Tim writes: I managed to capture the moment that this Slavonian Grebe opened its bill. It didn’t seem to be for any particular reason as it didn’t make a sound. I presumed that she was incubating eggs but her partner approached calling and she lowered he head inviting him to mate, and he did just that, while remaining on the nest. This seems odd because grebes can only lay one egg a day at most. But they don’t start incubating until the full clutch of 4 or 5 eggs is laid. This means that all the young hatch simultaneously so they can be taken around as a group by the parents. Grebes cover their white eggs with weed as a disguise when they leave the nest or until the full clutch is ready to incubate. But this female sat tight, making me think she was incubating. So why was she mating if the full clutch was laid? Maybe she just felt like it. This was at a village pond in Swedish Lapland with lots of people around. The grebes seemed oblivious to all the people.
The name Slavonian appears to be a misnomer. It is a very old name first used in 1802 by Lt Col George Montagu in his Ornithological Dictionary, which was the first proper list of British birds. His entry here said “Horned or Sclavonian (sic) Grebe” with the remark that Dr John Latham says that it is found in Sclavonia, a reference to an area in northern Russia. However, the 19th century Kingdom of Slavonia was not in northern Russia, but was south of Hungary which is way outside the breeding range. Maybe Latham was confused as he was principally known for describing bird specimens that others brought back to England, rather than going on expeditions himself.