Stake makes a great point here about the work light ratings... safety is a major factor when dealing with heat lamps!
On the topic of safety: When I was more heavily into fishkeeping, I used to use these as tank lights with really huge CLFs (150-200 watt equivalents) in them. Cheap, effective. But DO NOT TRUST THE CLAMPS. In our case it was a question of water/electicity safety. Not a huge danger with proper grounding and some GFI outlets.
A heat lamp bulb on the other hand will retain heat for a short time even after the electricity fails, possibly enough to start a fire if it is knocked over. I highly recommend a secondary stand or attachment method. A few simple wire loops (or some hanging chain) and a u-stand would do the job more than well enough and provide peace of mind and safety for both your chicks and your home.