Dance of the grebes
Played out on lakes and rivers, the elaborate courtship ceremony of the great crested grebe is one of nature’s most spectacular
The late winter sun begins to rise in the sky, casting long shadows from the alder trees along the bank of a quiet lake. On the glassy surface, two slender birds are swimming around, seemingly taking no interest in each other. They occasionally dive beneath the water to feed. But there is more going on than might initially appear. This pair of great crested grebes are about to embark on one of the most important aspects of their lives: their courtship display. It is the first stage in the long process of breeding and raising a family. For most of the grebes this is a new pairing, although occasionally a bond may last throughout the winter. In autumn and early winter, great crested grebes are plain-looking birds, with a long white neck, narrow head, sharp, pointed bill and buff-coloured back and wings. But from January onwards, once they have moulted into their breeding finery, male and female turn into very handsome birds. Both sexes gain the feature from which their name comes. This is a distinctive, chestnut-brown crest protruding from the top and back of their crown, together with a ruff of feathers that runs around the face. Raised to attract a mate, the crest is a crucial feature in the courtship display, which takes place from early in the new year through to late February or March and, in some years, later into the spring. Their elaborate performance can be seen on lakes, rivers and gravel pits across much of the southern half of Britain.
Early morning show
Now, as the sun spreads its rays across the water, the ceremony begins. First, the male bird swims closer to his mate, approaching her from the front so that she cannot ignore him any longer. Even so, she may turn and swim away from him, as if testing his commitment to their relationship. In fact, that is exactly what she is doing, in her own quiet and subtle way. Undaunted, he persists. On this occasion, she takes more notice and turns to face him for the first time. Initially, they do not seem to do very much. There is a
rapid shake of the head, followed by a quick preen of the wing feathers with that pointed bill. For the next few minutes, the two grebes edgily circle one another, frequently pausing to preen. Then the action proper gets going. The birds face one another and begin an elaborate series of head movements, each precisely following the other as if they are looking at themselves in the mirror. To an observer this can appear odd, but it is crucial in cementing the pair bond between male and female. They are going to spend the next two or three months raising a family together, so trust and mutual understanding is vital. Either or both birds will take the lead in this mirroring. Sometimes, indeed on most occasions, the display ends there. Having gone through the ritualistic motions and reinforced the connection between them, the birds part once more and resume feeding. On occasion, however, they follow through to the climax of the show, a bizarre and memorable ritual known as the penguin or weed dance. This is a fascinating display, which appears to have no practical purpose. At first, they move apart, and it seems as if courtship is over. Then each bird dives in synchrony, reappearing carrying a beakful of waterweed. Both rise up from the water, their legs beating frantically to keep them vertical, and wave the weed at one another.
A life on the water
Grebes live nearly all their lives on the water. Ducks, geese, swans, coots and moorhens are often seen feeding or roosting on land, and even seabirds come ashore to breed. Grebes, however, never leave the water, apart from to fly. They make their floating nest on its surface rather than on the adjacent land. If they did try to walk, they would struggle, as their legs are placed very far back on their body, almost underneath the tail. This is perfect for propelling them through the water when swimming or diving, but not good for walking even short distances. The legs are flattened and the toes have broad, leaf-like lobes. This means the forward stroke underwater has minimum drag, but the backward stroke can exert maximum pressure for forward movement. Measuring 19in (48cm) long and weighing between 30-38oz (900-1100g) great crested grebes have a superficial resemblance to ducks. However, the two groups are completely unrelated. Their similarities are entirely the result of convergent evolution, as each group has evolved adaptations to suit its habitat. Great crested grebes have fairly short wings, measuring approximately 25in (70cm) long. They are able to fly reasonable distances; for example, out to sea in winter, but do not perform long migrations. Take-off requires running along the surface of the water and flapping their wings to get airborne. They usually feed near the surface, although they can dive to depths of several feet. Here, they are adept at pursuing fish underwater, before seizing them with a
pincer-like bill. Other prey include a range of aquatic creatures, such as crustaceans, molluscs and amphibians. There are approximately 4,600 breeding pairs in the UK, with a bias towards the south and east. The species does nest in Wales and Northern Ireland, but there are only a few pairs in southern Scotland. In autumn and winter, some head away from inland waterways to the coast, feeding on estuaries or just offshore.
Family home
During the breeding season, however, great created grebes can be found on a wide range of small and large waterbodies. Following the courtship ritual, the now closely-bonded pair will build a floating nest out of aquatic vegetation, usually anchored to the bottom of the lake or a protruding branch. The site will be on the edge of the water, where it is shallow. When the nest is complete, the female lays three or four long, white, ovoid eggs, one each day. Once the final egg has been produced, both male and female will start to incubate them. During this period, each will occasionally leave the nest to find food. To protect their precious clutch, the eggs are covered with waterweed. As time goes on, they turn a shade of dirty green, rather than their original white. The eggs hatch after approximately four weeks. The baby grebes are precocial, meaning they are able to leave the nest, swim and find food almost immediately after hatching. At this early stage in their lives, the young birds look nothing like their parents. Their plumage is striped black and white, like an old-fashioned humbug. Although they can swim and even dive to find food for themselves, they often hitch a ride on one of their parents’ backs. Here, they are relatively safe from any predators, such as otters or pike. For the next 10 weeks, the youngsters remain in the care of the adults, which still feed them from time to time. They also occasionally feed the youngsters small feathers, which help aid their digestion. Gradually, the chicks start to lose the distinctive stripy plumage and moult into their adult feathers. Once this happens, they become independent. With a life expectancy of nine years, they do not start breeding until they are two years old. Unless the adult grebes decide to have a second brood, a comparatively rare occurrence, their work is now over for another year. By early autumn, they have moulted back into their less showy non-breeding garb. It will be several months before they will dress for a new courtship dance.