Good evening, Elle!
It seems that large broods help to ensure that some young birds will survive.
That will be the strategy.
4d, I was surprised with this one, Elle, as I thought the answer was two words?
But, anyway, "leftfield".
In many field games a red card shown to a player means he has offended and must take no further part in the game, and he has "left field".
I think the "leftfield" is an American term for "unusual".
12a, Think Maureen O'Hara! She was "Herself"
This answer is "Himself".
A word much used in Ireland.
The great racehorse, Arkle, used to get fanmail addressed to "Himself, Ireland"!
I think our setter is indicating that if he was not feeling himself that day, he was not in good form.
What do you think?
28, Stop is "kick", a habit, say. "stick" means "stand", as in "I can not stick/stand that TV show.
And kickstands are used on some bikes.
How's that?