The Rufie Chronicles: Morning Data Graphs

Temperature each morning and time of day that Rufie appeared at Gerry's feeder. Click on each graph to see larger version with scale and legend.

Temperature can fluctuate a great deal during late fall and early winter, as the first graph shows. In the second graph, although there are many exceptions from day to day, the time Rufie appears each morning seems to grow later throughout the time period. What is happening to the time of sunrise during this time period?