Out on our nature strip, right beside the road, a pair of Eastern Rosellas have opted to nest in the hollow of a trunk about 2metres above the ground. The opening is particularly small and the birds have to squeeze through with considerable effort each time they enter or exit the nest.
After this bird flew off this morning,
I placed my lens cover across the opening for comparison.
The widest part of the opening behind is about 3/4 the diameter of the cover, or around 30 to 40mm. Marvelous.