Bird2 and protocol Babel. auto change default gw

Hi, I am new to ML and also to using bird2. I use bird2 with babel protocol for routing the vpn server and openwrt router. The openwrt routers have a mesh wifi interface. My question is, if the wan (default gw) is down, can bird use the better mesh as the default gw? If the wan is restored, can it come back as default gw? Best regards, Michele