House Sparrow x Eurasian Tree Sparrow hybrid, Copenhagen (Denmark), 14th January 2015 - copyright Rasmus Strack
(photo ID: 2432)
This seems to be fairly typical of House x Tree Sparrow hybrids in having a limited wedge of grey extending back from the forecrown, a clear, if diffuse, dark cheek spot and buffy tones to the underparts. However we would like to see more photos in order to understand the range of variation in this hybrid.
These hybrids seem to be relatively frequent in Finland where the next one was photographed. Henry tells us it was quite a typical bird. Its shape was closer to Tree Sparrow and showed grey forecrown and cheek patch.
House Sparrow x Eurasian Tree Sparrow hybrid, Turku (Finland), 24th January 2010 - copyright Henry Lehto
(photo ID: 2559)
A bird purported by some to be House Sparrow x Eurasian Tree Sparrow appeared in Norfolk (UK) in 2013, though it was identified by others as a vagrant Italian Sparrow (and may also have been a House Sparrow x Spanish Sparrow hybrid). Details and photos of that bird appear here.
Another bird over-wintered in Norfolk, at Cley, in 2016/17 - this time a typical-looking House x Tree hybrid. It frequented feeders in Steve Gantlett's garden but also visited the feeders outside Cley Spy.
House Sparrow x Eurasian Tree Sparrow hybrid, Cley (Norfolk, UK), 18th January 2017 - copyright Dave Appleton
(photo IDs: 3146-3152)
House Sparrow Passer domesticus
Italian Sparrow Passer italiae
Spanish Sparrow Passer hispaniolensis
Eurasian Tree Sparrow Passer montanus