The artwork belonged to Bill Makins, a farmer who founded Pensthorpe Natural Park near Fakenham with his wife, Francesca.
Mr Makins, who died in 2022 aged 90, had a passion for waterfowl and wading birds, and created the park to be an area for the animals.
The park grew into one of Norfolk’s leading visitor attractions and provided a conservation sanctuary for rare bird species and other wildlife.
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For over 45 years, the couple collected some of the finest examples by the best ornithological artists of the 20th century.
Mrs Makins said: “Having created Pensthorpe Park, conservation continued to dominate Bill’s life, from his choice of garden plants to encourage birds and insects, to art to hang on the walls, to give us pleasure.
“It is with great reluctance I am selling our wonderful collection, but widowhood necessitates a smaller home and being unable to select one painting above another I decided to sell them all.
“I sincerely hope that these paintings give as much pleasure to their new owners as they have given Bill and I over the years.”
The collection, which features works from John Cyril Harrison, Frank Southgate, Roland Green and George Edward Lodge, will be sold by Cheffins Fine Art.
Luke Bodalbhai, a paintings specialist at Cheffins, said: “John Cyril Harrison, who lived and worked in Norfolk, is particularly well represented, likely due to Bill’s appreciation of his unerring skill at capturing birds in flight.
“Their enthusiasm for conservation evidently extended into art, as all the works on offer are also extremely well preserved.”
The pictures will be offered as part of The Fine Sale on March 26.