I would imagine that there might be many women out there who are interested in nature, birds, walking and female company. I imagine many of the target participants are aged over 60 and they might well have (1) had enough of men, and (2) not wish to turn up at a car-park in the middle of nowhere and find that it is them and a bloke that are the first two to have turned up.
Men need to start turning up at events for women that invite men to turn up. We need to turn up and say our piece, and then leave. If there's a trans'woman' there we can instead spend all of the event as close to him as possible talking about football and beer and classic cars and steam trains (though I note that one famous trans'woman' barrister who has frequented this board is interested in at least three of those stereotypically male interests - as he is perfectly entitled to be, and would entitled to be if he was a woman).