Jennings Environmental Education Center, Route 528 near the intersection of Routes 8 and 173, Slippery Rock, will host a guided walk at 2 p.m. Sunday. The 90 minute hike will focus on the transformation of trees and the environment during the fall season. Jennings is open from sunrise to sunset for hiking. Call 724-794-6011 to confirm programs.

<B>Armstrong Rails to Trails Association</B> and the Allegheny Valley Land Trust will have a 31-mile fall bicycle ride on Saturday. The ride will start 1 p.m. at the northern end of the Armstrong portion of the trail in East Brady and end in Rosston. The registration fee is $5, or $15 if the rider takes a ferry ride to East Brady. Reservations are required. Call 724-543-4478 or 724-526-3552.<B>McKeever Environmental Learning Center</B>, 55 McKeever Lane, Sandy Lake, will host a leisurely walk and program about bird migration at 7:30 a.m. Saturday. Admission is free. Call 724-376-1000 or visit www.mckeever.org.