Birds have many food sources on this earth, which range from the smallest of seeds, plants, eggs, fish, mammals, carrion and even our garbage. I can’t think of one food source birds don’t try to eat.

Some birds have adapted to get to their food, from diving birds with specially adapted feathers and eyes to locate their prey to nectarivore birds with specially adapted bills and tongues for extracting nectar. Birds have evolved many strategies to find and eat food – today’s article highlights these.

Conventional Diets

Birds’ diets vary significantly from species to species, but we will look at a few “normal” diets. Not just at the diet but some strange adaptions some species have in feeding.

Granivores (Seedeaters)

Seedeater’s main diet would be seeds or grains. Most are small birds with short, solid bills, specially adapted to remove the seed’s husk and eat the nutritious kernel.

A few seedeaters, such as doves, have slender bills which allow them to swallow the seeds whole. They have crops and gizzards, which help process the whole seeds.

Seeds are carbohydrates, so some seedeaters supplement their meals with protein-rich insects. The seeds have little water so that you will see the seedeaters around water a lot, drinking.

Seeds are harder to come by in the drier areas, so most seedeaters there are nomadic.

Insectivores (insect eaters)

Insectivores eat a whole selection of protein-rich insects and consume Invertebrates such as spiders, worms, and molluscs. Unfortunately, these insectivores have diminished considerably over the last few decades because of the amount of pesticides and fertilisers we use.

Insectivores have a range of bills, from the slender probing bills of the wrens, tearing bills of the shrikes and the broad bills of the nightjars. One of the interesting Insectivores is the woodpecker, with their hard pointy bills made for boring into wood and long tongues adapted to searching for insects. 

Frugivores (fruit eaters)

Frugivores feed mainly on fruits and have substantial, robust bills that allow them to break the hard shells of some fruits and open tough skins. The examples we have are peeling bills like that of the parrots and toucans, which can peel off any outer layers of the skin so that they can get to the juicy part of the fruit. The picking type bills, much like waxwings, are used so that they can pick small fruits. The slicing type bills, like the orioles, can slice through large fruit to get to the seeds and flesh of the fruit.

The one significant bit of information is that most fruit eaters have very short intestines, which allow the seeds to disperse quite soon near the original tree so as not to be too far away into a hostile environment for these trees.

Raptors

Most raptors are carnivorous, and each species is designed to hunt specific types of prey, including mammals, fish, reptiles and birds. Their bills are generally sharp and hooked to tear through the meat of their prey. They have keen eyesight (binocular), sharp claws and strong legs.  Wing types for types of raptors are,

• Huge finger-like wings for soaring. (eagles, vultures and hawks)
• Shorter, broader wings for chasing birds through trees (goshawks)
• Long tapered wings for speed to catch birds in flight. (falcons)

Scavengers

Scavengers like the Vultures and Marabou Stork are seen mainly soaring at great heights, looking for dead carcasses to feed on. The task of the scavengers is vital for cleaning the carcase from the environment. Because their form of food is scarce, they have been adapted to soar for great distances from their nests on thermals.

The unique thing about Vultures is that they have a specific pecking order:

• The Lappet Face Vulture is the biggest, with solid bills to tear open any carcass and eat the bowels. They soar lower and keep the other species at bay. 
• The White-headed Vulture also has a strong bill. Their tongues have backwards-facing spines that help them remove the meat from the bone, and they usually fill their gizzard exceptionally quickly.
• The Hooded Vultures are the smallest vultures with narrower bills to peck the remaining meat on the bones. They have been known to eat the faeces of lions and hyenas to get nutrients and minerals. The faeces also contain bile salt, which helps their digestive system.
• The Marabou Stork tends to follow the vultures around and lives off the scraps. They are also known to eat the faeces of carnivores. They will also eat nestlings of other smaller birds.

Unusual Diets

Here, we begin an exciting part of the article: unusual diets and the species that eat them. Also, there are ingenious methods that some birds use to extract their food.

Hoatzin – Leaves

The Hoatzins are found in South America and are clumsy, slow-moving, strange-looking birds that primarily eat the leaves of plants and trees. They are one of the only birds in the world that does this. It has a specially designed stomach that will break down all the greens and ferment them. The Hoatzin’s meal can take up to 45 hours to pass through their bodies.

They have serrations on their beak to cut the leaves into smaller parts so they can swallow them.

Vampire Ground Finch – Blood

The Vampire Ground Finches are small brown birds with thick, sharp beaks. They are found in the Galápagos Islands. These birds need to adapt to the harsh conditions there. During the winters, they usually feed on blood from the larger birds, but after the rain falls, they complement their diet with plant and animal matter.

The Vampire Ground Finch mostly eats the blood from the Nazca Booby and Blue-footed Booby, who do not seem to mind.

