. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. 163 Reproductive Success Hatching success was (45 of 182 nests) in 1998, (74 of 261 nests) in 1999, and (4 of 17 nests) in 2000. Using those nests with definitively known lay dates, there was no seasonal change in hatching success in 1998 (logistic regression, n = 118 nests from 25 February to 4 June 1998: Wald X- = , df = 1, p = ). In 1999, there was also no significant seasonal change in hatching success (logistic regression, n = 231 nests from 7 February to 30 May 1999: Wald X- =
. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. 163 Reproductive Success Hatching success was (45 of 182 nests) in 1998, (74 of 261 nests) in 1999, and (4 of 17 nests) in 2000. Using those nests with definitively known lay dates, there was no seasonal change in hatching success in 1998 (logistic regression, n = 118 nests from 25 February to 4 June 1998: Wald X- = , df = 1, p = ). In 1999, there was also no significant seasonal change in hatching success (logistic regression, n = 231 nests from 7 February to 30 May 1999: Wald X- = , df = 1, p = ). Fledging success was (47 of 74 nestlings that hatched) in 1999; thus, overall reproductive success was (47 fledglings from 261 nests). Duration of Breeding Cycle and Breeding Frequency Across Years by Males and Females We recorded 373 feeding events to 1-year-olds in 1998 and 374 feedings to 1- year-olds in 1999. In January and February, during the early part of the breeding season, roughly one-third to one-half of feedings to 1-year-olds was made by males (Fig. 1). As the new breeding season progressed, however, male effort tapered off, such that nearly all feedings observed in April, May, and June were made by females. This clearly indicates a difference in the duration of parental effort by males and females, though it does not address whether their care for a 1-year-old nestling prohibits them from attempting to start a new nest that same Figure 1. Feedings to 1-year-old great frigatebird fledglings made by males and females on Tern Island in 1998 and 1999. Total sample size was 373 and 374 feeding observations in 1998 and 1999. respectively. Male plumage varied primarily in breast coloration, ranging from black to gray to brown. Based on five categories of breast coloration, we found that the males feeding 1-year-old offspring in 1999 were more likely to be brown than were males on new nests or males trying to attract a mate
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