If birding is one of the activities planned on the trip, I take my regular birding binoculars. In the past, those were my 10X42 Leica BAs, now they're my 8X32 Leica BAs. The first time I went to Europe (first time outside North America), I brought along my 80 mm scope too. Birding wasn't the principal goal of that trip, but I knew I would have at least a few days where I could bird seriously and wanted the scope to see a lot of birds I knew would be new for me.
As I've grown older, I'm less likely to schlepp a scope around--and the 8X32s really work just fine for most birding--serious or casual. Just this week, however, I ordered a pair of 8X20 Ultravid compacts--mostly because I was leaving my 8X32s at home or in the hotel when I was traveling in cities--and also leaving them (not easily accessible) in my backpack while hiking because their weight bothers my back after hours of walking. I'm hoping the 8X20s become the binoculars I take with me when I'm not really birding, but just want to be prepared in case something interesting flies by.
I may someday again get a binocular with a 42 mm or even 50 mm objective for more serious birding (including when traveling), but those 8X32s are hard to beat in most situations and a nice size and weight for any travel except (in my opinion) travel where birding would only be an incidental activity--you, know, you're having a glass of wine with your non-birding friends at a cafe in Paris and all of a sudden your life Eurasian Hobby flies over . . that's the travel niche I'm hoping the 8X20s fill.
