Northern Prairie Wildlife Research Center
Breeding Range. (Fig.16). At present most of the breeding colonies of Great Blue Herons in North Dakota are found along the margin of Lake Sakakawea or Garrison Reservoir including the Snake Creek arm and the Little Missouri arm of the reservoir. A few breeding colonies also have been reported in the Turtle Mountains within Rolette and Bottineau Counties, and small colonies have been found on the Upper Souris and J. Clark Salyer National Wildlife Refuges. One recent colony also was found in the newly flooded forest near the upper end of Oahe Reservoir below Bismarck.
Apparently, Great Blue Herons were breeding in the wooded bottomlands along the Missouri River prior to the establishment of the giant reservoirs. Audubon (1897) recorded this species on June 5, 1843, along the Missouri River, between Badger Creek (a few miles below Fort Rice) and the mouth of the Heart River. Larson (1928) reported that this species was a common summer resident and breeding along the Missouri River in northeastern McKenzie County during the period 1912-1926.
Occasional observations of adults have been recorded elsewhere in the state during the early part of the breeding season. Whether or not any or all of these records represent breeding birds is somewhat questionable since post-breeding vagrants, probably from the south and east of North Dakota, appear quite regularly throughout the state during the period extending from late June to early September.
Breeding Habitat. Breeding populations of Great Blue Herons were usually associated with Double-crested Cormorants on their nesting grounds. These mixed colonies were located in stands of large dead trees that had been killed because of rising waters of reservoirs or managed waterfowl impoundments. The clustered nests were constructed chiefly of small sticks and twigs and were situated near the tops of the dead trees. This temporary type of nesting habitat often persisted for only a few years because the nesting trees gradually became decayed and were then felled by strong winds or wave action. George W. Enyeart reported that most of the Lake Sakakawea colonies were represented by peak populations during 1956-1965 when many colonies, each containing dozens of pairs or more, were present. Owing to deteriorating conditions of nesting habitat since that time, the numbers present have gradually diminished and a few colonies have disappeared. It is probable that a few new colonies are or will be established in the recently flooded forest along the Missouri River toward the upper end of Lake Oahe Reservoir below Bismarck.
Nesting. The breeding season probably extends from late April to early August. On April 27, 1948, each nest in a colony on the J. Clark Salyer National Wildlife Refuge contained 1 egg (M. C. Hammond). Four sets of eggs containing four eggs each were collected from a colony of about 30 pairs in the Turtle Mountains by G. A. Withey and G. C. Withey; two of these sets were taken on May 8, 1925, one on May 9, 1926, and one on May 15, 1926. On June 11, 1946, seven to ten nests in a colony on the J. Clark Salyer National Wildlife Refuge contained good-sized young (M. C. Hammond). On August 2 and 4, 1920, a family of four was seen at Lake Upsilon in the Turtle Mountains, Rolette County (Wood 1923).
 |
| Figure 16. Breeding Range of Great Blue Heron. |
 |
|
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://www.npwrc.usgs.gov/resource/birds/bbofnd/species/1940.htm
Page Contact Information: Webmaster
Page Last Modified: Thursday, 03-Aug-2006 11:25:06 EDT
Menlo Park, CA [caww54]
