Free citizen science apps recommended by librarians. Find them in your app store:
iNaturalist - iNaturalist helps you identify the plants and animals around you.
eBird - record the birds you see in the field, and seamlessly link these observations with eBird--a global online database of bird records.
LeafSnaps - take a picture and identify the plants you see in your built and natural environment.
Zooniverse - The Zooniverse is the world’s largest and most popular platform for people-powered research across the scientific fields.
ArcGIS - this page offers a list and descriptions of user-friendly apps.