Juvenile survival in a tropical population of roseate terns: interannual variation and effect of tick parasitism

Abstract

Many demographic studies on long-lived seabirds have focused on the estimation of adult survival, but much less is known about survival during the early years of life, especially in tropical species. We report analyses of a capture-recapture dataset of 685 roseate terns ringed as fledglings and adults between 1998 and 2005 on Aride Island, Seychelles, and recaptured/resighted at the same colony site over a 5 yr (2002 to 2006) period. A multistate model was used to estimate survival for different age classes, including juvenile (first-year) birds returning as non-breeding prospectors. The effect of infestation by parasites (ticks) on survival was also examined. Overall, the estimated return of first-year individuals to the natal colony was very variable, ranging from 2 to 22%. Conditioned on survival, the probability of returning from Age 2 yr onwards increased to 70%. Survival rates were best modeled as time-specific, with estimates varying from 0.02 to 1.00 (mean 0.69) in firstyear birds with a marked negative effect of tick infestation. In older birds (minimum age of 2 yr), the annual estimates fell between 0.69 and 0.86 (mean 0.77). Using a components of variance approach for estimation of year-to-year variation, we found high temporal variability for first-year individuals (coefficient of variation [CV] = 65%) compared to much less variation in the survival rate of older birds (CV = 9%). These findings agree with the life-history prediction that demographic rates of juveniles are usually lower and more variable than those of older individuals. Our results are also consistent with the predicted negative effect of tick parasitism on juvenile survival. Compared with data from other roseate tern populations, survival over the first 2 yr (Age 0 to 2 yr) was 18 to 40% higher in this study, suggesting that a high 'young' survival rate may be an important demographic trait in this tropical population to compensate for the low annual reproductive success. Our data show that estimating survival of young individuals may be crucial to elucidating the demographic tactics of seabirds.KEY WORDS: Ectoparasitism · First-year survival · Multistate capture-recapture models · Temporal variability · Sterna dougallii Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 365: [277][278][279][280][281][282][283][284][285][286][287] 2008 that of adults and shows high temporal variation when compared to survival of subsequent age classes (Francis & Saurola 2004, Harris et al. 2007), a pattern also found in mammals (Gaillard et al. 1998(Gaillard et al. , 2000 and turtles (Chaloupka & Limpus 2005). In seabirds, fecundity is the demographic trait most affected by variations in environmental conditions, and adult survival is normally high and stable (Nisbet & Cam 2002) although changes in food availability (Oro & Furness 2002) and large-scale climatic and weather events (e.g. North Pacific Index [NPI], Jones et al. 2002; hurricanes, Spendelow et al. 2002) are known to induce some ...

Laying date, body mass and tick infestation of nestling tropical Roseate Terns Sterna dougallii predict fledging success, first‐year survival and age at first return to the natal colony

“…The present modelling replaces previous post‐fledging survival estimates for tropical Roseate Terns (Monticelli et al . ), as we added up to three additional years of recapture. Our modelling approach is based on multistate models developed by Spendelow et al .…”

“…Following Monticelli et al . (), survival parameters for older ages were always modelled as constant (notation ‘.’).…”

Adult and pre-breeding survival estimates of the Whiskered Tern Chlidonias hybrida breeding in southern Poland

“…Spendelow et al 2002;Lebreton et al 2003, Monticelli et al 2008b, Braby et al 2011Feare and Doherty 2011;Braby et al 2012). The data presented here are the first estimates of survival for this species.…”

“…Capture-recapture modelling Multistate (multistrata) models with an unobservable state (Pradel and Lebreton 1999;Spendelow et al 2002;Lebreton et al 2003;Monticelli et al 2008b) were used to account for the delayed maturation of young Whiskered Terns. Most young birds stay at their winter quarters during their first summer (2nd calendar year), similar to many other tern species (Cramp 1985;Gochfeld and Burger 1996); observations of 2nd year Whiskered Terns in European breeding colonies are scarce (but see Mees 1977;Cramp 1985;Latraube et al 2006; see also Results).…”

“…Each bird population has a specific pattern of age-and/or sex-related survival that may further depend on multiple factors: year, weather conditions, place of birth, parasite and predatory pressures, food supply, individual condition and individual heterogeneity (Nichols et al 1990;Spendelow et al 1995Spendelow et al , 2002Lebreton et al 2003;Monticelli et al 2008b;Braasch et al 2009;Monticelli and Ramos 2012). Demographic data of long-lived birds with delayed maturity show that survival probability differs between age-classes.…”