Question: I have been on your website, Attracting More Birds at a Glance, and see that some birds eat seed, some eat insects and some eat both. Why can't all the birds eat the same thing? Wouldn't it be less stressful for the birds to be able to eat all types of food?
Answer: First, let's take a look at the anatomy of a bird. The shape of a Yellow-rumped Warbler's bill will allow it to feed on shelled sunflower seeds, but because of its beak it can't break the hull it can't get to the seed by itself. If the bird did swallow the seed whole its digestive system would not be able to grind the seed. But, the good news for the Yellow-rumped Warbler is its digestive system can digest wax myrtle berries and bayberries, which many warblers can't eat.
Shorebirds are another example of anatomy helping them feed. Ducks and Spoonbills feed on the bottom of shallow water. Their bill will strain the water out while keeping the food. If you watch shorebirds carefully their knees are on the back of their legs. Their foot comes forward before their knees do unlike us whose knees lead when we step. This allows their feet to stir the water in front of them, making it easier to grab food with their bill.Hummingbirds are another example of the bill enabling a bird to eat from flowers. The long beak allows them to reach the nectar and some hummingbirds have a curved bill to help them feed on specific flowers. When flying, they developed the ability them to hover since flower petals are too delicate to perch on. Hummingbird feeders, with the small ports, have been developed specifically for this species.
Sparrows have a conical shaped beak which will allow them to crack seeds and their digestive system can grind seeds eaten whole. This allows them to stay in habitats during the winter where insects are scarce but seeds are available. A good mixed seed bird feeder is best for feeding a large variety of seed eaters.
Hawks and eagles have keen eyesight, strong talons and the ability to dive at high speeds. They can see prey from great heights, dive accurately to grab it, and talons strong enough to carry their food away.
Osprey and Great Blue Herons eat the same size of fish, but they feed in different parts of the lake. The heron's feet are adapted for wading and perching so they stay close to the shore. They feed close the surface, thus not competing with other birds mentioned above. The herons swallow their food, fly to the nest and regurgitate to feed their young. Osprey, on the other hand, feed from the deeper parts of the lake, diving to catch fish with legs and talons strong enough to carry the food to the nest.
As you can see, different birds eat different things so there is not so much competition for the food available. Nature has a way to provide for a diversity of species, whether birds or mammals, and the adaptation of their anatomy help them survive. I hope this gives you a brief explanation why some birds eat seeds, some insects, some fish and some have adapted to special foods such as hummingbirds.
If you want to learn more check out the beak of skimmers, crossbills, woodpeckers and more. Then, check out the shape of a bird's feet. OK, I will stop now. As you can see I'm a bit of a nerd about this subject.