The first sign that pecan buds are beginning to expand is a bud stage that is termed outer scale split. I took the photo at right back in 2013 to illustrate what exactly outer scale split looks like. Note that the outer covering (or scale) that surrounds a dormant bud splits open when the bud inside starts to expand. Eventually the outer scale is pushed off the end of the bud to reveal a tight green bud underneath.
I watch for outer scale split every year because this event coincides with the start of active tree root growth. Fertilizer is most efficiently taken up by actively growing tree roots so I make my Spring fertilizer application when I see outer scale split (I haven't fertilized yet).
I checked three pecan cultivars for signs of bud growth; Faith, Hark, and Kanza. The photos above shown three twigs with fully dormant buds. From past experience, Faith will begin bud growth several days before Hark and Kanza. But as of today, Faith buds showed no signs of expansion. Over the past few days we've experienced some mild daytime temperatures but our nights have still been chilly. It will take some warmer night time temperatures to wake up pecan trees from winter dormancy.