Minnesota nongame wildlife specialist Carrol Henderson has written 13 books in his long career at the Department of Natural Resources, a collection rife with outdoors knowledge, bird-watching tips and techniques for bird feeding.

His latest book, “Feeding Wild Birds in America,” still features practical advice on how to increase the variety of species coming to your feeders, but it also details the history of bird feeding in America. It’s one of two bird books released in 2015 that Henderson helped to produce. The other was “Birds of Minnesota State Parks,” written by Robert B. Janssen and published by the DNR.

“Bird feeding helps us build a bond with wildlife,” Henderson said. “Not all people who feed birds in the backyard consider themselves ‘birders,’ but they are to a degree and it’s a major activity.”

According to the latest estimate by the U.S. Fish and Wildlife Service, at least 25 percent of Minnesotans — more than 1 million people — feed birds. Henderson said surveys have indicated that the endeavor is split about equally between men and women in Minnesota and that they annually spend about $175 per person, on average, for bird and wildlife food, feeders, nest boxes and bird baths.

As Henderson’s book points out, backyard bird feeding started as a winter activity. Even into the 1930s and 1940s, enthusiasts pleaded for people to assist birds through cold and snowy winters.

“Sportsmen! Where are you! These birds must be fed or they will perish,” Minneapolis-based Federal Cartridge Corp. said in one campaign from that era. The ammo maker also pleaded with its rural customers to “humanely” destroy feral cats for the protection of birds.

“The abandoned cat, shifting for itself, becomes a killer,” said an ad reproduced in Henderson’s book.

He said bird feeding naturally progressed into spring — to catch glimpses of migratory species — with the marketing of seed and the invention of new feeders. It turned into a year-round hobby out of sheer enjoyment.

Henderson wrote his latest book with Paul J. Baicich and Margaret A. Barker. One of the book’s original findings is the story of how a Cargill agronomist smuggled a bag of about 100 black oil sunflower seeds out of a pioneering Soviet research lab in the 1960s. Those seeds, containing more than 40 percent oil, were propagated by the company and sold into the American market by 1970, according to the book.

The authors also cite a 1980 federal study that was pivotal to modern bird feeding entitled “Relative Attractiveness of Different Foods at Wild Bird Feeders.” The study, conducted in various locations from California to Maryland and Maine, inspired the rise of specialty bird feeding stores based on the knowledge that the manner of food presentation and the type of food set out for birds could attract different species.

For example, chickadees like elevated feeders with small perches while juncos prefer the ground or large platforms. The study’s researcher, fish and wildlife scientist Aelred D. Geis, went as far as setting screens under feeders to see what food the birds were tossing away. In general, smaller, heavier seeds were favored over airy, bulky ones.

Interviewed last week at Cardinal Corner, a wild bird feeding store in West St. Paul, Henderson pointed to an attractive display of open barrels filled with various seeds and seed mixes for purchase by the pound. With a virtual delicatessen at hand, backyard enthusiasts now target certain birds for feeding. Nyjer seed for finches, black-oil sunflower seeds for cardinals, jays and grosbeaks; suet for woodpeckers, nectar for humming birds, white porso millet for buntings and peanuts for chickadees. Safflower, live meal worms and fruits are worked into other mixes, or as stand-alones, but Henderson said a good setup doesn’t have to be complicated.

He recommends four basics: Year-round water, a ground tray with cracked corn and mixed seed, a hanging feeder with black-oil sunflower seeds and a suet feeder.

In an hourlong visit last week to the Mendota Heights home of Karen and Bill Jones, Henderson saw no fewer than 10 species of birds in a carefully landscaped backyard full of feeders. It was an affirmation of his own teaching that the most successful havens employ up to 15 feeders of various types, clustered in groupings of three to four and set at a range of heights. The couple’s backyard also features bird-friendly crabapple trees and an aerated pond.