176 BULLBTIN 191, UNITED STATES NATIONAL MUSBUM 



make the first move, but once it is made tlie remaining birds rush to' 

 follow. 



Daily routine of activity in the yellow-billed magpie is, perhaps, more 

 easily traced than in most other birds, mainly because this bird is so con- 

 spicuous. Also at many places the magpies are so continuously and so 

 easily accessible for observation in the vicinity of human living quarters 

 that it is possible to trace the daily and seasonal changes year alter 

 year. Thus it becomes obvious that while the daily program is fairly 

 rigid it is also highly variable. 



The recorded program of the magpies on a normal day begins with the 

 arrival of the flock, as a unit or in sections, from the roost. After a 

 reassembly in trees, the birds scatter somewhat and begin to forage. 

 Late in the morning they retire to trees for a midday rest, which is 

 broken for another period of feeding before they form another group to 

 fly off to roost. Through the main part of the nesting period this be- 

 havior is modified considerably by the necessity of keeping close to 

 the nests. 



Magpies regularly congregate to roost in a group through most of the 

 year outside the nesting season. The site oftenest used on the Hastings 

 Reservation is in a small ravine about a hundred feet wide, facing the 

 west, and grown over with live oaks. The magpies roost in these dense 

 trees. Each night, nearly an hour before finally settling at the roost, 

 the birds assemble in sycamores or oaks in the canyon or the low hills 

 a quarter to a half mile to the north of the roost. Half an hour after 

 congregating, they fly to the roost. The assembling flock seems to be- 

 come more and more unified, the longer the birds stay. Often there are 

 squabbles with other birds, as crows or hawks, in which the whole group 

 participates, at least vocally. 



For 10 or 15 minutes preceding the flight across the canyon the mag- 

 pies are rather silent. They perch mostly in tree tops, several in a tree, 

 and there is little foraging. This period is followed by a series of out- 

 bursts of calls or a single one. Large groups make greater outbursts. 

 The flight then begins. After a few outcries the birds become quiet as 

 they fly more slowly and gain altitude steadily. The destination of this 

 flight is a group of trees, usually leafless black oaks, used as gathering 

 places both morning and night. Ten or fifteen minutes are required for 

 all the birds to make the flight. Cold, strong wind, cloudiness, and rain 

 tend to advance the time of flight across the canyon. Encounter with 

 some other species tends to delay it. Change of roosting place from a 

 common gathering place outside the normal daytime range of the colony 

 to the nest site occurs usually in January. 



Response to disturbance on the long flight to the roost is indicated 



