Food and Water 181 



nection and they are often retained in the gizzard for considerable 

 lengths of time, as evidenced by their worn condition. 



In Smyth's records for October, the gizzards averaged thirty-four 

 particles of grit each which composed nine and three-tenths per 

 cent of the gizzard contents. The extremes ranged from several hav- 

 ing no grit at all to one having three hundred and ten bits of gravel 

 (thirty-two per cent of contents). Other highs were two hundred 

 and ninety-seven ( thirty-six per cent ) and one hundred and seventy- 

 seven (forty-five per cent) stones. Two having no stones contained 

 worn Crataegus seeds. 



In Smyth's November records, the gizzards averaged thirty-seven 

 bits of grit, which were nine and nine-tenths per cent of the con- 

 tents. Eleven had quartz stones and four had worn Crataegus seeds 

 but no gravel. His winter records showed an average of twenty- 

 seven stones each (seven and three-tenths per cent of gizzard con- 

 tents ) . In six spring records, the gizzards averaged fifty-eight stones 

 each, fourteen per cent of the total contents. 



Kuhn ( 1940 ) found gravel in only nine crops out of two hundred 

 and thirty examined, but he did not report on the gizzard contents. 

 This indicates the slow rate of ingestion of gravel needed to main- 

 tain the required quantity in the gizzard. Similarly, Nelson et al. 

 (1938) found only eight crops out of one hundred and eighty-four 

 to contain gravel, while of one hundred and seven gizzards from 

 the same specimens, seventy-six contained gravel averaging eight- 

 tenths cubic centimeters or one-third teaspoonful each. Of those 

 not containing gravel, all had hard seeds showing wear, including 

 those of rose, greenbrier, sumac, dogwood, witch hazel, and black 

 gum. 



Kelso's ( 1935 ) report gives the winter average of grit in the giz- 

 zards as seven and nine-tenths per cent in New York, ranging from 

 four and eight-tenths per cent in March to nine and eight-tenths 

 per cent in January. There is clearly a considerable variation in need 

 for grit at different times of the year, depending upon the nature of 

 the foods being eaten. Probably buds and twigs demand the most 

 grit while soft insects require the least. Hard seeds, if digested, also 

 would require a lot of grinding, while soft fruits would need little. 

 We can, therefore, generalize that grit is most needed in winter, 

 when hardest to get, and least required during the summer. 



