What's wrong with this picture? OK, it's not the finest shot of a female Red-backed Fairy-Wren (Malurus melanocephalus), but that's not the real question.
Seconds before, a pale and very juvenile Horsfield's Bronze-Cuckoo (Chrysococcyx basalis) was sitting on the branches when the wren flew in. The cuckoos parasitise the wrens, so I expected some passing of food.
But the cuckoo didn't even acknowledge the wren's arrival. It fluttered off a bit shakily into higher cover. (The heavily overcast day and the cuckoo's extreme lack of colour together proved too much for autofocus: too late, I tried going to manual.) No sight or sound of any other wrens, or adult cuckoos.
So, just me and the wren, which flew down as if into a nest in the long grass. Perfectly normal. Except there was no nest. Carefully and thoroughly I checked the area. Nothing!
It's not so much that I'd jumped to conclusions, rather that even the most rational lines of thought can unravel when put to the test by nature's complex threads.