The center trunk of this tree is hollow inside and no doubt harbors insects that many birds enjoy!
Look closely at all the holes and you can see how many woodpeckers have been enjoying this dead Roseapple trunk!
Even a log on the ground will attract ants, beetles and other insects that lizards and other small animals will use as a food source.
Here a larger animal (maybe gopher tortoise?) has made a burrow under the trunk of a fallen live oak.
Leaving a little dead wood in your yard not only saves you the labor of removing it, but it will increase your enjoyment by attracting a variety of wildlife!
For additional tips on attracting wildlife to your yard, see: http://edis.ifas.ufl.edu/uw175