user_242798 (2020-05-24 19:39:26+00:00): Access, specified per vehicle type, is set by [traffic_sign=NL:G13] only. 
Therefore: (bicycle=yes), [moped=no], [mofa=no], [foot=yes] (RVV 1990, art 4, paragraph 2). 
Access, specified per vehicle type, is not affected by [opening_hours], "bird breeding season" or [barrier=gate] is closed. 
Gate closed means: 'closed' for All. 
Gate open means: 'open' for All. 
Therefore Deleted: 
- access:conditional=no @ (Mar 15-Aug 15) 
- bicycle:conditional=permissive @ (Aug 16-Mar 14) 
- foot:conditional=permissive @ (Aug 16-Mar 14) 
Redundant, complimentary, hard to maintain: 1x "(Mar 15-Aug 15)" & 2x "(Aug 16-Mar 14)". 
How to Render these three tags on the Map? 
During bird breeding season gates/access might be closed, or not. 
Therefore:  
SET [opening_hours=sunrise-sunset open; Mar 15-Aug 15 off "closed during bird breeding season skylarks; closing period may vary from year to year"]. 
This is one - only one - Tag which is also Rendered on the Map, giving all relevant information (to the user). 
Textual explanation is required to understand the closure. This is not an option in "*:conditional=" syntax. 
Closure period may vary from year to year. In this case, Soesterberg, I have seen different dates (see: Mapillary). 
Or, perhaps no birds are breeding, therefore no closure for this year. 
Or, white-tailed eagle will build two nests. Female will decide which nest to use. So, perhaps no closure is required for the other nest area. 
Terschelling (f.i.) will review each year which area will be closed, or not. 
The operator may decide that the closure will be lifted before the end of "official period" bacause breeding has been completed. Or they found out there was no breeding at all. 
[Seasonal=yes] is needless if [opening_hours] are specified. 
[seasonal] is to be used for a ferry not having [opening_hours] specified, but we are sure the ferry will be in operation all year, or season only. 
[Access/bicycle/foot:condional=permissive] is not (always) correct. For 'Vliegbasis Soesterberg', 'Landgoed de Paltz' (operator: Utrechts Landschap) it's not correct. 
Permissive access is defined as follows: "Open to general traffic until such time as the owner revokes the permission which they are legally allowed to do at any time in the future." 
This applies to private sector (legal persons under private law). A farmer might decide today ("at any time in the future") bicycle and/or foot is no longer welcome on his privately owned land. 
Under public law, an operator is bound to a management plan, a destination plan. This plan specifies who, which vehicles have access and under what conditions. 
Staatsbosbeheer, Natuurmonumenten, Zuid-Hollands Landschap, Utrechts Landschap are Public Law Organizations. 
Utrechts Landschap (I quote): "Yes we may revoke access, even today. But we need a good reason for doing so: storm (danger), urgent maintenance, or exceptional species (nature value). In all other cases we will have to start a discussion, provide arguments, set op meetings as to update/change the management plan. This is not 'permissive' as OpenStreetMap defines". 
Moreover: if all footways, paths, cycleways having an 'operator' are specified as 'permissive', this will clutter, hide, overshadow the 'real' permissive access. If I plan a hiking trip using a 'boerenlandpad' (over private farmland) I should always consider the possibility a path that was open last year, has now been closed for public access. 
But a cycleway + [traffic_sign=NL:G13] implies [bicycle=designated], even by law. 
It will take a lot of effort to revoke this access.