Now, even in the-dead-of-winter, the great blue heron frequently is seen standing and stalking its prey for long periods of time in shallow water along the edges of lakes, streams and ponds, even Bayer pond.

The bird withstands this cold-water wading with what we call “regional heterothermy” and by using a vascular “counter-current mechanism.” In the field of study of how animals adapt to adverse conditions, the standard mantra is: an adaptation need not be elegant, only adequate.

In the long thin legs of the great blue heron, the vein (or veins) bringing blood back from extremities toward the heart lies alongside of (or many venous branches wrap around) the artery taking warm oxygenated blood to the extremities. This close proximity allows much of the arterial blood heat to move into the venous blood and be carried directly back toward the body’s deep core. Maintaining the deep core body temperature is important for birds just as for us. The normal body temperature for many birds is in the 102-104 Fahrenheit range. Some are higher.

These adaptations for cold-water work are seen in many wading birds, in gulls, in the European rook, a member of the crow and raven family, and probably in other bird species not yet studied.

The result is that various areas of the bird’s body are allowed to become much colder: regional heterothermy. Leg muscles, other tissues, and enzyme systems become acclimatized to work at the low winter water temperatures of such as Bayer Pond. The fish population is reduced with each heron visit.