That's a Red-rumped Swallow nest. Was this in Hong Kong? They are quite rare as breeding species here.
The sparrow was probably investigating potential nest sites. I think it's possible that it would take over a swallow nest if it thought it was suitable. Author: louislee Time: 6/06/2017 12:14
I saw in the photo description 嘉義 (Chiayi), which is a city in central Taiwan. Author: ssrg Time: 7/06/2017 01:24
In Hong Kong, both Tree Sparrow and Crested Myna will use House Swift nest.
And House swift will use Barn Swallow nest.
[ Last edited by ssrg at 7/06/2017 01:26 ]
Welcome to HKBWS Forum 香港觀鳥會討論區 (http://hkbws.org.hk/BBS/)