A bird’s beak, or bill, is not just for gathering food. They can be used for grooming, fighting, courtship display, feeding young, nest-building, manipulating objects and even regulating temperature. All in all, beaks are quite the multifunctional tool.

Here are some of the world's more bizarre beaks and their specialisations.

Toco toucan (Ramphastos toco) by Anna Kwa

The toco toucan’s impossibly showy beak constitutes one-third of the bird's total length. But it is not just for show, this multi-purpose appendage can be used to collect and skin fruit, frighten predators, attract mates and defend territory. Recent research has also shown that it also helps to keep the bird cool in the heat of the tropical day.

Anna took this superb example just after the toucan had been happily chasing butterflies. See Anna’s original image on Flickr.

Oriental pied hornbill (Anthracoceros albirostris) by Chan Boon Hong

It would be difficult to miss this mighty beak, which has to be supported by powerful muscles and fused vertebrae. It is used to catch prey, fight and preen. However, the most recognisable feature of most hornbills is the hollow structure along the top of the bill, called a casque. This reinforces the beak and may be used by males to fight, attract females and resonate sound.

Chan photographed this Oriental pied hornbill in Singapore when it perched just 5m away from him. He said, “I'm lucky to have a close encounter with this beauty.” Chan’s original image is on Flickr.

Bald eagle (Haliaeetus leucocephalus) by Claudia Daniels

The wicked-looking beak of the bald eagle is typical for a bird of prey: it is strong and sharply curved for tearing flesh into easy-to-swallow chunks from fish, mammals and other birds. These beaks can also pierce and remove fur and feathers from prey.

This eagle flew out of the nest and landed very close to Claudia from Venice in Florida, “I just had enough time to point my camera at its head before it flew away,” she said. Here is Claudia’s original on Flickr.

Sword-billed hummingbird (Ensifera ensifera) by Richard Orr

The sword-billed hummingbird's beak is remarkable because it is longer than the rest of its body. The extraordinary length of the hummingbird's beak and tongue, are adaptations to feeding on nectar from flowers that have long petals, such as species of passion flower. It is a nice example of co-evolution.

Richard photographed this individual on a foggy day in the Reserva Yanacocha, Ecuador. See Richard’s original image on Flickr.

Dalmatian pelican (Pelecanus crispus) by Christian Brysch

There are big beaks and then there are pelican beaks.

Pelican feed almost entirely on fish that they scoop out of the water into the enormous throat pouch – the water is then drained out and the fish swallowed. The hook at the end of the top mandible is used to spear fish, which are tossed into the air before being swallowed.

This Dalmatian pelican was captured by Christian Brysch at Lake Kerkini in Greece when it landed on the edge of a fishing boat. See Christian’s original image on Flickr.

American flamingo (Phoenicopterus ruber) by Steven Reynolds

It's a flamingo's one-legged stance that it is widely famed for, but flamingo beaks are equally remarkable. Unlike most birds flamingos filter feed, in a similar manner to whales.

When filtering, a flamingo's head is held upside down in water for long periods, and consequently the jaw is reversed with the lower bill larger and stronger than the upper one.

Steven Reynolds took this image in wetlands outside Orlando, USA. “Because of their long necks, interesting beaks and continual preening, the birds take on many interesting and varied shapes,” he said. Here is Steven’s original image on Flickr.

Red-necked avocet (Recurvirostra novaehollandiae) by Heather Thorning

All four species of avocet have peculiarly shaped beaks that are long, thin and curve upwards. They sweep these slender bills from side to side, skimming mud and surface water. This action stirs up small invertebrates and the birds then use their beaks like tweezers to pick out individual prey.

This red-necked avocet was photographed by Heather feeding in a waterhole in Western Australia, a popular location for waders. See Heather’s original image on Flickr.

Southern yellow-billed hornbill (Tockus leucomelas) by Rob Weaver

The formidable-looking, heavy beak of this hornbill is used to forage for seeds, small insects and spiders on the ground. The birds then jerk their head to toss the food to the back of the throat. In this species, the casque on the top mandible is not as obvious as in many other hornbills, such as the Oriental pied hornbill above.

Rob captured this one on Canon 40D camera in Botswana in February 2015. See Rob’s original image on Flickr.

Spoonbill (Platalea) by Mohammed Swidah

The shape of a spoonbill's beak shouldn’t come as any surprise. They wade through shallow water, stirring up mud and debris, swinging the partly open beak from side to side through the water. When the long, flat, spatulate bill touches prey it snaps shut, before the prey is pulled from the water and swallowed.

This feeding behaviour was beautifully captured by Mohammed in Jeddah, Saudi Arabia. Here is Mohammed’s original on Flickr.

Black skimmer (Rynchops niger) by Jerry Swain

The large and unequal red and black beaks of the skimmers are both unusual and unique. The skimmers fish by dragging, or skimming, the longer lower mandible through the water as they fly low and fast over the surface of shallow water. The lower mandible snaps shut on any small fish that are caught.

There are three species of skimmer. This black skimmer, on the beach at Fort Pierce, Florida was taken by Jerry Swain who was initially looking for an oystercatcher: “I found a wide variety of shore/sea bird species but did not find an oystercatcher that day,” he said. See Jerry’s original on Flickr.

Red crossbill (Loxia curvirostra) by Tony Varela

Crossbills have one of the most peculiar and specialised beaks in the bird world. The crossed bill tips may look odd, but it is in fact a clever adaptation to getting seeds out of closed pine cones.

The bird inserts the tips of its bill under a cone scale and bites down. The result is that the scale is prised open, exposing the seed. Interestingly, each species' bill shape is optimised for opening seeds from different species of conifer.

This red crossbill image was taken by Tony in his garden in Washington, USA. See Tony’s original image on Flickr.

Australian pelican (Pelecanus conspicillatus) by Eve Boulanger-Grondin

Pelicans have some of the longest beaks in the avian world, with sizes approaching half a metre in length. Acting like a net, a pouch can hold up to 13 litres of water.

When not feeding, the enormous pouches are folded and can be quite colourful, particularly during the breeding season.

Eve took this photograph on a trip to a water park in Bali, Indonesia. She told BBC Earth, “They were very easy to approach so it was a nice opportunity for me to photograph them.” Here is Eve’s original image on Flickr.

Long-billed curlew (Numenius americanus) by Mick Thompson

As far as long thin bills go they don’t get any more impressive than the curlew. The remarkably long and slender beak curves downward and is the perfect adaption for probing mudflats, and very soft ground, for worms and other invertebrates. The beak can measure 20 cm or more in length.

This fine example of a long-billed curlew was taken after sunrise by Mick in wetlands where the San Diego River empties into the Pacific, just a few miles from downtown San Diego, California. See Mick’s original image on Flickr.

Collared aracari (Pteroglossus torquatus) by Jim Cumming

The large showy beaks of aracaris, like all toucans, look very heavy and not suitable for flight. They are, in fact, extremely thin and aerodynamic, re-inforced with a crisscross of lightweight rods made of bone. The widely spaced tooth-like protrusions on the upper mandible of the collared aracari help them catch and grasp fruit.

This image was taken by Jim in Costa Rica. “We just watched a small flock pig out on bananas,” he said. See Jim’s original in Flickr.

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Thank you to all the photographers who gave BBC Earth permission use their images.