I had some free time today :-)) Creative and scientific use of Melodyne Editor :-))
http://youtu.be/uSZIbfbSkBY

You conclude that the birds do not have perfect pitch.
 
What happens if you set "A₄" to equal 432Hz?

It was abit cold outside this morning so it may have influenced their throats :-))
I`m not an ornithologist but maybe birds can have a bad day also :-))
Mike , I will test out your suggestion :-))
All the best
Jan

yeah, I'm not sure that nature is tuned to 440. 

Hummingbirds are the punk rockers of the avian world.  They don't care about socialistic activities or pretty singing and, since I still have dozens upon dozens of them in my backyard, it can get pretty noisy with lots of fighting.  But they all seem happy.
 
I think a group of them should be called a Clash.  I believe I heard one say to get the flock out of here too.  Yep.  Punk rockers.

Hi,
 
I just put more food out there for the birds. As for music, I hardly think they give a damn about your theory and ideas! Just saying' ...

I don't know if they're in tune but they annoy the heck out of me. I'm not sure exactly what kind of birds they are but they seem to particularly love my neighbours pine trees. They have an amazingly diverse vocabulary and they're LOUD. 
 
When we moved here, I remember hearing one of them starting to sing at around 1 or 2 am every night. Took me a while to compute that this wasn't morning and that this fellow was indeed a few hours early or on a night schedule. After 40 years of birds singing at dawn, your brain makes certain assumptions...
 
Anyway, they're loud and loud and loud.
Give me bats over that anytime.

I have several Tuis in the garden and they sound like R2D2

You mean R2D2 sounds like several Tuis...
 
There is no such thing as "Perfect Pitch" in nature since its measurement was created by man for the soul purpose of establishing a standard for which to compare other notes to. From the lowest to the highest, there is no end in reality. Any note is a note by which other notes can be joined to create noise both harsh and melodic. As long as they are all in harmony then what does it matter what pitch they are.
 
I for one could never tell you what note you are playing. I can't read music, which is another form of measurement created by man so he can keep easier track of his compositions.
 
.
 

jps
I had some free time today :-)) Creative and scientific use of Melodyne Editor :-))
http://youtu.be/uSZIbfbSkBY

Very creative use of the tools!
 
I have to admit that after hearing the modified version, I felt more relaxed. Which now makes me wonder if the birds are doing this on purpose, just to mess with us?!?!
 
Thank you for sharing