REPORT ON BIRD CENSUSES, 1916-1920. 



29 



species of warblers, mockingbird, catbird, brown thrasher, 4 species 

 of wrens, and 5 species of thrushes. It will be noted that a large 

 number of these birds are insectivorous and that comparatively 

 few of them winter within the United States. 



The numerical decreases of some species on the above-mentioned 

 reports may be of interest. The figures given in Table 10 seem 

 small, but when it is considered that the total acreage to which they 

 apply is only an infinitesimal part of the whole area presented, they 

 become significant. 



Table 10. — Species of birds that in 1918 showed a marked decrease in numbers. 



Species. 



Number 



of 

 reports. 



Decrease 

 in pairs. 



Species. 



Number 



of 

 reports. 



Decrease 

 in pairs. 



Mourning dove 



6 

 8 

 9 



7 

 7 

 6 

 9 



11 

 11 

 13 

 17 

 11 

 7 

 30 



Scarlet tanager 



5 



8 



10 



Flicker 



Red-eyed vireo 



11 



Phoebe 



Marvland yellowthroat 



6 8 





Catbird 11 14 





Brown thrasher 6 8 



Baltimore oriole 



House wren 7 9 





Robin 











The greatest decrease in the total number of breeding pairs on a 

 given area was 46 § per cent on 40 acres at Florence, Ala., and two 

 other tracts showed decreases of over 40 per cent each. 



Examination of the reports shows that of the total land surveyed 

 only 6 acres more were plowed than in the preceding year, thus 

 eliminating the possibility that more intensive cultivation had caused 

 the birds to nest elsewhere. Neither could severe weather conditions 

 during the previous winter have affected those species that winter 

 south of the United States. 



E. H.Forbush, State ornithologist of Massachusetts, made an ex- 

 tensive investigation in 1917 of the effect on insectivorous birds of 

 the cold and rainy weather of May and June of that year. He found 

 that during that time thousands of birds perished from lack of food, 

 due to the weather conditions. Concerning this destruction of bird 

 life by the elements, he says in part: 5 



* * * The weather report asserts that the low temperature and lack of sunshine 

 retarded vegetation, so that the season at the close of May was from three to four weeks 

 later than normal. 



* * * It was not until the middle of June that the wild flowers appeared as they 

 ordinarily do in the latter part of May. There was a similar delay in the appearance 

 of insects. Eggs of insects failed to hatch at their usual time, but apparently the cold 

 weather did not destroy ttiem. With the exception of tent caterpillars and a few 

 others, insects appeared in their full, normal numbers later in the season. A few 

 birds appeared earlier than normally, but the main flight of insect-eating birds came a 

 week or ten days later than usual. Even then the birds came too soon, for their insect 

 food was not ready for them. Many of the early swallows and martins apparently suc- 

 cumbed to the cold storms which came after the birds arrived. Several ol servers 

 report finding dead martins and swallows in nesting boxes. * * * 



* * * In going over the reports from various correspondents tbe lirst fact almost 

 universally observed was that of an unusual flight of birds, particularly insc< t-eating 

 species, such as warblers. Only a very few observers had not noticed this. The next 

 fact noted was that the birds were much less shy than usual, and that they were seen 

 more about houses, in villages and closer to the ground than in ordinary seasons. 

 The warblers were so weak and so preoccupied in seeking food that many of them 

 could almost be taken by hand, and as they grew weaker some were so caught. 



• Forbush, E. H., Tenth Annual Report of the State Ornithologist, pp, 14-22, Boston. Mass., 1917. 



