I use "High-energy Suet" from Lowes which I buy by the case since it goes so fast. It gets a little soft at temperatures above 70 or so but the birds don't seem to mind and it's never gone rancid on me. The main customers for most of the fall and winter are starlings, flickers, Downy Woodpeckers, kinglets & yellow-rumps but just about everything feeds on it occasionally, particularly during cold snaps: quail, scrub-jays, chickadees, White-crowned Sparrows, finches, House Sparrows.