New sibling

I guess the balance has shifted & baby gets lots of your attention (as any baby needs)...but all that means to littledub is that he is not getting your attention. (....or any attention he is getting is due to his tantrums both at home and at daycare, which to a little person is better than nothing).
At 2 and a half he won't understand that you have your hands full...He'll still be self focused (which is age appropriate) and only has the capacity to feel what he is missing out on...and so, see the little new baby as the thing that's changed his world. It's ok....it's just a change.

If it were me, I would probably....
1)Initially carry on ignoring the tantrums, where you can...
2)Increase (if humanly possible) the positive attention your toddler is getting - so, if you can snatch a moment here and there to have some stories or one on one time with LittleDub; special time with your partner/grandma/nana friends; watch out for snippets of good behaviour and praise praise praise positive positive positive; involve him in your tasks with baby (so baby is getting needs met but toddler is also getting attention)....Once you have increased positive interactions and are (hopefully) both feeling a bit more positive about things in general I would then go on to...
3)tackle any ongoing difficult behaviour...perhaps chose one thing at a time to focus on. For example if say pushing is still a problem, maybe having a way of using time out (eg a minimal attention response) to respond to that.

What people often find is that increasing the positive attention to positive behaviours before tackling the negative behaviour can sometime shift the balance enough that the bad/tantrum behaviour actually reduces to a more manageable level on its own.

Hopefully that makes a bit of sense?

GOOD LUCK!!!

Thank you Sally and Kellz

Oh god my DS was exactly the same! The only thing that consistently worked for him was lots of positive attention which is so blimmin hard with a new baby. That, and lots of time out in his cot

My #2 bub is still a couple of months off arriving, so I don't have any advice from experience, but what I'm planning on doing is spending heaps of time at the park, library and other places DS (age 2yrs 9 months) loves, where I can sit and breastfeed and he can play with other kids and burn off his energy. Investing in active outdoor toys for outside at home is worth it too - sandpit, slide, ride-on toys etc.

I find the more exercise he gets, the easier he is to deal with. If we have to stay at home for days because of bad weather, he is a total maniac... aggressive, destructive. But a couple of hours at the park sorts him out. I also get DP to take him swimming and for long bush walks.