Burrill, Bird Migration. 
103 
reach their food supply so far as obtained from the water. The 
final breakup of the ice in spring must have indicated to the 
ducks that food supply could be found in open water spaces further 
North. If this be too anthropomorphic a supposition, can we not 
say that the local migration of ducks up and down the river for 
twenty-five miles (or probably much further than tne observer 
could locate and show by actual observation), would discover to 
the older ducks strips of open water Northward which had been 
frozen previous to the local migrations Southward? leaving 
this question open for those who have more leisure and special 
opportunity to observe these facts, I wish to turn to another illus¬ 
tration of local migration which seems to bear out the same point 
<pf view. 
On the way from Neenah to Oshkosh, Wisconsin, along the 
shores of Lake Winnebago, August 17, 1910, the thousands and 
thousands of midges observed along the way were especially 
remarkable. There was only one species so far as sight or col¬ 
lecting efforts could discover . ( Chironomus plumosus) , this 
species covering the trees, fences, mail boxes, ploughed ground, 
and even the dusty roadway. Some miles South from Neenah, 
many swallows were noticed coming Northward along the fields, 
slowly advancing and busily feeding in the fields and flying low 
over all the country as they normally do on cloudy days (further 
observations on this species of midge in particular will be pub¬ 
lished in Bull. Wis. Nat. Hist. Soc. Vol. 10, 1912). Three dif¬ 
ferent flocks of these swallows must have numbered into thousands 
each. Without other proof as to the presence of a large variety 
of insects, it seems quite reasonable to suppose that these birds 
were eating the midges everywhere abundant, undoubtedly gorg¬ 
ing their stomachs with the only adequate food supply visible. 
The flocks were chiefly white-bellied tree swallows ( Trachycineta 
bicolor (Vieill) ) one barn swallow, solitary ( Chelidon erythro- 
gaster (Bodd) ), and I thought I recognized one bank swallow 
(Riparia riparia (L.) ). Not necessarily in these flocks but appar¬ 
ently attracted in the same way was a kingfisher ( Ceryle alcyon 
(Linn.) ) and several sand pipers (perhaps Actitis). 
In the afternoon, further flocks of swallows and some black¬ 
birds ( Agelaius phoeniceus Linn) were seen. These birds were 
in rather more scattered flocks at this time of day and were also 
