EASTERN BROWN-HEADED COWBIRD 425 



males, which were usually not in song and did not display. The 

 second group to come were the migrant males, passing through on 

 their way to points farther north; they were arriving and departing 

 at various dates ranging from March 20 to April 27. "These birds 

 usually are seen scattered among flocks of Red-wings, not forming 

 any solid flocks of their own kind. They come to the marshes to 

 pass the night with the Red-wings and the Rusty Blackbirds but 

 during the day scatter over the fields on the uplands, where, in small 

 groups, they forage for food." 



The third phase is marked by the arrival of the resident males, 

 which come on the average between March 23 and April 8. 



The resident males on arrival at once establish themselves on their posts and 

 remain in their territories for a few hours early in the morning every day, spend- 

 ing the greater part of the day in foraging around for food, often going to stubble 

 fields, and to plowed areas a little later in the season. As the season advances 

 they spend more and more time in their respective territories and at the time the 

 resident females arrive the males are spending at least half of each day within 

 the limits of their areas. * * * The testes of these resident birds are noticeably 

 larger than those of the migrants, and as all the birds collected at dusk in the 

 marshes averaged smaller testes than those shot from their singing trees, it seems 

 that the two groups do not associate in the marsh, the resident birds sleeping 

 in their territories. 



The migrant females are the first of that sex to arrive, passing to 

 more northern points between March 23 and April 28. At first they 

 appear as lone individuals among the flocks of migrating redwings, 

 grackles, and cowbirds, but later they pass through in flocks of a 

 dozen or more. 



The fifth group is made up of resident females, arriving between 

 April 3 and 11. "The arrival of these resident females acts as a 

 spark to set off the pent-up energies and passions of the males and 

 arouses them to an unbelievable frenzy. The persistence and de- 

 termination with which the resident males pursue these females 

 makes one wonder if either ever rest. The females evidently recog- 

 nize the limits of the territories of their respective pursuers as they 

 usually fly in wide circles closely followed by one or more males, 

 but do not leave the general vicinity of their territories. The ovaries 

 of these resident females are considerably larger than those of mi- 

 grant birds of the same date." 



The sixth and last phase of the migration marks the arrival of what 

 are apparently the immature males and females. "About the begin- 

 ning of May or even the last of April all the resident birds are estab- 

 lished and no more migrants are to be found coming in to the marshes. 

 There is a decided slump in the migration lasting until about the 

 second week of May when suddenly there appear numerous flocks of 

 Cowbirds of mixed sexes in the upland fields, around the cattle, and 



