192 
The Pa^mig of the Jylrds. 
migrate exclusively in the daytime, we 
so rarely see anything of them on the 
l)assage. Our Ipswich birds were all 
tree swallows, — white-breasted mar¬ 
tins, — and might fairly be supposed 
to have come together from a compara¬ 
tively limited extent of country. But 
beside tree swallows there are purple 
martins, barn swalloAvs, sand martins, 
cliff swallows, and chimney swifts, all 
of which breed to the nortliward of us 
in incalculable numbers. All of them 
go south between the middle of July 
and the first of October. But who in 
New England has ever seen any grand 
army of them actually on the wing ? 
Do they straggle along so loosely as to 
escape.particular notice? If so, what 
mean congregations like that in the 
Ipswich dunes? Or are their grand 
concerted flights taken at such an alti¬ 
tude as to be invisible ? 
On several afternoons of last Sep¬ 
tember, this time in an inland country, 
I observed what niiglit fairly be called 
a steady stream of tree swallows fly¬ 
ing south. Twice, while gazing up at 
the loose procession, I suddenly became 
aware of a close bunch of birds at a 
prodigious height, barely visible, cir¬ 
cling about in a way to put a count 
out of the question, but evidently some 
hundreds in number. On both occa¬ 
sions the flock vanished almost imme¬ 
diately, and, as I believed, by soar¬ 
ing out of sight. The second time I 
meant to assure myself upon tliis point, 
but my attention was distracted by 
the sudden appearance of several large 
hawks within the field of my glass, and 
when I looked again for the swallows 
they were nowhere to be seen. Were 
the stragglers which I liad for some 
time been watching, dying high, but 
well within easy ken, and these dense, 
hardly discernible clusters, — hirundine 
nebulae, as it were, — were all these 
but parts of one innumerable host, the 
main body of wliich was ])assing far 
above me, altogether unseen ? The con¬ 
jecture was one to gratify tlie imagi¬ 
[ August, 
nation. It pleased me even to tliink 
that it might be true. But it was 
only a conjecture, and meantime an¬ 
other question presented itself. 
When this daily procession had been 
noticed for two or three afternoons, it 
came to me as something remarkahle 
that I saw it always in the same place, 
or rather on the same north and south 
line, while no matter where else I 
Avalked, east or west, not a swallow 
was visible. Had I stumbled upon a 
regular route of swallow migration ? 
It looked so, surely; but I made little 
account of the matter till a month 
afterward, when, in exactly the same 
place, I observed robins and bluel)iids 
following the same course. The robins 
were seen October 26, in four docks, 
succeeding each other at intervals of 
a few minutes, and numbering in all 
about loO birds. They dew directly 
south, at a moderate height, and were 
almost certainly detachments of one 
body. The bluebird movement was 
two days later, at about the same hour, 
the morning being cold, with a little 
snow falling. This time, too, as it 
happened, the dock was in four detach¬ 
ments. Three of these were too com¬ 
pact to be counted as they passed; the 
fourth and largest one was in looser 
order, and contained a little more than 
a hundred individuals. In all, as well 
as I could guess, there might have been 
about three hundred birds. They kept 
a straight course southward, dying high, 
and with the usual calls, which, in au¬ 
tumn at least, always have to my ears 
a sound of farewell. Was it a mere 
coincidence that these swallows, blue¬ 
birds, and robins were all crossing the 
valley just at this point? 
This question, too, I count it safer to 
ask than to answer; but all observers, 
I am sure, must have remarked so much 
as this, — that birds, even on their 
migrations, are subject to strong local 
preferences. An ornithologist of the 
highest re])ute assures me that his own 
exj)erience has convinced him so strongly 
