Because GrandDaughter is still in a lying-back position in her pushchair, my running commentary on the 'ickle lambs and the woolly pony, the snowdrops and the silly car driver who should have slowed down is largely irrelevant to her.
So I focused on something she could see: the sky. A few little clouds wandered into her line of vision so we played 'See what you can see in the clouds'. I got quite excited as I could see an elephant. GrandDaughter looked skeptical until I explained that it was all because of perspective that his head looked so much bigger than his body.
I think she found it easier when we saw real catkins and I explained about spring and baby birds (who go tweet) and baby lambs (who go baa). I was about to tell her about a young man's fancy but thought better of it.