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 How to Study Birds 91

could not fashion a Woodpecker’s dwelling; but a momentary comparison of the widely diﬂerent kinds of nests built by Swallows and Swifts (which, so far as nesting tools are concerned, may be classed with Swal» lows) readily shows how little the structure of the bird has to do with nest architecture.

By far the most important factor governing the character of a bird’s nest is the condition of its young at birth. Indeed, in considering this

SIMPLE NEST os KILLDEER. A PR/ECOCIAL KH‘LD (Meridian N. VuJune 7. tags)

question we are brought Very near to an attempt to determine the origin of birds’ nestst

In a rough classiﬁcation we may place birds in two groups: ﬁrst, those whose young leave the nest the day they are hatched; Second, those whose young are reared in the nest. Birds of the ﬁrst class are termed praecocial; those of the second. altricial. Compare the newly hatched young of a Grouse with those of a Robin, and we have two admirable examples of precocialism and altricialism.