A smorgasbord for the birds!

Text and photographs Dave Rimmer

One of my earliest birding observations is that you seldom, if ever see either an underweight or overweight bird in a single species flock – they all look pretty much the same size (except in the case of sexual dimorphism). And that has all to do with what they eat, and unlike many of us it’s about eating a well-balanced diet. That said, we at least have a bit of variety in what we eat – imagine just having to eat seeds all day!!

With an excess of 10,000 bird species worldwide that have adapted to exploiting virtually every conceivable niche of the global environment, birds have evolved and adapted to many different methods as well as a wide variety of sources to acquire food to sustain them. As a consequence, the variety of feeding methods and food sources has required adaptations / modifications to the structure of the bill which is why we can observe long, short, hooked, decurved, recurved, conical, notched / toothed, tubular, shovel-shaped, spear-shaped, etc. bills to name just a few.

What do birds feed on?

Birds consume a wide range of both plant and animal matter with each species having developed specific structural and behavioural adaptations to take advantage of a particular food type preference. Birds that generally feed on specific food sources can be grouped according to their dietary preferences, some of which are more commonly known but if like me one or more of these may certainly be new to you.

I must hasten to add, that although numerous species are mentioned in the groupings to follow, it does not mean they’re assigned exclusively to that food category. Most birds eat a varied diet and thus fit into one or more of the listed dietary preferences.

1. Granivore (seeds)

Many an urban garden has a seed tray at which are attracted the likes of Waxbills, Sparrows, Weavers, Mannikins, Bishops, Canaries, Widowbirds, Whydahs, Indigobirds, Firefinches and if you’re really lucky a Twinspot.

An iconic Kloof garden species, the beautiful Green Twinspot.

A male Blue Waxbill.

A grass seed feast fit for a Yellow-fronted Canary.

2. Nectarivore (nectar)

In this group you typically find the Sunbirds, Sugarbirds and Hummingbirds (sadly not a species found in Africa) with their fit for purpose slender, pointed, decurved bills which derive their energy and nutrient requirements from a diet consisting mainly or exclusively of the sugar-rich nectar produced by flowering plants.

Cape Sugarbird, a bird strongly dependent on protea nectar.

Collared Sunbird, probably more insectivorous than other sunbirds.

An Orange-breasted Sunbird feeding on an Erica spp.

A Greater Double-collared Sunbird, endemic to Southern Africa, feeding on an Aloe spp.

3. Insectivore (insects)

This group is represented by more than 6,000 of the world’s species, and in which we typically find the Drongos, Flycatchers, Bee-eaters, Robin Chats, Swallows, Warblers, Cisticolas, and Boubous which feed mainly on insects, spiders and other invertebrates.

The Spotted Flycatcher is a non-breeding migrant that feeds on insects, and occasionally small fruit.

African Paradise-flycatcher (female), a delight to have a pair of these flitting about in your garden.

The Southern Black Flycatcher – a common Kloof garden bird and not to be confused with the Fork-tailed Drongo.

A pair of White-fronted Bee-eaters sharing a moth.

The smallest bird in this particular genus, the Little Bee-eater.

A White-browed Robin Chat with a tasty morsel – a small grub of sorts.

A mouthful of Odonata spp. for the chicks of this White-throated Swallow.

Dark-capped Bulbul being mindful of the sting on the end of its meal.

4. Frugivore (fruits)

Frugivorous describes a diet that consists primarily (though not necessarily exclusively) of fruit, including tree fruits as well as berries. Species that fit this group are the Turacos, Bulbuls, Orioles, Barbets, and Hornbills. If only monkeys weren’t so prolific along the KZN coastal belt, I’m sure lots of people would have fruit trays in their gardens to attract these wonderful fruit eating birds.

A common bird found in Kloof gardens, the Purple-crested Turaco.

An Acacia Pied Barbet with only the pip remaining from the fruit it has just finished eating.

A Crested Barbet feeding on an apple found in the children’s play-ground.

5. Piscivore (fish)

While the term carnivorous refers to any general meat diet, more specific variations where a predator consumes only a specific type of meat have more specialised terms. In this case, piscivorous (fish-eating) species include the Penguins, Herons, Egrets, Darters, Ospreys, and the African Fish Eagle.

The largest species in this genus, the Goliath Heron with a meal to match his appetite.

Once you have heard the cry of the African Fish Eagle, you will always come back to Africa.

Unlike his larger cousin, this Squacco Heron is catching small fry.

