@ what speed would I need to fly heading west to be able to keep looking @ a sunset.....(what speed is the night time shadow across the earth)

I don't see the benefit of sleeping at night in the wild, especially since this is when the animal is most vulnerable... 

During a lecture on vertebrate reproduction, we were told by our lecturer, that no animal can stop birth. Is this correct? I have been told once before that in the wild Zebras can stop themselves having contractions during the day so they are not suseptable to predation and will only give birth during the night. Is this true? Are there any other mammals that can do this?

Recently I've been up late at night and have noticed something rather strange about the birds in my area: they will continuously sing from about 11pm until 3am, possibly even later. At this time of year (middle of January), it won't be fully bright until about 7 or 8, getting dark at 5 or 6 in the evening. What is their reason for doing this? I live relatively close to the centre of Dublin. Is light pollution an issue?

Stephen,

Dublin, Ireland

On the first night of heavy snow - tues 5th Jan - it was cloudy but the sky was  a very light sepia tone all night - enough to see clearly by. It was much more light than on the subsequent nights which have been partially cloudy with a visible moon. On these nights there was the same amount of snow cover, but less cloud. 

On the sepia night it was lighter than if there had been a full moon.