Firlefanz, my understanding is that the male is usually the first to arrive at the nest.
In earlier years, we have recognised that Tiit has a darker coloured beak. This black stork has an almost black area of his beak.
When we see Tiina, or which female partner will join him, then we can decide other differences between them
I do hope Tiina arrives quickly.
I see that Tiit is concentrating on the centre of the nest - preparing a nest bowl is important.
In 2011 Tiit was the last to leave the nest, next spring it was Tiina the first to arrive. Last year Tiina left the nest last and now Tiit arrived first.