Deborah Robbins Millman is the director of Cape Wildlife Center, one of New England's largest wildlife rehabilitation centers and a leader in rehabilitating endangered and threatened New England species. She contributed this article to Live Science's Expert Voices: Op-Ed & Insights

For many, feeding birds at ponds and parks is a cherished childhood memory; one they lovingly recreate for their children and grandchildren. Yet tragically, thousands of birds die annually due to a condition overwhelmingly caused by people who don't know this beloved activity can be deadly.

"Angel wing" is a deformity commonly found in ducks, geese, swans and other waterfowl. There has been little scientific study done on the condition, yet most wildlife and waterfowl experts agree the overwhelming cause of angel wing is an unhealthily high protein and/or carbohydrate-based diets. The disorder causes the last joint in one or both wings to unnaturally twist outward, rather than lie flat against a bird's body. 

Birds with angel wing are stripped of their ability to fly, and therefore their main method of defense. Since the affected birds are unable to escape predators, they are often maimed or killed by them. Additionally, when life-threatening weather conditions develop, they are unable to fly away to safety, and instead starve, succumbing to injuries or freezing to death. 

The birds most likely to contract angel wing are those residing in parks, on ponds and in public areas where people feed them unhealthy food. Because birds grow much more rapidly than humans, each day's nutrition has a direct effect on development. Even a few days of improper eating can cause irreparable damage. Research, such as oft-referenced studies on Canada geese and nutrition for young birds, suggest feeding waterfowl an unhealthy diet can accelerate growth, causing the wing to develop too quickly for proper bone support. 

Nutritious waterfowl feed or duck pellets are inexpensive, easy to carry and can be purchased at most feed stores. Seedless grapes cut in half; shredded kale; Swiss chard or romaine lettuce; and grains, including wheat, barley and oats, are all healthy food sources that will appeal to most waterfowl. (Make sure anything you feed is bite-sized, to avoid choking hazards.) [Wild Animals Suffer on 'Junk Food' Diets ]

Cape Wildlife Center, our wildlife rehabilitation center based in Barnstable, Mass., and operated by The Fund for Animals (an affiliate of The Humane Society of the United States) treats about 2,000 animals per year, including a significant number of geese, swans and ducks suffering from angel wing. The highest incidence of admission is late fall or winter, when affected birds have grown enough for the condition to be fully and painfully apparent.

If you're a topical expert — researcher, business leader, author or innovator — and would like to contribute an op-ed piece, <a href=mailto:expertvoices@techmedianetwork.com>email us here</a>.
If you're a topical expert — researcher, business leader, author or innovator — and would like to contribute an op-ed piece, email us here.

If the patients treated are very young, the condition can sometimes be minimized by splinting and repositioning the affected wing while feeding the birds a proper diet for optimal growth. Even then, a full recovery is not guaranteed. For rehabilitators, it can be emotionally taxing to see birds denied the chance for a full and productive life because people didn't know about the dangers of improperly feeding them.

Angel wing can be drastically reduced by not feeding birds "people food," including white bread, popcorn or crackers. This simple rule will literally save lives. (Angel wing chiefly affects waterfowl. Young songbirds are fed by their parents, and after they fledge, have a lot of mobility and exposure to a varied diet.)

The risk of birds developing this disease doesn't mean the enjoyable and bonding activity of feeding birds must be eliminated — you just have to identify areas where feeding waterfowl is supported. Typically, places that do not support feeding have posted signs, or are located on private property, and offer the birds the right food to sustain their health.

Feeding wild birds a proper diet preserves a treasured family tradition while teaching children the importance of making choices that strengthen, rather than undercut, the human-animal bond. In this way, we will rear generations of people recognizing the necessity for responsible stewardship and celebrate the value of compassionate co-existence with wildlife. 

Follow all of the Expert Voices issues and debates — and become part of the discussion — on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher.  This version of the article was originally published on Live Science.