Different wader species have their own unique ways of finding food, and each bird has a special tool to match – their bill. Here, we explore the fascinating capabilities of some of our waders’ incredible bills.
Adaptable Oystercatchers
The oystercatcher’s loud, red-orange bill contrasts proudly against the bird’s monochrome plumage, which is befitting when you consider its stand-out capabilities. Molluscs are oystercatcher’s food of choice, and birds take individual approaches to extracting a mollusc’s fleshy innards from its tough outer shell.
When eating mussels and cockles, some birds will force the tip of their bill between the two shells and lever them apart in a swift twisting motion, while others will simply hammer away until they’ve made a hole that allows them to access the soft insides.
Once in, they use their bills like scissors and slice through the mollusc’s adductor muscle, which holds the shell shut. An oystercatcher’s bill adapts to its preferred method – birds that prize shells open have a laterally compressed bill that they can wedge between two shells, whereas the bills of birds that hammer away at their prey are heavy and blunt.
All of this work results in a lot of wear and tear, but the oystercatcher’s bill grows so quickly (around 0.4mm a day – much faster than human fingernails) that this is counteracted. They can also be left or right ‘handed’, striking their bill from either the left or the right.
Clever Curlews
Curlews are renowned for their spectacularly elongated, crescent shaped bills – the unusual shape is even referred to in their Latin name, Numenius, which translates as ‘new moon’.
It’s possible that this curvature makes it easier for the curlew to access hard to reach places like worm burrows. If you watch a curlew foraging, you may see them twisting and turning their heads in an effort to extract their prey from awkward places.
The tip of the curlew’s bill is slightly enlarged and packed full of nerves that are highly sensitive to pressure, which means that they can detect the slightest of movements, including bubbles emitted by prey animals – a fatal giveaway as to their location. It’s thought that they may even be able to detect where creatures are hiding based on pressure waves felt when they plunge their bills into the mud; any obstacle would alter the pressure at a specific point, directing the curlew to its next meal.
Sharing the shore
As well as being individually fascinating, our shorebirds have collectively evolved different lengths of bills, so they are able to feed at different depths. This clever co-adaption means that they are not in direct competition with each other, which is why you will often see lots of different species happily feeding together.
For most wading birds, females have longer, slimmer bills than males, helping to reduce competition for food between them. This means that that the population as a whole can benefit from access to a wider range of food.
