BREWER'S BLACKBIRD 303 



Previous to that time it was either not present or so rare as to have 

 escaped observation. Now it is a common summer resident, breeding 

 in colonies throughout the state; absent or rare as a nesting bird in 

 most of the southern counties." 



"The presence of the Brewer's Blackbird in Wisconsin prior to the 

 years 1926 and 1927 was rare," writes Schorger (1934), who remarks 

 that "the recent extension of its range is quite remarkable." The 

 year 1926 marked the beginning of the influx, and Schorger says that 

 "it is now possible to state that Brewer's Blackbird is at present a 

 common summer resident, breeding in a narrow area extending from 

 Polk County in the northwest, to Walworth County in the southeast." 



I (1952) carried on a behavior study of this species principally at a 

 breeding colony, "the river-mouth colony," at the mouth of the 

 Carmel River, Monterey County, on the central coast of California, 

 for six breeding seasons from 1942 through 1947, with check obser- 

 vations in 1948. The colony is situated at the edge of a marsh. The 

 birds nest in Monterey pines (Pinus radiata) which, although native 

 to the region, are planted along the streets of a subdivision adjacent 

 to the marsh, on what was originally chaparral land. Although the 

 birds forage on lawns, streets, and food-trays, they spend a large part 

 of their time on the marsh area, undisturbed during the years of this 

 study. Tules (Scirpus), which grow in patches on the edge of the 

 marsh, as well as the pines, are used for roosting and daytime resting 

 places. Electric light wires and poles along the streets are used for 

 perching by the flock as well as for display and guard perches by 

 individual birds. 



In the study, 318 Brewer's blackbirds, 158 males and 160 females, 

 were color banded. Over the period of study, 117 marked birds bred 

 in the colony; in addition to these there were 8 birds of each sex 

 entering into the breeding activities of the colony that I was unable 

 to band. Many of the remaining 201 banded birds were found at 

 other colonies in the region at various seasons, and some of them were 

 found breeding at those places. The banding station was main- 

 tained throughout the year near a house in the center of the colony. 



The breeding period, which extends roughly from the end of Janu- 

 ary into July, may be divided into the following phases of activity: 

 1. segregation and assortment into pairs — pair formation; 2. nest- 

 building, copulation, and egg-laying; 3. incubation; 4. nestling care; 

 5. fledgling care. 



Spring and courtship. — In phase 1 old pairs (that is, pairs return- 

 ing from the previous year) reassociate and new pairs are formed. 

 By "new" is meant some combination involving either young birds 

 in their first year, birds banded during the season (ages could not be 



