A rustling shadow in the planting... a flock of sparrows.
The spot is the azalea bed just in front after you leave the Palaceside Building onto Hakusan-dori =see photo left.
The photo above was taken at 7:40:21 a.m. on December 12, 2018. Walking from Otemachi Station that morning, crossing from the Marubeni side and about to enter at the Hitotsubashi door, the planting was noisy with chirps; I went closer and this is the instant sparrows popped their heads from among the leaves. Closer still they fled to the far side and took off one after another. A hundred or so?
We seem to have given them a start at wake-up.
This is not the only encounter. As evidence, the last two shots are February 2018 and February 2019, both after 5 p.m. Perhaps they were about to sleep here. I crept close so as not to disturb them.
I pass at almost the same time morning and evening, but I do not see them every day. They surely keep several "regular inns" and change spots. Seeing them more on winter mornings and evenings is likely the sunrise and sunset hours. Basically they wake with dawn and sleep at dusk.
Field guides say sparrow enemies are many: cats, shrikes, crows, raptors, snakes and other reptiles, weasels, spiders. So they do not casually sleep on power lines.
A report on the Ministry of the Environment Biodiversity Center site, "The 4th National Survey on the Natural Environment: Nationwide Distribution of Colonial Breeding Sites and Communal Roosts of Birds" (1994, http://www.biodic.go.jp/reports/4-03/e000.html), says:
Roosts were sometimes made on buildings and other artifacts, but most were in woodland such as mixed and bamboo groves (62%). They were also made in street trees and isolated trees, so large woods are not required; many were recorded in greens of 0.1 ha or less (57%). For a communal roost it is important that the trees have leaves; on deciduous trees the roost vanishes with leaf-fall or numbers drop sharply.
So this planting meets those conditions. It does feel a bit low, but the leaves cover densely and that must shelter them from enemies. Downtown, snakes and weasels among ground enemies are unlikely.
If you find a sparrow roost, please leave them be.
