Webcam

Actually you will need two cameras, as filming someone coming to the front door from an upstairs window is pants.

My personal favourite is to have a hidden camera in a clock in the downstairs front window nearest the front door. Everyone looks to see what time it is and then you've got a full face picture.
Something like this: www.habitek.co.uk/Habitek...m00384.htm
But if you're willing and have a bit of DIY you could make something much better quite easily.

For the birds something like this: www.vista-cctv.com/web/pr...-vpcm.html
You need high resolution, and a good frame rate as birds flap their wings surprisingly fast, so generally the lower the lux the quicker it can take a picky in normal light, the quicker the picky the more sharp it will be on a moving image.

Can anyone recommend a webcam that can be used for security. It will be placed behind an upstairs window and I would like it to capture people arriving at the front of my house in as wide a variety of light conditions as possible, with good quality output.

As a secondary use I would like to be able to capture birds entering a nest box about 10 feet from the camera that will be viewing from behind glass.

I reckon the primary requirement is no problem as wide angle viewing is what these things are designed for - the nestbox thing could be a bit more tricky?