one of my highs would be a male osprey returning for the second year to build an eyrie visible from my attic window!
Low would be a complete lack of wrens from the straths and uplands after the hard winter weather!
Highs were probably finding and photographing a Black-banded Owl in the Pantanal and the Atlantic Rainforest race of Long-tailed Potoo (surely to be split from Amazonian populations).
Lows... not sure, maybe missing the photo of a Swainson's Thrush here in the Atlantic Rainforest