Today, I used the app on my Android phone to scan one of the Gibraltar stamp images. I did not hear any sound, but there was an option to link to somewhere to order the stamp. For Gibraltar, the correct page came up in my browser, but details of the issue were not yet available.
More interestingly, there is a link to "More Bird Stamps" which was a great surprise, as in addition to those we already knew about, there are several stamps illustrated of which I was not yet aware, including a new species on stamps: Greece has Western Rock Nuthatch (Sitta neumayer).
NB. PostEurop clarified its definition of "National Birds" to be "National birds are native birds living on the territory of a country", which gives much more scope than most of us initially thought.