What do you think the six objects in the central rosette represent most likely?

[nablator]

Sure, it has nothing to do with the picture. The text still belongs to the previous page.
"als die Frösche hant getan, des müssentz noch in Sorgen stan"
When the frogs did it, they must still be in trouble.

Right. The text of the fable is under the illustration, not above.

I found a translation (not helpful to understand the peculiar illustration):

Fable no. 26: Of a Harrier and Pigeons
On evil constables

Once a big fight broke out
which deeply upset many birds, 
as the following fable tells us.
The harrier had announced war
5 against the pigeons, which created many problems for them
because they were afraid they might have to die.
They could not find any safety
from the harrier, so they suffered great pain
and anxiety; in their hearts
10 they were terrified.
They all got together in a council
and they all agreed
that they would not be able to survive
without a constable, which was, as they determined,
15 the hawk which was very powerful.
It would certainly defeat the harrier
and would help the pigeons in their suffering
so that they would not all die.
When the hawk had become their constable,
20 it quickly fell back to its nature
and displayed its aggression:
the pigeons were all lost,
none of them could survive.
The one who was supposed to be their protector
25 was their enemy. The sheep are lost
when the wolf becomes the shepherd.
The harrier’s announcement of its military threat was better
for the pigeons than the hatred of their own constable.
When people want to achieve something
30 and keep the goal in mind,
then they will hardly fail in that,
whether they are women or men.
To him who must make a choice between two evil persons,
let me give this advice
35 that he chose (this will be to his advantage)
the one who will cause less harm.
When the one is chosen as the protector
who destroys the people then,
both women and men will be lost.
40 No one can protect himself from that person.