28 The Ornithology of Chester County 
Philadelphia, may prove interesting in comparison 
with the valuable combination averages by Dr. Stone 
for the Delaware Valley Ornithological Club. 
I have been at some disadvantage in working 
alone, especially when unable to make frequent visits 
to the habitats of extremely local species, but on 
the other hand the percentage of error may possibly 
be less than where several observers of less experi- 
ence work a neighborhood. My experience in horizon 
and census work has taught me something of com- 
parative abundance and I believe my averages for 
bulk arrival and departure to be of greater value and 
more nearly correct than the averages of first arrival 
and last seen; especially taking in consideration the 
utter impossibility of always distinguishing the bona 
fide first arrival from the occasional holdover. 
Migration at Berwyn is seldom as well marked as 
in many other sections of the county; especially the 
vernal flight, when many of the smaller local land 
birds appear tardily via the Darby creek, and others 
pass in a northeasterly direction. “The visible au- 
tumnal movement is more direct and attended with 
greater numbers; the usual route southwesterly, the 
day fliers: Killdeer, Dove, Hawks, Blue Jay, Grack- 
les, Blackbirds, Swallows and Robin; the Canada 
Goose and Nighthawk, by day or night, and the 
Sandpiper by night. It is only occasional that a 
great movement is detected in the nightfliers, like 
that of September 24th, 1916, when the sky was 
partly overcast, the clouds thin and low, with mod- 
erate west wind; the air appeared alive with whis- 
pering voices of the small migrants at no great 
height, from dusk to late at night. 
a 
