HATCHING, GROWTH, AND MORTALITY OF MAGNIFICENT FRIGATEBIRD CHICKS IN SOUTHERN BAJA-CALIFORNIA

We studied growth and development of chicks of the Magnificent Frigatebird (Fregata magnificens) in 1985, 1986, and 1988 at a colony on Isla Santa Margarita, Baja California Sur, Mexico. Hatching peaked at weeks 7, 12, 17.5, and 23.3 of the calendar year. Hatching frequencies around each peak were distributed normally. Growth was analyzed using Richards' model. Total length had the lowest growth rate and mass the highest. The asymptote for mass was reached before 150 days, as was the asymptote for culmen; the asymptotes for wing and wingspan were reached later. Chick mortality, recorded over a six-month period, was considered to be low (46%). During the same period there was 90% replacement and new occupation of nests, which resulted in temporal and spatial clustering of the clutches laid during the season.