Jumping in a song

Hi, been using the site for around a month now and am a beginner.

I want to learn to sing Sailing by Rod Stewart as I like to play this on my guitar https://tabs.ultimate-guitar.com/tab/rod-stewart/sailing-chords-380559

The first line jumps from C to Am and I think it's quite a big jump from a low voice to a high one. At least it seems it to me. It sounds a bit weird to go from what is probably chest voice to maybe mixed or head voice (just guessing here!). Does anybody have any tips as to how to make this transition smooth?

Thanks,
Moles

It is a big jump - up to an Ab/G#. That's definitely in mix territory for a tenor voice (as Rod Stewart is). I'd recommend checking out the following lesson + article to help with a transition like this:

Mixed voice: https://www.youtube.com/watch?v=0soCFM4YSIE&t=699s

Shifting registers: https://www.30daysinger.com/blog/shifting-between-vocal-registers-how-to-transition-smoothly-avoid-cracking