.
“Exploring our amazing wetlands at Martin Mere to find the sculptures is great fun for all the family and a brilliant way to inspire kids to love wildlife and want to protect it for the future.”
As well as the trail, visitors will be able to take part in popular hour-long, interactive LEGO brick workshops.
Activities include working in teams to build as many ducklings as you can, an individual challenge to make a vehicle for a wildlife ranger mini figure, and the chance to build your own miniature LEGO figure to take home.
The giant LEGO brick animal trail is included with the cost of admission.
The workshops take place at weekends and half term and cost £10.50 per person.
The LEGO brick animal trail is the only one of its kind in the UK and has toured other WWT sites in the UK.
The models were created by south-east based Bright Bricks, the UK’s only certified LEGO professionals, and Tom Poulsom, the LEGO brick ‘birdman’. In total 253,728 LEGO bricks were used to make all 14 wetland characters.
There’s also a wide range of daily talks and feeds at the reserve, a canoe safari and an adventure playground.