Maybe cos that's it's immediate surroundings and territory ??

I was on Stalybridge Station, near Platform 3, yesterday morning (Sat 24th April) about 6.20am. In a tree, there was a blackbird singing away. I suddenly realised that it was making the same noise as some trucks make when they reverse. There is a large works just behind, with some Viridor trucks. So, I wonder if the blackbird has heard the noise and imitates it for some reason. It is a series of about 7 or 8 notes, repeated several times. Any idea why it would do that? Peter