Great Crested Grebe
This handsome bird is a familiar enough sight on many of our waterbodies, most often associated with large and shallow lakes during the breeding season but with birds also using our coastal waters during winter.
The Great Crested Grebe is something of a conservation success story. Up until about 1850 the species was distributed across much of central and eastern England but the latter half of the 19th Century saw the breeding population reduced to as few as 32 pairs. The reason for this dramatic change in fortunes was the Great Exhibition, at which the furriers Robert Clarke & Sons exhibited the pelts of four birds in full breeding plumage. This led to the development of a trade in which the pelts were used as a substitute for animal furs in boas and muffs; the feathers were also used in the millinery trade. Successful campaigns against these trades led to a succession of bird protection acts that ultimately saw the population recover. While a grebe in full breeding plumage is fairly easy to identify, identification of birds in their winter plumage can be more difficult. The BTO video guide to winter-plumage grebes provides some helpful tips.
Taking to the wing
Adapted for an aquatic lifestyle, Great Crested Grebes struggle to get airborne and require a long run-up, something that sees them avoid our smaller lakes and ponds. Yet, when on the water, they are graceful-looking birds, whose ornate plumage and stunning courtship displays make them a firm favourite with birdwatchers. Great Crested Grebes are capable of substantial migratory movements, which see individuals from elsewhere in Europe arrive to winter around our shores.
The movements of British and Irish breeders are poorly known because of the difficulties in catching the birds for ringing but the evidence available suggests dispersal from inland water bodies during late summer, with the birds moving to wintering sites on which their annual moult will also take place. More widely, researchers have noted changes in the wintering distribution of Great Crested Grebes within Europe since the 1970s. Some of the largest concentrations of wintering grebes are found in the Netherlands and the southern Baltic. On the Ijsselmeer (Netherlands) peak numbers in excess of 40,000 individuals have been noted. Within Britain and Ireland, the peak counts revealed by the online WeBS report fall far short of such highs: Dungeness and Rye Bay averages a peak of c.2,000 birds, while Loughs Neagh and Beg average c.750.
A stunning display
Much of the Great Crested Grebe’s courtship display is centred on strengthening the pair bond, and a number of distinct behaviours are recognised. The head-shaking display is probably the most familiar; in this, the head plumage is fanned into a ruff before the birds then face each other and shake their heads from side to side. The display is seen predominantly during the early stages of courtship and is usually performed when the pair is reunited after a period of separation, suggesting that it is used as a greeting and for reinforcement.
The most elaborate of the great-crested grebe’s displays is the ‘weed ceremony’ which, as its name suggests, takes place just before the pair begin to build their nest platform. As part of this ceremony the two birds make a slow and deliberate dive to collect weed, before returning to the water’s surface and swimming towards each other, their heads held low to the surface. As they meet, the birds rise from the horizontal to adopt a rigid vertical posture, which they hold by paddling their webbed feet rapidly, treading the water.
A cautious parent
Although the courtship displays announce the presence of the breeding grebes, the birds become more retiring once the first egg has been laid. When incubating, the sitting bird (both members of the pair do their share) will slip off the nest if it spots a distant predator. If a bird has more time when leaving the nest then it will cover the eggs with waterweed, which is why the eggs quickly change colour from white to a muddy brown. This reduces the chances of the eggs being spotted by a predator. The resulting chicks would also be at risk were they to spend long in the nest, which is why they leave with their parents within a few hours of hatching. At this young age the parents often carry the small chicks on their back, which can make them surprisingly difficult to spot.
Working together for seabirds
BTO work supports effective monitoring of our seabirds and aims to provide opportunities for a new generation of seabird surveyors.
Counting birds and the Wetland Bird Survey (Wednesday 22 September, 10am)
This course involves one online session of about 1 hour 45 minutes, with a trainer:participant ratio of about 1:30. Participants' microphones are muted during the presentations but there is a large interactive component...