Little Slowdown in the Heat

Do birds eat less in the heat of the day? For a long time I thought so. But hard data have convinced me that this really isn't true. Here's a plot of the total number of BirdCam photos taken at a suet feeder in 60-minute slices through July 14, 2010. This day started relatively cool, and we had a thermometer reading of only 84 degrees at 11:15 AM, but clouds parted and the peak heat of the day was 91 degrees F near 5 PM. One can see that there were two very active periods (8-9 AM and 12-1 PM) and one fairly busy one (10-11AM) but otherwise consistent activity was recorded between 6AM and 6PM. Suet feeders were every bit as active at 3PM as at the cooler 7AM. Nor did we see only heat-hardened birds out in the late afternoon (I think of a neo tropical migrant like the Catbirds), as the year-rounders like Eastern Bluebirds, House Finches, Carolina Wrens, Red Bellied Woodpeckers, and Downy Woodpeckers were out there as well. At least on this day upward changes in temperature didn't slow down the activity. Just goes to show that those high metabolisms still need fuel regardless.