Eggs or? ID please

[Goldie M]

Took this photo at Sefton Dunes, alot of the leaves were covered with it . The tree next to it had nothing on it so it made me wonder what it was. Goldie

[LauraS56]

They look like galls to me. What's the tree, I remember some balsam poplar there (gorgeous smell in spring from the young foliage), could it be that? It looks too shiny to be hazel though the leaf shape is similar.