Sealant Damage External Window

[andygray]

Does anyone know the best way of filling this gap of sealant that has eroded/ or eaten by birds? There is expanding foam behind. See photo. Gap is 1-1.5 inch

There are so many fillers/sealants out there now. Obviously a robust solution is required. If it has to mean some sort of mechanical plastic strip I’m open to suggestions.

Thanks in advance