YBLLOW-BILLED MAGPIB 167 



collection of over 30 sets; some eggs were short and rounded, while 

 others were long and elliptical. 



A set of eight fresh eggs ranged in weight from 7.6 to 8.8 grams, 

 average 8.3, thus being considerably lighter than eggs of black-billed 

 magpies. 



Young. — Length of incubation period for the yellow-billed magpie is 

 not definitely known but is assumed to be close to that of the black-billed 

 one, or around 18 days. 



Hatching of the young apparently changes the magpies to silent birds. 

 One pair c.arried food to a nest at least 10 times in the 40 minutes it 

 was watched on the morning of April 12, the visits thus averaging four 

 minutes apart. Usually it was not possible to distinguish any objects in 

 the bill, but once or twice supposed large insects could be seen projecting 

 from the bill. The birds flew directly toward the site, but they perched 

 on some limb 3 to 10 feet away and toward the main crown of the tree 

 for a few seconds before going into the nest. The birds always entered 

 the nest from the same side and left through the opposite one. Nearly 

 always when one of the parents left the nest it flew directly to the ground 

 and immediately began to search for food. On this date whenever a 

 parent visited the nest, the young birds made calls that c.ould be heard 

 by a person 60 to 75 yards distant. These calls began when the parent 

 entered the nest and they ceased as soon as it left. Once, both adults 

 arrived at, and entered, the nest at about the same time. They flew away 

 together a few seconds later, and one of them dropped a fecal sac from 

 its bill when it had gone 50 yards. \ 



These adults nearly always flew to a nearby orchard to forage, and 

 four-fifths of their trips were to some freshly disked ground. On several 

 trips one of the parents perched in the top of an orchard tree before 

 going to the ground. They usually were silent, but once or twice a short 

 series of notes was heard at the nest. The time spent at the nest on 

 each visit averaged between 10 and 20 seconds. 



Apparently typic.al behavior of a family of six young out of a nest 

 and being fed by parents was watched for an hour near the time of nest- 

 leaving. At first three of the young birds perched in a tree 30 yards 

 from the nest. Later this tree held four young and two were in the nest. 



The usual procedure in feeding on this day was for the young to 

 keep a sharp lookout and, whenever an adult magpie came within sight, 

 to start up a series of loud calls, higher in pitch than those ordinarily 

 given by adults. If the approaching adult were not the parent of this 

 brood, it continued on its way, and as soon as it had passed the cries 

 would cease. If the approaching bird happened to be one of the parents, 

 it would go to the group of young birds and the cries would be con- 

 tinued until a young one had been fed and the old one had left. 



