Nesting Success in Altricial Birds

NEARLY 20 years ago I presented a table in which it was shown that the percentage of success in 10 studies of open-nesting altricial birds averaged 43 for the eggs and 46 for the nests. I also pointed out that nesting success in hole-nesting altricial birds had been found to average about 66 per cent (1937: 143). This table on the opennesters has been referred to by many workers; it seems high time to bring the subject up to date. In Table 1, 35 studies are summarized on the success of altricial species that build open nests. Three of the papers in the 1937 table are omitted: Clabaugh (1926) because no information is given as to the species involved, Nice (1923) because most of this material is included in Nice (1931), and Walkinshaw (1936), since this study on 46 nests of the Field Sparrow is replaced by unpublished notes on 593 nests. The figures in Potter (1915) and Clabaugh (1925) have been altered by the omission of hole-nesting altricials and of precocial species. Because of the wealth of material a lower limit of 30 nests was set for this table. No nest is included unless at least one egg was laid in it; this rule necessitated recalculations with Howell's1942) and Kendeigh's (1942) papers. Twenty-eight of the studies were carried out in the United States, six in Great Britain, and one in Germany. Success of 7, 788 nests was 49 per cent. Hatching success of 21, 040 eggs was 60 per cent, while fledging success of 21, 951 eggs came to 46 per cent. The corresponding figures in 1937 were: success of 814 nests, 46 per cent; hatching success of 1, 994 eggs, 61 per cent; fledging success, 43 per cent. Now, with 10 times as many nests and eggs, the success of nests and fledging of eggs prove to be 3 per cent higher than before. The hatching success of eggs has dropped 1 per cent. The success of hole-nesting birds averages distinctly higher than that of open-nesters. Table 2, largely taken from Table 9 in Allen and Nice (1952), summarizes hatching and fledging success in 20 studies in the New World and 13 in the Old. I have not included Creutz's (1949) study of the Tree Sparrow (Passer montanus), where only 379 young were fledged from 855 eggs (44. 3 per cent), since the examination of the nests caused a considerable amount of desertion. Hatching success of 34, 000 eggs was 77 per cent; fledging success of 94, 400 eggs was 66 per cent. A further check on the validity of these figures may be obtained vsl 1957 * � � � � � a ᵢ � � � �