Shallow divers

The two regular diving duck species on the estuary at this time are Red-breasted Merganser and Goldeneye. The local guide books always mention them, but sometimes visitors leave disappointed. They are not easy. There are never that many of them, and it's a big estuary.

As with any visit, you need to be thinking about the state of the tide.

Both species feed routinely at just a few metres' depth, and follow their prey. High tides can be frustrating. Making/falling tides can be the best bet.

This morning was one of the good days. Arriving at Bloors Wharf just as the water started to ebb from the shore, a pair of drake Mergansers had taken a liking to Rainham Creek. Creeks are often a lure for the fresh water, but they were more interested in feeding. The Creek had been excellent the day before when a Common Seal was clearly catching Flounders with ease, and today must have had small shoals present as the Mergs continued to feed actively for the 90 minutes I watched them.

There was also a pair of Drake Goldeneye, but much further out, on the northern edge of Bartlett Creek. "Adequate 'scope views" in the birding parlance. (That is, if you squint you can just , just, make out the cheek patch. With imagination.)

I returned at low tide in the late afternoon. A mile of mud, but knowing where to squint found the birds settled in the shallow creek separating Nor Marsh and Friar's Saltings. The creek holds a fair depth of water (and food) over a neap low water.

The Mergs continued to feed, but now the Goldeneye were displaying. There were now four, three males and a female. Two males kept tight to the wake of the female, displaying at her all the time. Courtship display.

Intriguingly, among ducks there is a fine line between love and hate. The same movements that make up the courtship display can often be found in territorial defence and in outright aggression.

So what exactly was in the mind of the third Goldeneye was a little harder to tell. He sat just a matter of metres away, busy going through the very same motions, all the head-pointing, the head upending, the bowspriting that the other males were engaged in, but he was displaying at a Great Crested Grebe.

Had the Grebe been fishing too close? Was this pent-up frustration being vented, with the female preferring the other males? Impossible to tell which side of the fine line, but the Grebe remained completely indifferent either way.