6. Herbivore (plants)

Few birds are strict, consistent herbivores, but those that have largely herbivorous diets include the Whistling Ducks, Teals, Geese, and other large waterfowl.

In water, the White-faced Whistling Duck dabbles with its head immersed or by up-ending itself and diving for food.

The African Pygmy Goose forages on seeds and flowers of water-lilies, and aquatic plants.

7. Carnivore (meat)

Birds of prey such as Hawks, Falcons, Eagles, Vultures, and Owls are familiar carnivorous birds, but many other types of birds also consume a fair amount of meat and could be classified as carnivores.

A Black-winged (shouldered) Kite devouring a freshly caught field mouse.

8. Omnivore (meat and plants)

Omnivorous birds eat a wide range of different foods, with both plant-based (e.g. seeds, grain, grasses, nectar, fruit, nuts, flowers, leaves, buds, roots, pollen, sap) and animal-based (e.g. insects, fish, lizards, crustaceans, mollusks, rodents, snakes, mammals, eggs) materials being significant parts of their overall diets. Birds known to have omnivorous diets that are more equally balanced between plant- and animal-based foods include Woodpeckers, Thrushes, Bustards, and Korhaans.

The diet of the Blue Korhaan consists mainly of insects, small reptiles and vegetable matter (grass seeds, flowers and other leaves).

9. Folivore

A folivore is an herbivore that specialises in eating leaves. Mature leaves contain a high proportion of hard-to-digest cellulose, less energy than other types of foods, and often toxic compounds. Our best-known example that fits into this food group are the Mousebirds. Ever wondered why they have a dark-skinned fluffy tummy and spend long hours exposing it to the warm rays of the sun? It is believed that by “heating” their food, it aids in the digestion process of the leaves eaten.

This Red-faced Mousebird is collecting nesting material, but normally feeds on new leaves, shoot tips, fruit and also nectar from Aloes.

10. Sanguinivore (blood)

This group is not for the squeamish or faint-hearted as it is reserved for the blood-suckers. Oxpeckers eat mostly ticks, blood and mucous, and “frequently feed at wounds on an animal, seemingly keeping wounds open and encouraging blood flow.” (Roberts v. 7)

Is this a sit-down meal or running buffet? Red-billed Oxpecker with a plate full of ticks to dine on.

11. Saprovore (dead matter)

Among the largest birds of prey, most Vultures live by scavenging from animal carcasses.

The remains of an elephant carcass receiving the attention of an Egyptian Vulture and its close look-a-like the Hooded Vulture.

Bizarre appetites

Birds may include items in their diet which would not ordinarily be considered food. This is often a response to nutritional stress whereby minerals lacking in their diets are occasionally procured from alternative sources. This may explain to those that have ever witnessed birds feeding on dust (African Green Pigeon), stones to assist with digestion (Rock Pigeons and Ostriches), bone or bone-related material (Bearded Vulture) as well as calcified animal droppings, egg-shells and snail-shells containing elements of calcium and phosphorous.

And then believe it or not, you get the opportunists, like herons plucking quelea from the air as they fly past a water hole as has been witnessed by some in the Kgalagadi, or this Striated (Green-backed) Heron that thought the Malachite Kingfisher perched alongside it would make a tasty morsel.

Was it catch and release, or an opportunistic meal? – the outcome was not observed!

Photo: Tyron Dall

Or this Woolly-necked Stork that took as much as 10 to 15 minutes to toss, position and then ingest a dead Thrush it found in my garden a few years back.

Not the ordinary everyday meal for this Woolly-necked Stork.

Author photo: Pat McKrill

About the author

Dave was born and raised on a tobacco farm in Zimbabwe, schooled in Harare and studied Geography at Rhodes University. Having subsequently obtained a Postgraduate Diploma in Agricultural Engineering from Silsoe College (UK) he focused his career in the water and sanitation sector with stints working in Namibia, the CSIR in Pretoria and then moving to Durban in the late 90’s. It was not until about 2007 when visiting Hluhluwe Game Reserve a few hours before a workshop that he developed an interest in birds.

His birding travels have included the occasional visits to Zimbabwe and Mozambique, and numerous local family / birding holidays which helped him reach a target of over 700 bird sightings. More recently he has turned his focus to bird atlassing and is a valuable contributor to the Southern African Bird Atlas Project and other Citizen Science projects. He currently runs and operates Kingdom Birding. Follow him at https://www.facebook.com/KingdomBirding for more information.