Great blue herons probably did not nest along the Hanford Reach of the Columbia River in the 1800s because of the scarcity of trees. Trees were first introduced to land along the Reach with the advent of irrigation farming in the early 1900s. Since 1950 most of the heron colonies distributed along the Hanford Reach have elected to nest in clusters of non-native trees planted 80 to 100 years ago at scattered farmhouse locations. These sites have been protected from most human intrusions by the safety and security provisions enforced by the U.S. Department of Energy?s Hanford Site since 1943. Reproductive success of Hanford Reach colonies is equal to or better than that of heron colonies elsewhere in the Pacific Northwest. In recent years the number of active heron colonies along the reach has declined. The causes of the observed decline are unknown to us.
Revised: August 24, 2004 |
Published: October 1, 2003
Citation
Rickard W.H., and B.L. Tiller. 2003.Observations on the Nesting Distribution of Great Blue Herons on the Hanford Reach of the Columbia River.Northwest Science 77, no. 4:357-360.PNNL-SA-36329.