05/01/2006 Council Packet - Laserfiche WebLink

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• • Brief background on Great Blue Herons Great Blue Herons (Ardea Herodias) are the largest North American heron and are widely distributed. In Minnesota, Great Blue Herons return each spring about March 17th and lay eggs by about April lst. Chicks typically hatch around May 1st. Clutch size ranges from two to five eggs. Fledging occurs around July 4th. Wild Great Blue Herons can live up to 20 years. Their diet consists primarily of fish, but they will opportunistically take other prey including small birds, rodents, amphibians, and invertebrates. Visual hunters, Great Blue Herons usually hunt by slowly walking or wading in order to stalk their prey. They may also stand motionless and wait for prey. Similar to other heron species, Great Blue Herons occasionally plunge dive for fish in deep water (Kelly et al. 2003, Hawkins 2003). For the most part, Great Blue Herons are diurnal hunters, but on occasion will forage nocturnally (Butler 1992). Great Blue Herons are shy and easily disturbed. As such, they prefer nesting in remote and inaccessible locations. These locations typically include islands, wetlands, or riparian zones. Within this habitat, their preferred nesting locations are situated within the uppermost canopy of mature hardwood forests (Figure 2). Given their inaccessible nest locations and timid nature, monitoring heron colonies is not only logistically difficult, but also risky for the health of the colony. Disturbance within the colony can cause abandonment early on in courtship /nesting and, later on, may cause attending adults to leave the nest long enough to render eggs /chicks vulnerable to exposure or predation. Figure 2: A climber installs cameras in the crown of a Black Ash on Peltier Island. Camera height was estimated to be 75 feet. Cameras installed at Pig's Eye Lake were 100 feet high. 3