Egyptian Vultures – Eggs

Egyptian Vultures usually eat mostly anything from carrion to scavenging at rubbish dumps. One of the vulture’s favourite foods is ostrich eggs. Now, these ostrich eggs are enormous and robust; they even take the weight of a fully grown human.

The vulture does something that no other bird can. It picks up big stones with their bills and keeps dropping them on the egg until it breaks. It only chooses a stone that will break the top, so it is not too heavy to break the whole egg. What a feast it has, once opened—scrambled eggs for breakfast.

Bearded Vulture – Bone and Marrow

The Bearded Vulture (Lammergeier) is the only bird species adapted to eat bones and marrow, which is over 80% of their diet. Their stomach acid is so strong that it helps dissolve the bone in under 24 hours. They want to eat the marrow and fatty bone first, which is faster to digest.

They can swallow a piece of bone as long as 20cm. If the bone is too long, they will take to the skies and drop these bones with great accuracy onto rocks to break them.

Honeyguides – Beeswax

Honeyguides have a particular enzyme to help them digest beeswax, which forms a large percentage of their diet.

Although their skin is a bit thicker, especially around their eyes, they have been known to be killed by a swarm of bees protecting their hive.

Honeyguides, when they find a hive, battle to break into them. So, they try and get help from humans or honey badgers. They do this by trying to get the attention of their “helpers by calling out, flicking their wings and getting the “helpers” to follow them to the nest. Once the hive has been broken, the honeyguides feed on the wax.

Palm-nut Vultures – palm nuts

The Palm-nut Vultures are the only vultures that eat the fruit of the Rafia Palm Trees. They would fly into the side of the palm tree and grip a bunch of ripe fruit, carry them to a perching spot and, with the help of their claws and bills, remove the fleshy parts of the nut and drop the kernel once satisfied.

Bat Hawks – bats on the wing

The Bat Hawks typically feed on insectivorous bats. They are not very successful with the larger fruit bats.

The hawks can be seen near a bat colony near dusk. Once the bats swarm out, the hawks get to work. They usually catch one bat every 3 minutes on the wing. The hawk’s hunger needs are met within half an hour. It has been said that their catching rate per attempt try is about 50%, depending on the season.

New Caledonian Crow – Sticks to catch prey

The New Caledonian Crow is endemic to the Caledonian Islands in the Pacific. Crows are widely acknowledged as being the most intelligent birds in the world.

These crows use bits of vegetation, primarily barbed, and probes into crevasses to catch insects or grubs. They agitate the prey until they bite the stick, and the crow pulls them out. Sometimes, the crows create a hooked twig and impale the larvae or grub.

Honey buzzards – Wasps and Bumble bees

The honey buzzards are relatively passive and spend time perching and watching the foraging patterns of wasps and bumble bees. Once found, they will dig out the nests and consume the larvae. They walk on the ground for some distance, foraging for wasps and hornets.

They have scale-like small overlapping feathers around their eyes that protect them from wasps and bee stings. They are also swift and agile, which could help them dodge a few wasps when needed.

In Africa, they will be found digging out paper wasp nests from eaves and consuming the larvae.

Cuckoos- Hairy caterpillars

The cuckoo’s favourite foods are fat, hairy caterpillars. As we know, when mistakenly picking up a caterpillar, we get a horrible itch or aggravation. The cuckoos do not experience any of these, although their stomach gets lined with these irritating hairs. What an extraordinary diet.

Crossbills – Conifer seeds

The amazing crossbills are usually found in the Northern Hemisphere, and you will find them feeding in the Coniferous Forest as they extract seeds off these conifer cones. They have these very unusual sharp crossed bills. (mandibles)

What birds eat to help them digest

Grebes

Grebes are known to swallow their feathers and feed them to their young. They accumulate between the gizzard and the stomach.  This is so food digestion slows down and stops sharp fish bones from travelling further. They then regurgitate these balls together with indigestible parts of their prey.

Ostrich

Ostrich have no teeth, so they need assistance to help break down and grind the food before digestion. They consume stones and grit for this purpose. Stones remain in their gizzard, but these become relatively smooth over time, so they swallow grit to help.

Conclusion

The human population is growing, so more and more natural forests and grasslands are being decimated. This means the population of insects, fruit, fish, mammals, reptiles, and all that birds feed on is an ever-changing challenge.

Birds have an extraordinary diversity of feeding strategies, which are essential cogs in ecosystems for helping disperse seeds, keeping ecosystem trophic levels in check, reducing disease, and ensuring nutrients cycle effectively in our natural world. That’s why it’s important to protect birds and the habitats they are part of – because of their crucial role in driving and shaping ecosystems, which ultimately affects human well-being and food security (e.g. through farming).