Barn Owl Growth and Behaviorisms

BY GAYLI• PICKWI•LL Pl•te 11 TH• first Barn Owl (Tyro alba pratincola) the author ever saw was one that was shot by a neighbor in eastern Nebraska, and the author at the time, at the height of his taxidermy urge, was asked to mount it.He did mount it and for many years it was maintained proudly on its pedestal in the living room of the neighbor.In central California in the region of San Jose the author was later to learn that Barn Owls are common.At night in all California cities the peculiar scream of the Barn Owl, as it flies here and there after nightfall from its daytime retreat, is one of the most frequent and certainly most eerie of night sounds.This sound has been heard in most large cities of the Far West.The species nests in many localities.A significant crevice, even in a dirt bank made by the construction of highways, often suffices.In the region of San Jose, California, the bird frequently uses cavities in the immense live oaks (Quercus agrifolia).Two such nests have been recorded.Others have been reported in lofts of barns.One of the most surprising was a nest made in an inexplicable cavity on the side of a large stack of hay about nine miles from Los Banos in the San Joaquin Valley.This nest was discovered on May 29, 1929.On San Jose State College campus, these owls nested habitually in the casements below the windows of a high campus tower, and janitors told the author that these casements had been used as nest sites for many years.As later records will show, the Barn Owl is one of the most effective catchers of pocket gophers (Thomomys).Its method of hunting is described in my notes made on April 30, 1931:" . . .Two or three Barn Owls were seen hunting over the hay meadows in the region of Evergreen in the dusk.They flew back and forth, 'stood' about 30-40 feet in the air--and dropped precipitously."The parent owl often persists in sitting near her young and will not leave them, even when disfurbed.Such a record was made on April 30, 1931, at Evergreen California, and much later (May 6, 1939) a parent owl allowed herself to be photographed in rampant pose with her six young in a south casement of the college tower.On May 16 it was noted that, of the several young in this nest, the largest was fully twice the size of the smallest.This observation was made also of the young of the nest which was critically followed.ve1.a ]1948 PICKWELL, Barn Owl Growth and Behaviorisms PI½I•V/I•I•I•, Barn Owl Growth and Behaviorisms •u• k One of the nests of the college tower was followed carefully in 1928 throughout the full life history of the resultant young.The nest in the westernmost of these casements (a casement which measured 28" by 8 • inside, with a depth of 3' 8") had seven eggs on February 25.These were of the usual owl-egg coloring--dead white and strikingly oval in shape.One of the seven eggs hatched on March 12.The following record was made at the time: ". . .One owl hatched, egg shells by side of nest, six eggs yet Young very weak and helpless.Could not raise head.Said 'peep' however.Female (?) went off reluctantly--alighted on box and then away to same tree west.Two photos of nest.While at work, owl came in, alighted on side of building, and away again.No notes."Another young did not hatch until March 19, seven days later; and on March 21 a third hatched.On March 22, the fourth egg was pipped and the young was squeaking inside, and on March 23 this fourth hatched.Since these young owls were weighed carefully every day, it was learned that this fourth chick at hatching was appreciably less in weight than the egg from which it emerged.The egg had weighed 21.7 grams and the young owl weighed 17.9 grams.Since this newly hatched young had had no opportunity to eat, this lessening could be easily explained by the loss of the weight of the egg shell and the drying that accompanies hatching.On March 24, the following day, another egg with a young owl peeping inside weighed 21.8 grams.This egg hatched on March 25; the chick weighed 21.2 grams.This newly hatched bird squeaked as loudly as those hatched earlier.On March 27 the records state the following with regard to the ' sixth owl:" . . .Weight 18.5 grams.This one could not be measured for it was just out of the shell and had not straightened out as yet."The seventh Barn Owl egg apparently was addled, for it produced no young.