When comparing the nest sizes of great blue herons and eagles in the same area, new nests are relatively similar in size. A new great blue heron’s nest typically measures around 20 inches to 2 feet in diameter, while a new eagle’s nest has a diameter of approximately 3 feet.

However, as time progresses, eagle nests have the tendency to grow significantly larger each year. Eagles often incorporate larger building materials, such as wrist-sized pieces of wood, resulting in nests that appear bulkier and possess greater mass. A single eagle family may utilize the same nest for multiple generations spanning several decades. These nests can expand to an outer diameter of approximately 4 meters and weigh hundreds of pounds. The largest recorded eagle nest had an outside diameter of around 10 feet (although wider ones have been found) and an astonishing thickness of about 20 feet in the middle, weighing approximately 6,000 pounds (3 tons), which places a considerable burden on the supporting tree.

On the other hand, a great blue heron’s nest typically has a diameter of around a wingspan (approximately 4 feet), a central thickness of 2 to 4 feet (sometimes more if it is quite old), and generally weighs 100 pounds or less.

Both bird species reuse their nests across generations, leading to an increase in size with each successive year. Eagle pairs often return to the same nest annually for an extended period, while great blue herons may not always revisit the same nest in a rookery every year. Consequently, some heron nests accumulate additions year after year, while others may remain unused for a period and receive infrequent additions.