Does anyone know when this officer joined the 10th Austrian Hussars? He became it's commander in mid -1809 and led it until 1812, however he was promoted to Lieutenant-Colonel in 1808. He had been with the 1st Uhlans from 1806. Previously he had spells with the Kiermayr Hussars 1800-1804 and the Kavanagh (Cavanagh, Kavanaugh?) Kurassiers 1794-1800, as well as a short period on the army staff 1805-06.
https://www.napoleon-series.org/military-info/organization/Austria/cavalry/c_austriancav2.html#1
https://de.wikisource.org/wiki/BLK%C3%96:Starhemberg,_Anton_Gundakar_Graf
He led the Radetzky Hussars in the 1813 campaign before being made GM(October 1813?)
Hirtenfeld suggests somewhere between Austerlitz and Aspern http://digital.ub.uni-duesseldorf.de/ihd/content/pageview/9381357?query=Starhemberg.
He was an Oberlt and then Rittmeister in 1799 with 8. Kienmayer Husaren. He left the army at the end of 1804 as a Major. However he soon returned as a Major and Flugel-Adjutant on the staff of GM Kienmayer. He was appointed as Oberst-lt in 1. Uhlanen soon after Austerlitz.
The history of 10. Husaren says a Rittmeister Graf Starhemberg was transferred from 10. To 2. Husaren on 1stNovember 1807. https://books.googleusercontent.com/books/content?req=AKW5Qad7ShZwQXedMWLbNkgnfJsfak0n830M4TupANjc-0mnyJcyQagulrOf1DJ89sJxjnG_4Gpcif4JHXw8vUIXe-BSrFnGLgSqJum6nI97bHLfI4PuQbLtmiiWl6TY7Xu2YNWkQwO36DIjKzTDxWFj6mb5wbfpvQnGRgpRtizO-n2hWLD0I5MKpolt-H39mKPorrqN2mpuKmBMYbxrt9qxw9r9abgevwyH3h5nWxJHOdg_EPTN9WCde7Venl1LlqmBUpnTRkTdy-6rw3tKpw6ab7c043apThpBMv3j5qRHvJz4h_WYiuc p.236
However, it does not look like him as Rittmeister is a captain and on 27th May 1809, Gundakar was transferred from Oberstleutnant of 1. Merveldt Uhlanen to 10. Husaren as its commanding Oberst.(p.257)