This Cocoa (formerly Buff-throated) Woodcreeper (Xiphorhynchus sussurans (formerly lumped in with X. guttatus)) was our alarm clock at Manuel Antonio (Costa Rica) - he sings the first parts over and over and over every 6 seconds for 30+ minutes in the morning, occasionally including the "churrs". Woodcreepers are some of those notoriously difficult to identify by sight birds, but each has it's unique song.