Hello Sharon,

This is not an uncommon phenomenon for Tulip Poplar. The cause is difficult to determine, but may be what is referred to as "slime flux." Here is more information: https://extension.umd.edu/resource/tree-trunks-wet-wood-or-slime-flux

No action needs to be taken unless the canopy shows signs of dieback, thinning, or discolored leaves. If you are concerned, or if anything worsens, you can have it assessed by a certified arborist. Some work with tree-care companies and others work independently. Here are two search tools for finding an arborist, if needed:

https://dnrweb.dnr.state.md.us/forests/tree_expert_search.asp

https://www.treesaregood.org/findanarborist/arboristsearch

Miri