in the absence of a trunk or stone to lean on, a capybara may be an option;
I have observed these two individuals do this twice;
see also
https://www.inaturalist.org/journal/nelson_wisnik/21258-the-friendly-capybara
Not sure what is going on but this is the fourth birder that I know of who has had a phoebe perch on their binoculars or on their person at Commons Ford.