Swallows and White Wagtails roosting

At dusk yesterday, saw around flock of around 70 Barn Swallows swirling around over waterfront buildings, before going to roost. Seems typical that after breeding, swallows here gather in groups like this:  may perch together on tv aerials, or on wires over buildings.
Pretty soon, though, they'll "disappear" - going south for the winter.

White Wagtails also roost in the evenings - in trees just north of the ferry pier. I've seen up to around 50 roosting here; maybe more than can find in daytime on Cheung Chau, so some maybe from over on Lantau. As this species is chiefly a migrant and winter visitor in Hong Kong, with rather few breeding, roosting numbers should be highest in winter - though I haven't checked this.
Also of a little note: three days ago, saw pair of Blue Magpies with at least two fledglings near the Sports Ground. My first confirmation of breeding on Cheung Chau; when I first came, these magpies weren't present, but seems they've moved in as tree cover has matured.
And on Sunday, around dusk, surely head Common Sandpiper at Kwun Yam Wan: if so, my first autumn migrant.