. The Canadian field-naturalist. 402 The Canadian Field-Naturalist Vol. 88. -ST^N -56 N ss'n -54-N ST^W Figure 3. The regional distribution of the total numbers of breeding areas (below the slashes) and successful breeding areas, in July 1969. The regions have a dimension of 1/2 degree latitude by 1 degree longitude. Productivity In 1968, 64% of 129 breeding areas were successful compared to 56% of 245 in 1969. The differences between 1968 and 1969 are not statis- tically significant. We found young per nest with young in July 1968, and young per nest with young in July 1969. E
. The Canadian field-naturalist. 402 The Canadian Field-Naturalist Vol. 88. -ST^N -56 N ss'n -54-N ST^W Figure 3. The regional distribution of the total numbers of breeding areas (below the slashes) and successful breeding areas, in July 1969. The regions have a dimension of 1/2 degree latitude by 1 degree longitude. Productivity In 1968, 64% of 129 breeding areas were successful compared to 56% of 245 in 1969. The differences between 1968 and 1969 are not statis- tically significant. We found young per nest with young in July 1968, and young per nest with young in July 1969. Eighty-three to eighty-six percent (53-55 of 64) of breeding areas examined in May 1969 were occupied. The uncertainty is due to two empty nests with only one adult nearby. Thirty-six (65-68%) of these nests contained young 6-10 weeks old in July. There were young produced per occupied breeding area. The dis- tribution of the number of young per nest with young is given in Figure 5. Nest Failures Eleven (22%) of the 51 nests active in May were standing but empty in July, and four were gone. The causes of the failures are unknown, but two further observations are suggestive. First, the usual reaction of the incubating adult as we flew by the nests in May was to sit tight on the eggs. In seven cases the incubating adult stood up or flew from the nest; of these, one was gone, four had failed, and only two were still active by July. The difference between this group of nests and the remainder of those seen in May is significant with X^ = , 1 df, andP< Second, there was a statistically significant tendancy for breeding areas empty in July 1968 and active in May 1969 to fail before July (Table 3, x' = , 1 df, P < ). Table 3 — Status, in July 1969, of those breeding areas visited in 1968 and active in May 1969 Status in July 1969 Empty Active Empty in 1968 Active in 1968 6(60%) 3(14%) 4(40%) 18(86%) Population Age Structure Sixteen (16%) of 101 Bald E
Size: 1818px × 1375px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorottawafieldnaturalistsclub, bookcentury1900, bookcolle
