I’m new to citystrides. It strikes me that people covering a large number of streets are in a good position to also be collecting data for all sorts of things.
So, my question is: is anyone doing anything else while visiting their city’s streets, like taking photos of trees, or recording bird song, or documenting something else??
Fixing issues with the OpenStreetMap data 
yeah fixing the map but also looking at urban history. In the UK we have 40+ maps from 1830 to 1970’s online. I really enjoy exploring the area then coming home and seeing how the local area has changed and in some cases from mining / farming to housing in 50 years. Some times old walls / buidlings remain other times it just road names or alley ways cutting across the estate
Ground truthing street names, public paths, parks, schools, stop signs, and other info for OSM and taking photos to create a sort of visual archive.
Updating OSM as others have mentioned, photo walks, also once I had to survey the flat counts in various types of apartment blocks for my thesis