Local Decrease in Bluebirds 



By WELLS W. COOKE 



EARLY last summer, iiuiuiries bewail to come to the Biological Survey 

 asking what had become of the Bluebirds. Letters sent to a few corres- 

 pondents l)r()ught back such uniform reports of decreased numbers that 

 it was deemed advisalile to make an extended investigation. As a result of a 

 voluminous correspondence conducted among our migration observers, rejiorts 

 have been recei\ed from 1 1 5 localities, representing the United States east of 

 the Mississippi Ri\'er and also southern Canada. A few inquiries to observers 

 living west of the Mississipj)i, and to others in the Gulf States, made plain 

 the fact that no Bluebird destruction had occurred in these sections; while 

 two-thirds of the rej^lies from the Northwest, Michigan, Wisconsin, Minne- 

 sota and Manitoba indicated no appreciable decrease in the birds' abundance. 

 Reassuring returns came from nearly all the eastern United States south of 

 the Ohio and Potomac Rivers, but immediately to the northward and from 

 the valleys of these two rivers to southern Ontario and northern New England 

 lies the belt of country which seems to have suffered most severely. Just 

 three-fourths of the letters from this section announce a decrease of Bluebirds. 

 In most cases the statements are very strong. For example, "decided decrease," 

 "very few," "much less than usual," "have not seen one this year," etc. 

 Several of our correspondents have made careful estimates of the num- 

 bers still left, and how they compare with former years. Northern Ohio reports 

 are most discouraging; one says only one pair on the average for each i'lvc 

 miles of country road traveled; another sees not more than ten individuals in 

 some forty long tramps; and another only two birds in a two-hundred mile 

 motor ride. Several observers who have the excellent habit of recording every 

 bird seen are able to give exact statistics; the average of these is 61 per cent 

 decrease; a still larger number of re[)orts make an estimate of the decrease as 

 50 per cent, and this latter figure is probably not far from the truth. In other 

 words, one-half the Bluebirds of a region more than 200 miles north and south 

 and nearly a thousand miles east and west have failed to appear this year of i g 1 2. 

 Nearly all the rei)orts affirm that it is the breeding Bluebirds that are missing. 

 The general statement is that the birds came late, but then in such members as 

 not to be noticeable by their absence, but that since the close of migration 

 Bluebirds have been rare. 



How or where the destruction occurred is not even hinted at in the whole 

 mass of evidence. Several reports from the Gulf States say that Bluebirds were 

 unusually common last winter, and that the extreme cold did not extend far 

 enough south to do any damage to them in this part of the country. The sec- 

 tion of country from which the largest shortage is rei)orted is that just north 

 of the birds' regular winter home; and though some individuals are to be 

 found in mild winters throughout much of this region; yet, if all these had 



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