Friday, April 12, 2013

A Tale of Two Grebes

On Wednesday I drove down to Thetford Forest to spend some time looking for Golden Pheasants. I had planned to spend the last few hours of daylight on Wednesday and the first couple of hours on Thursday hoping to get some photographs of this elusive and fast-disappearing species. On the way down I passed Fen Drayton RSPB reserve in Cambridgeshire and as I knew that there had been reports of both Black-necked and Slavonian Grebes I figured it was worth a diversion. I had a walk around Ferry Lagoon looking for migrants first of all but there was nothing bar four Chiffchaff and a lone Blackcap but at the southern end of the lagoon I managed to locate the Black-necked Grebe feeding a fair way out. However, it soon started to move nearer to the bank where I had set up my gear and pretty soon it was close enough to take photographs. I had been watching the bird through the camera lens and so had a narrow field of view. Taking my eye away from the lens so that I could have a quick look through my bins I was surprised to see two birds more-or-less together. The second was the Slavonian Grebe and this had appeared from nowhere. Both birds were in summer plumage; the Black-necked complete and the Slavonian almost so this was a great opportunity to compare these two scarce grebes side-by-side. I had never seen these together in summer plumage before. I have seen them together in the winter on a number of occasions.
Slavonian Grebe Podiceps auritus - Fen Drayton
The first thing that struck me was that the Black-necked Grebe looked slightly larger than the Slavonian but this could have been the result of it sitting higher in the water compounded by its steep forehead and peaked crown as both of these birds overlap in size - the Slav often being the larger. Both birds were sporting golden-yellow ear tufts - the tuft on the Slavonian was a little more ragged. Both birds had amazing red eyes. Note the bill in the photograph of the Slav below - straight, quite small and tipped pale yellowish/horn. The bill of a Black-necked Grebe is all black, up-tilted and sharply pointed. This bill difference is a good feature for separating the two species.
Slavonian Grebe Podiceps auritus - Fen Drayton
Because the Slavonian Grebe was not yet fully moulted it looked a bit untidy. If you compare these photographs you will see what I mean. There were still some winter plumage white feathers on the chin and upper throat as well as the upper breast but it was clear that the front and sides of the neck were turning reddish - a key difference between the two species as the neck of the Black-necked Grebe is all black - hence its name! The flanks too still had signs of winter plumage and were not yet entirely deep red.
Slavonian Grebe Podiceps auritus - Fen Drayton
The rear of the two birds was different with the Black-necked showing a fluffy, almost Little Grebe, back end whilst the Slavonian had a more stream-lined lower in the water end which was white.
You can see this feature in the picture below, although the Slav is out of focus due to a narrow depth of field. You can also tell the difference in head shape. The Black-necked has a steep forehead with the crown peaking directly over the eye, whereas the Slav's crown is flatter and has a definite peak behind the eye. The Slavonian has a longer sleeker body and looks a bit like a small Great Crested Grebe whereas the Black-necked recalls a big Little Grebe - if you know what I mean!
Black-necked Grebe and Slavonian Grebe Podiceps nigricollis and P. auritus - Fen Drayton
The Slavonian Grebe followed the Black-necked Grebe all of the time that I was watching. They behaved as if they were a pair with the Black-necked leading. Also the Black-necked called a number of times as it approached the bank but I don't think I heard the Slavonian Grebe at all. Both birds were happily feeding and appeared to be settled, they have both been present for some time.
Adult summer Black-necked Grebe Podiceps nigricollis - Fen Drayton
No doubt as the Slav progresses with its moult it will become more spectacular but it will have a way to go before it can beat the beauty of the Black-necked Grebe seen in the following two shots.
Adult summer Black-necked Grebe Podiceps nigricollis - Fen Drayton
In this portrait shot of Black-necked Grebe the tiny all-black up-tilted and sharp-pointed bill along with the incredibly steep forehead peaking above the eye are obvious. Both of these features tell you that you have a Black-necked Grebe and not a Slavonian.
Adult summer Black-necked Grebe Podiceps nigricollis -Fen Drayton


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