Food items obtained from the stomachs of great blue herons are listed in 

 appendix B. Those foods, though diverse, indicate that fish are an important 

 food item of herons feeding on the river. Herons were observed feeding along 

 banks and island margins in deep and shallow water, and those collected for 

 food habits analyses were taken in both types of sites. 



WHITE PELICANS 



During the spring migration period, white pelicans [Peleaanus 

 erythrorhynchos)were observed on the lower Yellowstone between Pompeys 

 Pillar and Fairview. Their summer distribution was limited to areas down- 

 stream from Miles City, particularly from the mouth of the Powder River to 

 Fairview. These summering pelicans are believed to represent nonbreeding 

 birds from the Medicine Lake colony in northeastern Montana because most 

 banded birds found dead during the study had been banded at Medicine Lake. 

 John Martin (1975) estimated there are approximately 1,500 breeding pairs 

 of pelicans in that colony. The migration routes of those birds and of 

 those from the breeding colony at Lake Bowdoin National Wildlife Refuge in 

 northcentral Montana may account for the higher number of pelicans observed 

 in areas east of Miles City. Peak counts during the spring migration period 

 showed between 300 and 450 pelicans present in the study area. During summer, 

 numbers decreased to between 100 and 200 birds. 



Pelicans collected or found dead on the river were examined to determine 

 their food habits (appendix B). Stomachs of those birds revealed utilization 

 only of Cyprinids. Pelicans feeding in shallow water along the river appeared 

 to be taking fish primarily. Cooperative feeding by pelicans (Hall 1925) was 

 observed along banks near Intake and Terry. As described by Hall, when fish 

 were found in shallow water near shore, groups of pelicans aligned themselves 

 in a semicircle, working toward shore, beating the water with their wings 

 and feet. When they reached shallow water near shore, the participating 

 pelicans scooped up the fish. Fish concentrations below the Intake diversion 

 may attract pelicans to that area from spring through late summer. Cold 

 weather in early fall induced pelicans to leave the river until the following 

 spring. 



Instances of pelican mortality on the river were observed on several 

 occasions. One bird was found shot through the wing near the Terry bridge. 

 Pelican flocks near Intake were also reportedly fired upon. According to 

 Diem and Condon (1967), shooting is a major mortality factor of the Yellowstone 

 Lake pelican colony. On the Yellowstone River, more pelicans appeared to die 

 from causes other than shooting, including drowning. Feeding pelicans 

 apparently caught their bills on roots and submerged tree limbs and eventually 

 drowned. Others were found dead on bar and island loafing areas, the causes 

 of their deaths unknown. 



DOUBLE-CRESTED CORMORANTS 



Double-crested cormorants [Phalacrooorax auritus), present in the study 

 area from spring through midfall, were most common during spring migration 



62 



