I know, from this question it is not illegal to be on private property without permission if you do not know and could not reasonably be expected to know that it is private property. Does this apply to hunting as well?
Aside from the law regarding trespass, ORS 498.120 specifically forbids hunting on another’s cultivated or enclosed land. The land need not be fenced or posted with "No trespassing" signs:
For the purpose of subsection (1) of this section, the boundaries of “enclosed” land may be indicated by wire, ditch, hedge, fence, water or by any visible or distinctive lines that indicate a separation from the surrounding or contiguous territory,
Apparently hunters have some obligation to be aware of private land boundaries in the areas they hunt. The degree of this responsibility is something that is still regularly disputed in court. In the linked case of State v. Hinton, a hunter was convicted of criminal trespass with a firearm. This was prosecuted as a violation rather than a misdemeanor which reduced the state's burden of proof to a preponderance of the evidence. The hunter moved for a dismissal, claiming that the state hadn't proved that a reasonable person would have known they were on private land:
The evidence presented at trial shows that there was nothing about the border between BLM land and the GI Ranch where defendant walked that would cause a reasonable person to believe that permission was required to enter. The landscape was the same. There was no fence. There were no signs posted. The border between the GI Ranch and the BLM [land] was in the middle of thousands of acres of the high desert of central Oregon.
The circuit court denied the dismissal, and the hunter appealed. The Oregon State Appeals court affirmed the circuit court's rejection of the dismissal:
Specifically, the record provides ample evidence that, using maps, people in this area can determine generally where they are and whether they are on GI Ranch land or BLM land. To be sure, they may not be able to know "the very second" that they cross onto private land. But, viewed in the state's favor, the record establishes that reasonable people can know generally once they have made the crossing.
There is a difference between unlawful and a crime. For instance, there isn't much doubt that Hilary Clinton's handling of emails was unlawful. However, James Comey came to the conclusion that there was an intent/mens rea requirement for criminal prosecution that he could not prove to a high enough certainty to justify prosecution.
Some sort of such requirement is generally present for an action to be a crime. I don't know of any strict liability crimes that arise out of hunting on someone else's property, but in cases of negligence, it could easily be a factor. For example, if a hunter shoots a land owner on the land owner's property, without having the land owner's permission to be there, the fact finder could easily find this to be an aggravating circumstance.
There could also be non-criminal consequences for the activity, such as a civil suit or loss of a hunting license. There are much lower, and often non-existent, mens rea requirements for non-criminal proceeding such civil or administrative. If a statute requires that the defendant's conduct be unlawful for something (such as a civil remedy) to apply, then the presence without consent would satisfy that requirement. The unlawful nature would also make it easier, should the land owner decide to engage in violence against the hunter, for the land owner to pursue a self-defense argument: in some circumstances, one is allowed to use violence against those that are engaging in unlawful activity, even if that person is not aware that their activity is unlawful.
Trespass is knowingly entering another owners' property or land without permission, which encroaches on the owners' privacy or property interests. law.cornell.edu/Wex definition of "Trespass"
In an attempt to address the issues behind the question, go beyond legal technical issues to add a bit of common sense, as well as adding a somewhat-cynical speculation that an answer of "yes, it is legal to accidentally hunt on private property" would lead to a significant number of... convenient accidents:
It seems to me that:
- If hunting without permission on private property, you are violating property boundaries, knowingly or not.
- You may be reasonably expected to know that there are such things as private property boundaries.
- You are taking a risk by not keeping to public lands.
- If you are indeed doing it by accident, are very polite and apologetic, seem perfectly willing to vacate if they don't want to give permission, the land-owner is convinced it was unintentional, AND it's not a hot-button issue for them, seems like penalties might be just a verbal warning.
- OTOH if they are pissed off about e.g. the last twenty seven guys who left trash, shot up outbuildings (apparently some 'hunters' will shoot at explosives magazines for entertainment), shot their car, equipment, pets or livestock, or they are a conspiracy theorist, or like wildlife, or they've had problems with theft or vandalism, seems like you could be arrested, greeted with the muzzle of a firearm or even be shot.
- Figure every time they find a trespasser or damage done by one, it uses up a bit more of their tolerance. Hopefully what they do about it is just post "NO TRESPASSING" signs and put up a fence.
Unless there are clear signs and/or marked boundaries or it is "cultivated" land, it seems that purely "accidental" trespass to hunt may be permitted in the absence of any law expressly prohibiting it.
eRegulations, which styles itself as an "official regulations" site, states:
It is unlawful to hunt on private property without permission from the landowner. See ORS 105.700 and 498.120.
However, this seems incomplete as the cited statutes impose a requirement on the landowner to enclose their land in a prescribed manner:
... a plaintiff who is a landowner shall receive liquidated damages in an amount not to exceed $1,000 in any action in which the plaintiff establishes that:
(a) The plaintiff closed the land of the plaintiff as provided in subsection (2) of this section; and
(b) The defendant entered and remained upon the land of the plaintiff without the permission of the plaintiff.
(2) A landowner or an agent of the landowner may close the privately owned land of the landowner by posting notice as follows:
[it goes on to state the requirements for the placement of signage]
ORS 498.120 Hunting on another’s cultivated or enclosed land similarly states:
(1) No person shall hunt upon the cultivated or enclosed land of another without first obtaining permission from the owner or lawful occupant thereof, or the agent of such owner or occupant
(2) For the purpose of subsection (1) of this section, the boundaries of “enclosed” land may be indicated by wire, ditch, hedge, fence, water or by any visible or distinctive lines that indicate a separation from the surrounding or contiguous territory, and includes the established and posted boundaries of Indian reservations established by treaties of the United States and the various Indian tribes...
NB What counts as "accidental" will depend on the particular circumstances, including what can be shown about the hunter's previous "accidents" in similar circumstances.