Degree Name

Master of Science (MS)

Semester of Degree Completion

2001

Thesis Director

Eric K. Bollinger

Abstract

Renesting - Female's success after nesting failure. Many birds are unsuccessful in their first nesting attempt, so renesting is often a very important way for birds to increase their lifetime fitness and for populations to maintain stable numbers. I examined the importance of renesting and the factors that encourage or discourage a female from renesting and also the factors that affect the success of these renests. I also looked for patterns in renesting behavior (e.g., renesting interval, renesting distance, percentage of females that attempt renests, and the success of renests) of birds by comparing different studies. I used a total of 36 studies in the different analyses that had a sample size of at least 15 individually marked females to minimize the error of misidentification of females or nests. Of species that renest, the percentage of females that renested varied from 1.4% to 85%. The success of renesting also varied from 7.0% to 78.4% between species. Examination of 11 different studies did not uncover a statistically significant difference between the average first nest success of females (41.1%) and their renesting success (42.8%; t = 0.63, df= 10, P≥ 0.10). Although most species (52.9%) showed a decline in clutch size from first nest to renest there was not a statistically significant difference when comparing species that increased (n = 2), decreased (n = 9) or showed no change (n = 6) in clutch size (x2 = 4.17, df = 2, P≥ 0.10). Even with a decline in clutch size reported for over 50% of the studies, renesting provided some species over 25% of all young produced in a season. The percentage of females that will renest and their success rates are affected by the amount of time left for renesting in the breeding season. The latitude where a bird nests can influence the percentage of females that renest because of the shorter breeding season that is usually associated with an increase in latitude. Another factor affecting renesting percentage was the stage of the breeding process in which the nest was lost. Many females will renest if the clutch was lost during laying or early incubation but not after young have hatched. However, I found no statistically significant correlation between the length of the breeding season and the percentage of females that renest (n = 16, r = 0.27). The renesting interval (the length of time from loss of nest to the laying of the first egg in the next nest) also did not show a statistically significant correlation with the percentage of females that will renest (n = 17, r = 0.10), even though by having a shorter renesting interval a female can lengthen the amount of time left in the breeding season. The time involved in renesting can also be affected by the distance that a female travels to renest, but, again, there was no statistically significant correlation between the distance that a female traveled to renest and the percentage of females that renested (n = 11, r = 0.21). A factor that did affect the percentage of females that would renest was the availability of rich food sources. The lack of statistically significant correlations among species for many of the factors involved in renesting suggests the variability of many of these factors. That variability suggests that managers need to understand their particular area and how each particular species reacts to the different factors affecting renesting in order to better manage the area and species. There should also be more studies examining the effect of renesting on the life expectancy of females because, though renesting seems to be an important source of fitness, there has been little done to examine the long-term affect renesting has on the survival of a female.

Renesting of the Dickcissel at Prairie Ridge State Natural Area. Dickcissels (Spiza Americana) have been declining over the past 25 years. Possible reasons for this decline are loss of birds on their wintering grounds in Venezuela, where they are considered an agricultural pest and are persecuted; severe habitat loss (though most occurred before 1966) on their breeding grounds; and the high incidence of nest loss. Dickcissels are known to renest, but there have not been any formal studies conducted to determine if renesting may help ameliorate the high rate of nest loss. By banding females with unique color combinations and attaching transmitters, we attempted to follow females from the loss of their first nest to subsequent nests. We observed 48 females (26 with unique color bands and 19 with working transmitters) from May to August, in 1999 and 2000. Of the 26 females that were color banded, 18 were artificially depredated (6 in 1999, 12 in 2000), and 7 of those females were detected renesting within the study area (3 in 1999, 4 in 2000). Fifty percent of the females renested after loss of their second nest (n = 6). Nest success for the 10 renests was 13.8% [10.0% for second nests (n = 7) and 24.7% for third nests (n = 3)]. Renests had 3.0 fledglings/successful nest and provided 20.7% of all fledglings. Females had an average renesting interval (the time from nest loss to the laying of the first egg in the renest) of 10.3 days (range of 7-15 days). There was a negative correlation between the wing chord length of the female and the renesting interval (r = -0.69); thus, larger females appeared to have shorter renesting intervals. The females that renested moved an average of 294 m in 1999 and 84 m in 2000 (range from both years of 17-530 m). Of the 16 females that we did not detect renesting, 7 females were located by airplane after leaving the fields in which they had originally nested. The distances from the original nest to where these females were found ranged from 0.81 to 32.20 km. Although females moved away from their original nest site to renest, the females did not significantly change their nest placement when renesting [i.e., they chose the same type of nesting strata (e.g., forb, grass or woody), the same distance from an edge (e.g., road, forest or row-crop), the same height of the nest from the ground, and the same height of vegetation in which to place their nest]. Though the females did not seem to change nest placement, renests were successful and provided an important source of fitness for the 7 females that were found renesting and may have been important for the other females that we were unable to locate renesting. Nest success was 6.9% for those females that lost nests naturally but improved to 9.1% when females that renested after being artificially predated were included. However, even with renesting, females still produced only 0.67 fledglings/female, which would not be enough to maintain a stable population in the study area.

Download

Included in

Ornithology Commons

Share

COinS