from >2% to <1%, only thing I have changed recently is adding google search box in header. Or is it the trend in travel sites?
How long has it been like that? Don't press the panic button yet because as you've said, there's no changes other than adding a search bar and definitely adding a search bar is not going to affect anything.
Give it some more time, it does not seem logical that adding a search box might deter ur visitors from clicking the ads....