Most birders pick up a pair of binoculars to appreciate an avocet or raven. Nicky Fijalkowska takes a different tack: She grabs a pair of needles and a ball of yarn. The United Kingdom-based knitting designer has a knack for turning endless strands of wool into mini replicas of birds. The members of her growing aviary include puffins and owls, and they owe their finely stitched field marks to a lifelong obsession. Growing up, Fijalkowska would sketch birds in her parents’ garden and take trips with the Young Ornithologists’ Club. Knitting, on the other hand, didn’t come so naturally. “I tried it as a teenager, but I always made clothes that never fitted and I ended up hating,” Fijalkowska says. She didn’t pick up her needles again until her late 30s, after swine flu and post-viral fatigue kept her bedridden for a year. “Some days I didn’t have the energy to do anything,” she says. “But I taught myself to knit and was able to build things...