Strange nightime noises

I couldn't resist another nocturnal outing yesterday this time choosing Nittedal as the main destination. In the end it was too cold and there was too much traffic noise such that I only heard some distant noises that I was unable to identify. At Hellerudsletta though I did hear a warbler singing and was able to get close to it in the dark. It was singing slowly and I was really unsure as to its identity for a long time. There were some extended periods of song when I was convinced I was listening to a Blyth's Reed (busksanger) but it failed to utter any of the characteristic notes of Blyth's and it did have short periods when it just sounded like a Marsh. On xeno-canto there are recordings which have been labelled as possible hybrid between the two species and this bird resembles them but there is so much variation within Marsh Warbler (myrsanger) that I’ve concluded it was just a laid back Marsh.

On the way home I had to try Maridalen although the Fieldfares (gråtrost) started making a din already at 01:45 which made it hard work. Two Marsh Warblers eventually announced their presence, Tawny Owls (kattugle) were calling at a new location and the Grasshopper Warbler (gresshoppesanger) was reeling away close to the lake and therefore much harder to hear than normally.
A Fieldfare (with a cold) had me going for a bit as it was making a noise very similar to a begging young Long-eared Owl (hornugle) but I eventually saw the bird. A Whinchat (buskskvett) started singing just after 2am and did an excellent mimic of both Common Rosefinch (rosenfink) and Yellowhammer (gulspurv) - I would have loved to have heard the Whinchat that apparently mimicked River Warbler (elvesanger) so well that birders were ticking it (I think it took a while before people realised it was a bit odd that it always sang (invisibly) from the same bush that a Whinchat was sitting in!).

Today I walked up to Dausjøen but failed to see the Whooper Swan (sangsvane) family although they could well have been in an area not visible to me. An Osprey (fiskeørn) was searching for food over the lake before eventually circling to such a height that it was just a black dot in the binoculars before drifting off north east. I disturbed one of the Wrynecks (vendehals) whilst it was feeding on the ground but didn’t succeed in locating a Marsh Warbler which I had hoped to be able to photograph.