YELLOW-HEADED BLACKBIRD 119 



considerable extent upon immatures at night." Errington reported 

 that from the spring of 1933 to July 1935, 280 great horned owl pellets 

 were collected, many of them taken when no yellowheads were 

 present; of these, 27 contained a minimum of 36 yellowheads, of 

 which at least 6 were young. From the gullet collections of the 

 young from 12 marsh hawks' nests, during three seasons, 26 specimens 

 of yellowheads were identified, 5 of which were young. Of the other 

 two predators, Errington has this to say: "Foxes take a variable 

 number of Icteridae other than meadow larks, but I believe that red- 

 wings are more apt to occur in their diet than yellow-heads. * * * 

 The muskrat often has a meat tooth and may very well eat blackbirds 

 it finds freshly dead or may even kill an occasional cripple or a very 

 immature bird that it may find in the water or in some similarly 

 accessible place. However, as an active predator upon blackbirds, 

 I would not say that it rates at all." 



Ammann (MS.) adds: "The three largest of the known destructive 

 agencies were a rise in water level of the lake, a cold rainstorm, a 

 short, violent windstorm. They accounted for the loss of 28.7 percent 

 of all nests and 31.7 percent of all eggs and young (using the total 

 number of eggs as a basis for the latter figure). * * * Internal para- 

 sites were found in the alimentary tract of 21.4 percent of the 117 

 specimens examined. Acarina were found in 17 percent and Mallo- 

 phaga of four species on 59 percent of the 122 specimens examined." 



Fall. — Fautin (1941a) writes: 



During the molting period which began in July the Yellow-headed Blackbirds 

 left the nesting areas and congregated in large flocks in marshes where the growth 

 of cattails, Typha lalifolia, and bulrushes was most dense. Here they remained 

 very much in seclusion during the greater part of the day, coming out only in the 

 mornings and evenings to feed. Very often the males were found in one part of 

 the marsh and the females and juvenals in another. This association of the 

 females and juvenals may have been due to the greater attentiveness of the 

 females to the young during their nestling period. * * * 



When the autumn molt was near completion, about August 1, the Yellow- 

 headed Blackbirds, together with other species of blackbirds, came out of hiding 

 and roved about in the fields during the day, returning to the cattail marshes to 

 roost at night. 



Migration began about September 1. By September 7 only three females 

 could be located in the vicinity of the study areas. One week later a single 

 juvenal male in a flock of about fifty Brewer's Blackbirds, Euphagus cyanocephalus 

 cyanocephalus, was all that could be found and by September 17 all had left the 

 vicinity of the study area. 



Mrs. Bailey (1902) says of the fall wanderings: "From their breed- 

 ing grounds in the sloughs and tule marshes the yellow-headed 

 blackbirds scatter out and wander over the whole of the western plains 

 country, appearing in flocks with grackles, red-wings, or cowbirds in 

 the characteristic hordes of the fall migration, or in flocks by them- 



380928—57 9 



