Activity patterns and effect of ticks on growth and survival of tropical roseate tern nestlings

Roseate Tern (Sterna dougallii) Science Article 1


Patterns of abundance of the seabird tick Amblyomma loculosum and their effectson Roseate Tern (Sterna dougallii) nestling growth, fledging age, and survival are describedon Aride Island, Seychelles, in 1997-1999. Female ticks attached to nestlings from 4to 14 days (to engorge) whereas male ticks attached for 1-3 days. The linear growth rate ofbirds carrying female ticks (0.24 g/day) was significantly different from that of nonparasitizednestlings of the same age and similar (or even lower) hatching weight (4.07 g/day).Parasitized nestlings that fledged did so 5.2 days later than nonparasitized nestlings of similarage. Only 37.5% of the nestlings infested with female ticks fledged compared with 83.3%of the noninfested nestlings. During the successful 1998 breeding season, around 100 nestlingsdied from tick infestation (24.3% of the nestling deaths). Ticks appeared to acceleratenestling mortality during periods of food shortage. Despite an annual difference of twoweeks in the timing of breeding of the Roseate Terns between 1997 and 1998, adult ticksparasitized nestlings in July, with an infestation peak occurring between 8-12 July in bothyears. However, in 1997, nestlings were parasitized at a younger age, suggesting that ticks(nymph stage) must attach to Roseate Tern adults as soon as they make a nest scrape (usuallyin May). Ironically, the frequent breeding failures of the Roseate Terns will result in lowerinfestation levels in subsequent years, which will benefit the birds.

Jaime A. Ramos, John Bowler, Laura Davis, Sarah Venis, John Quinn, andCarole Middleton, The Auk 118(3):709-716, 2001

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