All birds I heard this morning, before I saw them.
A couple of them I never even saw, but I am 100% certain they there because I heard them and I recognize their voices. I realized this morning that for the birds seen regularly in my neighborhood, I depend more on my hearing them than I do in seeing them.
Now, I'm not a master bird listener who has spent hours studying my Stokes CD's of bird songs. Having gone birding almost everyday for the last five years, I have simply grown accustomed to what the common birds sound like. I have also come to recognize when I hear something different, which really perks my interest.