there is not any time that is a for sure time since they are seen during different times on different days and what is seen varies by the season also.  Right now being so hot during the day, it does seem to me anyway that the mornings and evenings are better as they seem to stay in the shade during the heat of the day.  you can get an idea of what is seen and when by looking at the daily pictures threads which can be found HERE as pics will usually be posted soon after the sightings.   From the sightings logs you can see when particular animals were seen and pics posted. For those click here I hope this helps.