INTRODUCTION. 11 
particularly rich in bird life, while some adjoining and similar region is 
almost devoid of it. Usually a little inquiry shows that the first region has 
been visited during the period of migration either in spring or fall, while the 
other has been seen only during midsummer or in winter. Any careful 
observer who has lived for years in a region outside the great bird highways 
must have noted the almost complete absence of certain species one year 
and their reappearance subsequently in normal or even in extraordinary 
numbers. We have not time here to discuss the causes of such variations, 
but we are doubtless safe in saying that each has a simple and satisfactory 
explanation, although this may not be the same in every case. The im- 
portant thing for us to note is that the facts on which estimates of bird 
population can be based are few and unsatisfactory and we are very likely 
to be misled and to reach conclusions which prove eventually far from the 
truth. In seeking to obtain an approximation to the truth in regard to 
increase or decrease dependence has been placed largely upon the writer’s 
personal experiences, in Michigan and elsewhere, but all sources of information 
which seem trustworthy and pertinent have been freely utilized. 
In certain cases there can be no question as to a great decrease in numbers 
in recent years. For example, the Passenger Pigeon and the Wild Turkey 
have become absolutely extinct, while the Sandhill Crane and the Northern 
Raven have dwindled from abundant species almost to the verge of extinction. 
On the other hand, it would seem, from recent records, that the Barn Owl, 
the Cardinal, Henslow’s Sparrow, Baird’s Sandpiper, and a few other species 
had increased decidedly in the last few decades. In the case of rare species, 
however, a very large element of error is likely to creep in. We must not 
forget that in such cases the number of birds taken or recorded will be directly 
proportional to the number of good observers in the field; and there can be 
no question that the number of such observers has increased very, largely 
in recent years. Hence we may fairly suppose that if a somewhat rare species 
—rare enough to be worthy of record whenever seen—were to remain prac- 
tically stationary as to abundance, it would nevertheless be reported much 
more frequently now than formerly, and unless on our guard we should be 
misled as to its actual numbers. On the other hand it seems highly probable 
that the Robin, for example, has largely increased in Michigan as the forests 
have been removed, the marshes drained, and cultivated fields, meadow 
land, pasture, and orchard have taken their place. This bird, however, 
being fairly common everywhere receives little attention in the bird journals, 
and the matter of its abundance is seldom discussed, unless as happens occa- 
sionally, it becomes a decided nuisance to the fruit grower. 
An instance of a different character is seen in the Red-winged Blackbird. 
The draining of immense areas has materially reduced the breeding grounds 
of this species, while at the same time the great increase in the cultivated 
areas surrounding the nesting places which are left has tended to distribute 
the harm done so that complaints of damage are now of comparatively 
infrequent occurrence. It seems reasonably safe to say that there has been 
a noticeable decrease in the numbers of this species, yet undoubtedly there 
are regions in which the harm done is as great now as at any previous time. 
In addition to the Passenger Pigeon and Wild Turkey," already exter- 
minated, there are at least eight other species which have decreased so 
noticeably during the last few decades as to be now on the verge of extinction 
at least in Michigan. These are the Greater Egret, the Sandhill Crane, the 
Knot, the Bartramian Sandpiper or Upland Plover, the Hudsonian Curlew, 
the Prairie Chicken, the Pileated_Woodpecker_and the Northern Raven. 
