Robin

Hi, I couldn't say why he's singing 'to' you, but I've had the same thing happen, usually at this time of year, when the males are singing louder in order to attract a mate. I've had them singing very loudly and also a quieter sub-song, which is like a quiet warbling. It's quite enchanting isn't it? You can often get very close to them while they're singing. The fact that you're providing food probably helps.

Here's a clip of one of my male Robins from 2013. Similar situation.
http://youtu.be/jyPSn0kjeqk

Great to see that footage again MC, Robins are such wonderfully enchanting little birds!

As you probably know, both males and females sing. For robins, singing is overwhelmingly a territorial thing. The weather has warmed up since Saturday and they are now singing a lot here....esp compared to last week when it was far colder.

Many birds do sing to attract mates, esp migrants like nightingales and warblers that often arrive alone and in habitats where they're well hidden. Robins, however, often already have mates and territories by now. They're also more widespread and common, and often more visible, so finding a mate doesn't need weeks of singing in most cases.

Robins also spend much of dawn and dusk, incl darkness hours, singing. Your presence and your food was timed at a time when the robin was probably going to be singing anyway, to state it's there, in its territory, and to ward off any rivals.