Atlantic Loggerhead Nesting 77 



RESULTS AND DISCUSSION 



Nesting Activity 



The 1979 loggerhead nesting season at Cape Island encompassed 10 

 days, from the first clutch on 15 May to the last clutch on 28 August. 

 Results of 63 surveys of the Cape Island beach are depicted in Figures 1 

 and 2. Table 1 shows the estimated total numbers and the mean (± 

 standard deviation) numbers of nests and false crawls per week. Since 

 the surveys included almost 60% of the nesting season, we believe our 

 estimates reflect actual total nesting activity. 



Loggerheads on Cape Island laid 1,093 clutches in 1979 compared 

 to 1,451 clutches in 1978. This apparent 25% decline may have been 

 caused by rapid erosion of the beach and dune system, but past records 

 at CRN WR indicate considerable fluctuation in annual nesting activity 

 at Cape Island. Another possible explanation for variation in number of 

 nests per season is the two to three year breeding cycle of female logger- 

 heads. Kaufman (1975) and Davis and Whiting (1977) reported that 

 female loggerheads demonstrated a two year breeding cycle in Colum- 

 bia, South America, and Everglades National Park, Florida, respec- 

 tively. Davis and Whiting (1977) also found that the even-year breeding 

 population was about twice the size of the odd-year breeding popula- 

 tion, resulting in different levels of nesting activity each year. 



The frequency of false crawls or non-nesting emergences may be 

 related to quality of nesting habitat, since Davis and Whiting (1977) 

 observed more false crawls on poor quality beaches. Comparison of our 

 data with other studies supports this suggestion. In 1979, 71% of all 

 loggerhead emergences on the Cape Island beach were false crawls. The 

 mean number per night was 25.8 (SD = ± 22.21), compared to 5.3 per 

 night at Cape Island in 1939 (Caldwell 1959), a five-fold increase. Dif- 

 ferent data collecting methods between our study and Caldwell's proba- 

 bly account for part of the increase. Also, Talbert et al. (1980) found 

 that the frequency of false crawls at Kiawah Island, South Carolina, 

 ranged from 28.7% to 47.7%, with a mean of 40.5%, from 1972 to 1976. 

 Kiawah Island, approximately 83 km southwest of Cape Island, has 

 experienced much less erosion (Hayes et al. 1977). 



Even though the frequency of false crawls is high, Cape Island is 

 heavily used as a loggerhead nesting area. We found a mean of 136.6 

 nests/ km of beach in 1979 based on the total estimated number of nests. 

 Ehrhart (1979) reported 44.2 to 79.2 nests/ km of beach at the Kennedy 

 Space Center on the east coast of Florida, while Talbert et al. (1980) 

 found an average of 9.5 nests/ km for five nesting seasons at Kiawah 

 Island. The nesting concentration at Cape Island indicates the impor- 

 tance of this island as a loggerhead rookery. 



Figure 1 depicts the seasonal nesting activity of female loggerheads 

 at Cape Island in 1979. Numbers of nests per night increased rapidly 



