Exploiting habitat niches (as the pros would say) each in in its own way, a brown creeper and a white-breasted nuthatch explored the same ponderosa pine trunk.
The creeper, as creepers do, was going up. The nuthatch was coming down headfirst, as nuthatches do.
Who would give way?
In the bird world, size matters. David Sibley gives the average nuthatch a weight of 0.74 oz. (21 gr.) and the brown creeper a mere 0.29 oz. (8.4 gr.). No contest--the creeper flew away.
And, sitting in the woods, I was left thinking about the rule for mountain driving impressed on me as a kid: Uphill traffic has the right of way. (Because they need the momentum?) Does anyone still follow that rule anymore?