What are waders, or shorebirds?
The 213 species worldwide have found niches almost everywhere. From the plateaus of the Andes and the Rift Valley lakes to the estuaries and the tundra of the north, waders can be found on all but one of the Earth's continents. Spend long enough on any coastline and you will eventually find shorebird, and if you are in the right place at the right time, perhaps witness the spectacle of hundreds of thousands of waders flying as one in a swirling cloud of wings. The Banc D'Arguin in Mauritania is such a place. Every winter, up to 2 milion waders call home to this magical wetland, bordered by the mighty Sahara desert. Such places are of incredible importance for these global travellers.
Some waders rank among the World's greatest travellers. The Red Knot, a bird only weighing 100-200g, visits South Africa and the tip of South America for the southern summer before flying to the Arctic tundra to breed in the northern summer. The bird on the left, ringed on its nest in the Canadian Arctic has since been to winter in South America and is now feeding in the USA on its way back to the Arctic. More impressive still, the Bar-tailed Godwit flies non-stop for 9 days to cross the Pacific from Alaska to New Zealand. During this amazing trip each bird displays physical performance and endurance that would put the best cyclists of the Tour de France to shame.
Waders come in a variety of sizes. The American Curlew can weigh up to 1 Kg and stand as tall as a Spaniel. Its impressive 20 cm long crescent shaped bill is actually longer then a Little Stint, one of the smallest shorebirds in the World. This tinny birds weigh only half the mass of a golf ball, but that doesn't stop them from migrating every year from the Arctic to the southernmost reaches of Africa. Before this long migration they need to accumulate fat reserves, eventually becoming as heavy as that golf ball just before departure.
Eating is a serious business in the wader world. Some species are highly specialized shellfish hunters, and the Red Knot even has a unique “sixth sense” which allows it to find clams buried under the mud. Snails, crabs and worms are also frequently on the menu of estuarine shorebirds. Many species prefer to eat inland, where earthworms and insects become the gourmet food for waders. Some species can even eat plant material, like some Black-tailed Godwits that eat rice grain for most of the year.
Waders, like all other birds, are oviparous in that they lay a clutch of eggs as the means of reproducing. Their nests are generally on the ground and need to be kept safe from predators as well as warm for the eggs to hatch. The question here is who takes care of those eggs? Many species are monogamous and form stable pairs that can last many years, with both mother and father sharing the burden of rearing the young. In some cases, like the Lapwing, one male can take care of two or three nests, with two or three females who will do most of the work. One extreme case of polygamy is the Ruff, where the dominant males will copulate with many different females and leave the breeding area even before the eggs are layed, leaving the females to do all the work. However, its not always the females who get the extra work in the wader world. The Jacanas and the Phalaropes are polyandrous, which means each female has several males. A good example is the female Red Phalarope, which is bigger and more colourful than the male and often engages in fights with other females. It has no role whatsoever in incubating the eggs and taking care of the young. The female will spend some days with a male, courting it and laying eggs in its nest. Once the nest is full the female begins searching for another male. Before the eggs have hatched the female has already headed south in migration.
The waders form a fascinating bird group, which as captured the imagination of many bird enthusiasts from around the World, many of whom are members of the International Wader Study Group. Join us and find out more about waders and help us support wader science and conservation worldwide.