Before that I took a quick trip round the park to see the essential Little Owl at the leaf yard, rather hard to see amid the leaves.
The two young Carrion Crows from the nest near the Henry Moore sculpture were out and pestering their parents.
In the middle of a large group of Wood Pigeons feeding on the ground there was a solitary Stock Dove.
Although there were plenty of Reed Warblers at Rainham, the only one I could get a photograph of was in Hyde Park, at the east end of the Serpentine.
But there were lots of interesting creatures to see at Rainham, such as this Marsh Harrier, one of two that were circling in the distance.
A Redshank posed obligingly on a gatepost.
There were several Lapwings ...
... and a Shelduck on the scrape.
This Oystercatcher was on the Thames mudflats.
Unusually, most of the interesting sightings were of land birds, such as a young Linnet.
There was a Reed Bunting just outside the reserve near the riverside walk ...
... an a distant view of a female Stonechat.
... a cock Pheasant skulked in the long grass.
A Wheatear crossed the boardwalk.
A little farther along the boardwalk was a Painted Lady butterfly.
To a central Londoner House Sparrows are exotic. This young one was among two dozen in the bushes near the Visitor Centre.
The strangest sight of the day was a Marsh Frog making a tremendous noise by inflating and emptying his pouches. He was competing with a rival a few yards away. I made a video of this.
At the end, you can hear one of the numerous Cetti's Warblers singing.