Lords of the air

An insight into the sophistication of aerial hunters

Predators always arouse our interest whether we see them on TV or in the wild. What is truly amazing about predatory animals is their wide choice of lethal weapons and their varied techniques for catching prey. This article highlights some incredible aerial hunters. The next article will feature land predators, and following that we will review killers of the sea.

A Bald Eagle at Combe Martin Wildlife and Dinosaur Park, North Devon, England, models its powerful beak and keen eye. ADRIAN PINGSTONE

Birds of prey

Birds of prey are birds that hunt for food primarily "on the wing", or primarily during flight. I'm sure that anyone thinking of aerial hunters immediately think of raptors. Raptors is a common name for all majestic birds of prey, which number too many to cover in a single article, as partially evidenced by the graphic to the left.

Today, we will limit ourselves to eagles, hawks, buzzards, falcons and a few others. Their array of weapons is what makes raptors such impressive killers.

The main weapons employed by all raptors are their talons: the sharp, piercing claws on the ends of their scaly feet. A raptor's talons are used to kill or grasp prey and carry it off to a safe eating place. It then uses its hooked, powerful beak to rip apart its catch while pinning it in place with its talons.

Raptors' keen eyesight is also an important part of their arsenal. The ability to spot prey hundreds of metres away gives raptors a huge advantage in the hunt. The prey don't even know they are being hunted, often until it is too late.

Despite having similar weapons, raptors employ very different methods to hunt a wide variety of prey. Eagles are the kings of the raptor world, and they soar on thermals on the lookout for prey. When spotted, a high-speed chase ensues, which often doesn't end well for the preyed-upon animal!

Raptor masters

Eagles soar and glide, which is why they have very broad wings with fingered fringes. Falcons are the opposite, being small and nimble and having narrow, pointed wings for extremely fast flight. Hawks and buzzards are in between in both size and wing shape and aren't as specialised as falcons. They are still superb hunters though! But some are so specialised that they deserve special mention.

Ospreys are extremely skilful hunters. They are a medium-sized bird of prey with a distinguishable spiky tuft on the back of their head. Ospreys are master fish hunters. They are experts at spotting their objectives swimming close to the surface of rivers, lakes and seas.

Once they have locked on to their target, they tuck in their wings and plummet, plunging talon first into the water, thereby piercing the fish. They then manage to get out of the water and fly to a suitable eating place, carrying the huge weight below them.

What is really impressive, though, is that they account for refraction when spotting their prey. Refraction is the phenomenon whereby light bends when it enters a medium with a density different from that of the medium that it is travelling in (e.g., from air to water or from water to air). In such a case, when light reflects off the fish and travels out of the water and into the air, entering the osprey's eye, it bends. This means that its prey isn't actually where it appears in the water, but the osprey accounts for this refraction and aims deeper and in front of where the fish appears to be, with deadly accuracy.

Variations in shape and size of common raptors SHYAMAL

Another legendary raptor is the harpy eagle. It is one of the heaviest, largest, and certainly the most powerful, of the birds of prey. It is also one of the most distinctive looking, with a disc-shaped face and fanned crest on top of its head. It lives in Central and South America, and, unlike other eagles, it doesn't soar high in the sky to find its prey. It lives and hunts under the canopy.

Considering its size, with females having a mass of up to 9kg and a length of a metre from tip to tail, the harpy is a very nimble and fast flier. It can reach speeds of up to 80km/h as it darts in between trees hunting its prey.

An adaptation of the harpy eagle is that despite its size, it has relatively short, stubby wings, but the wings still span 2m! Monkeys, sloths and other tree-dwelling mammals are on its menu, and if they get caught by the harpy's 13cm-long talons, which are longer than a lion's claws, there is little chance of escape. If we humans were any smaller, harpy eagles really would be the creature of our nightmares!

Masters of the night

By day, the eagles, falcons and hawks rule the skies, but by night the owls are in command. A memory that will never leave me is when I worked at a bird of prey sanctuary in Scotland where I helped conduct the owl demonstration. A line of people stand with their eyes shut and are told to say so when they hear an owl fly above their head. They never hear it, and this experience amazes everyone!

The front edges of an owl's wings are fringed or serrated, almost like a torn hem of a garment. This allows the air to move smoothly over the wings, which reduces the woosh sound of rushing air. They can then hunt in near silence, spotting their prey with their superb eyesight and using their powerful legs and talons just like raptors do.

Divers

There is one bird, not a raptor, that deserves a special mention as a hunter. The gannet is a master of the sky, but it hunts under water. When schools of fish swim near the surface in an attempt to evade deeper predators in the water, they are preyed upon from above.

Seeing gannets diving is a lot like watching darts plunge into the ocean. They don't have talons like raptors do, so they use a beak-first method while diving to catch fish, but it is their diving that is spectacular.

They hit the ocean from 20 to 30m above the surface at speeds of up to 100km/h, the momentum taking them 10m deep, but they can swim up to 24m below the surface in their pursuit for fish. They are incredible, specialist hunters.

Personal favourite

My favourite aerial hunter, and in fact one of my favourite animals, is the famous peregrine falcon. Large for a falcon, it is the fastest animal on the planet. During the hunt, it circles at high altitudes until it spots its prey, usually a medium-sized bird, such as a pigeon.

Then it does something simply spectacular. It folds its wings back and goes into a stoop, a dive, head-first towards its prey in a teardrop shape. It is then that it breaks records, hitting speeds of well over 300km/h! The impact of the peregrine's talons is often enough to kill its prey instantly, and the prey is then devoured. A bird that is faster than a Ferrari? That's why it is my favourite.


Dave Canavan has an MSc in Behavioural Ecology and is the Head of Secondary at Garden International School. Dave is fascinated by science and loves animals, especially the dangerous kind! You may contact Dave at davidc@gardenbangkok.com.

About the author

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Writer: David Canavan
Position: Writer