We all have dietary concerns to be aware of, from food allergies and sensitivities such as lactose intolerance and celiac disease to high blood pressure, diabetes, high cholesterol, and other conditions that are directly affected by diet. But what about birds? A new study has recently explored the idea of cholesterol in birds’ diets, particularly urban and suburban birds, with interesting results.
High Cholesterol Is Bad – Isn’t It?
The study, conducted on rural and urban crows in California and New York, involved supplying cheeseburgers to the birds as part of their typical foraging, then measuring both the birds’ cholesterol rates as well as their survival rates in different habitats. Urban birds that did not have the extra cheeseburgers in their diets still had higher cholesterol than their rural cousins, likely due to crows’ dumpster-diving habits and a greater availability of high-cholesterol foods in their vicinity. Foods such as fries, cheese, chips, and processed meats like hot dogs, bacon, and lunchmeat are all high in cholesterol and more readily available as scraps to urban birds.
Surprisingly, young birds in urban areas, while they did have higher cholesterol, also had better body condition than rural youngsters. That measurement is not precise, however, since body condition only measures a bird’s weight, and not its overall muscular health and fitness. A fat bird, then, would typically be rated as having better body condition than a thin bird, but little else is known about its whole fitness.
The survival rates of both rural and urban crows was more difficult to measure, and in general urban nestlings had lower long-term survival rates and shorter lifespans. There are many additional factors involved, however, including window and vehicle collisions, predators, and other threats. It may not be the higher cholesterol dramatically impacting the birds’ survival rates, but additional study is recommended to further pursue this investigation. It also must be noted that, in humans, the most severe long-term effects of high cholesterol do not appear until later in life, and this study did not include elderly birds that may have had less healthy diets throughout their lives.
Read more about this bird dietary study in National Geographic,
or examine the full study in The Condor.
Diversity is the Best Diet
Regardless of our own dietary needs and preferences, one good, general piece of advice is backed up by scientific and medical research: diversity. A diet that includes a variety of fruits, vegetables, grains, and proteins is always better than a more restricted, less diverse diet. The nutritional composition of different foods, including fiber, sugars, protein, vitamins, and minerals, is essential for overall good health.
But what about birds, which seem to eat very restrictive diets? While humans regularly vary their menus, it seems as though birds favor the same foods over and over – picking through birdseed for the best morsels, visiting and revisiting the suet feeder, and draining the nectar feeder of every sweet sip. Aren’t those more restrictive diets dangerous for birds?
In fact, a bird’s diet is far more diverse than we realize. While it seems like backyard birds eat only the seeds in our feeders, most birds get just 10-15 percent of their daily meals from feeders. The rest of their food is naturally foraged, and may include a wide variety of seeds from different plants, a range of different insects, nectar from many different blooms, and all types of different fruits, buds, and berries. Even raptors that consume only live prey or carrion have good variety in their diet, as the different prey animals they consume will have different nutritional compositions and nutrient densities. Furthermore, a raptor consumes nearly all of an animal it hunts, including the muscle, organs, skin, tendons, and other bits, all of which have different vitamins, minerals, and nutrients.
Providing Birds a Better Diet
Just as we can help our own diets by incorporating different foods, trying new recipes, and enjoying a diverse diet, we can also help our backyard birds by offering a wide range of foods for their dining pleasure. A feeding station that offers more types of birdseed and different grains – sunflower, safflower, millet, milo, cracked corn, Nyjer – along with suet, jelly, nuts, orange slices, nectar, and other popular foods will satisfy birds’ nutritional needs more fully. Furthermore, a greater variety of foods will also attract a greater variety of birds, all of which will select which foods they prefer from the better buffet. Natural foods in the yard, including nectar-rich flowers, seed-producing blooms, fruit trees, pine cones, and healthy insect populations, will further provide dietary diversity to birds and attract even more species.
This isn’t to say that the occasional treat should be avoided. I love certain types of chips, but I don’t eat them all the time. I have my favorite candy bars as well, but they aren’t the only desserts I enjoy. Birds, too, can have occasional treats, but just as we need to understand that birds are only getting a fraction of their diet from our feeders, only a fraction of their treats come from our hands as well. Many birds – not only crows as in the study, but also gulls, sparrows, doves, jays, and many other species – will snack on trash and leftover tidbits from picnics, campgrounds, sports arenas, fast food bags, and parking lot spills. Birders in urban areas should especially be aware of that foraging, and limit extra treats they may offer at their feeders.
Ultimately, the same advice we’ve heard all our lives – a diverse diet and all things in moderation – applies to feeding the birds as well as to our own nutrition. Bon Appetite!