The common alder is important to wildlife all year round and the seeds are a useful winter food for birds. Deer, sheep, hares and rabbits feed on the tree and it provides shelter for livestock in winter. It shades the water of rivers and streams, moderating the water temperature, and this benefits fish which also find safety among its exposed roots in times of flood. The common alder is the foodplant of the larvae of a number of different butterflies and moths and is associated with over 140 species of plant-eating insect. The tree is also a host to a variety of mosses and lichens which particularly flourish in the humid moist environment of streamside trees. Some common lichens found growing on the trunk and branches include tree lungwort ("Lobaria pulmonaria"), "Menneguzzia terebrata" and "Stenocybe pullatula", the last of which is restricted to alders. Some 47 species of mycorrhizal fungi have been found growing in symbiosis with the common alder, both partners benefiting from an exchange of nutrients. As well as several species of "Naucoria", these symbionts include "Russula alnetorum", the milkcaps "Lactarius obscuratus" and "Lactarius cyathula", and the alder roll-rim "Paxillus filamentosus", all of which grow nowhere else except in association with alders. In spring, the catkin cup "Ciboria amentacea" grows on fallen alder catkins.