Sunday, 24 February 2013

Territorial Great Crested Grebes

ResearchBlogging.orgThe breeding season of the Great Crested Grebes is approaching. I have never seen their spectacular courtship so I thought I would pay them a visit in a local park where they breed regularly. I had almost given up on finding them when, from the bridge, I located a winter plumage individual at the far end of the lake. When I got there, I saw that there were two winter plumage individuals, and then an individual with full breeding plumage emerged from the water quite close to me (above). Breeding plumage individuals have a long dark crest and orange and black 'tippets' on the sides on the head, while these are lacking in the winter plumage. I sat down and watched the interactions between the breeding plumage and one of the winter plumage ones. The breeding plumage individual watched the other one, and approached slowly, nonchalantly, occasionally preening its back, or shaking its head, but the winter plumage one appeared to take offence, and swam in the aggressive posture of this species, with head low and stretched forward over the water, and then started to fly, while paddling on the water, towards the breeding plumage one and kept it away. Occasionally it would try to approach diving (see video below). This behaviour went on for quite a while. Both winter plumage individuals appreared tolerant to each other and at some point they stayed close together, so I wonder if I they were displaying early territorial behaviour, and the breeding plumage individual was trying to find a new mate.
 Great Crested Grebes show some variability in their head moult and in February a range of plumages from full winter to full breeding can be seen, so the three individuals were likely adults in different stages of their moult.
Changes in the plumage of the head. The plumage types of individual grebes in relation to date are
given (males = filled and females = open symbols). Dots refer to scores based on examining photographs of grebe-heads, whereas the triangles indicate the results of examining museum-skins. (from Piersma, 1988)

Winter plumage individual on agressive posture,  a few crest feathers and the dark tips of the tippets have already emerged.
 Breeding plumage individual preening its back feathers
It appeared to try and grab the attention from the winter plumage individual, and... very close. 
But it got the wrong sort of attention, as the winter plumage individual threatened it
the summer plumage individual flies away. 
The two winter plumaged individuals close to each other, watched by the breeding plumage one

A couple of short videos on the interactions between the two individuals.

More information
Theunis Piersma (1988). The annual molt cycle of Great Crested Grebes. Ardea, 76, 82-95

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