Figure 3.

Bill surface temperature in thermoneutral (TN) (25°C) and cold-acclimated (CA) (5°C) ducklings obtained from thermal images. Representative thermal images are depicted in the top panel. The lower traces show the marginal model fits (±s.e.) for the TN- (a) and CA (b) duckling. Bill temperatures declined during the first 3 days of fasting in TN ducklings, while remaining constant, but lower in the CA ducklings. Bill temperatures during re-feeding were similar to those prior to fasting, although in the CA ducklings fluctuated heavily as shown in the sample thermal image.