Shagbark hickory shedding leaves early
Apologies for the delayed response. There are many reasons why the tree would be shedding leaves early, including drought and early cooler night temps. In what county are the trees located? Was there any construction damage to the yard around the trees? Or, did heavy equipment drive over the roots of these trees? Driving heavy equipment over the trees could have compacted the soil, making the roots have to work harder to pump water to the tops of the trees. If there was heavy equipment around the trees, you may want to contact an arborist to assess the situation prior to dormancy this year. You can use this tool to find a certified arborist in your area: https://www.treesaregood.org/findanarborist
If you would like to talk in more detail about the condition of your trees, feel free to contact me directly using the information below, or by replying to this thread.
With hopes the trees continue to be healthy and vibrant for a long time to come!