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Local and Global Climate Effects on Storm Petrel Demography

Table 6. Selection of the full recruitment (f.r.) age and test of time effect on survival and sex effect on recruitment age, only best
models are presented.

Model Deviance NP AIC DAIC AIC weight

Wt Ysex 3002.59 52 3106.59 0.00 0.827
Wt Y 3011.83 49 3109.83 3.24 0.164
Wt Y f.r. year fixed to 3 3019.74 48 3115.74 9.15 0.008
f.r. year 3 (age 2) 3128.14 24 3176.14 0.00 0.342
f.r. year 4 (age 3) 3127.74 25 3177.74 1.60 0.154
f.r. year 5 (age 4) 3127.74 26 3179.74 3.60 0.165
f.r. year 2 (age 1) 3134.77 23 3180.77 4.63 0.034

Deviance (Deviance), number of parameters (NP) and AIC [47] are reported. Preferred models are in bold.
doi:10.1371/journal.pone.0094526.t006

ettimo colony study conditions and structure are different from the Mediterranean [32]. It is possible that this result is due to the
most of known colonies, being the colony placed in a big and effects of environmental conditions on survival.
completely dark cave accessible only from the sea (thus predator-
free), and with a large number of accessible nests. The colony Effects of environmental conditions on demographic
characteristics make it very different from other monitored traits
Mediterranean colonies such as Filfla, Malta, where nests are
scattered in single inaccessible burrows in the rocks [24], and Survival exhibited two troughs (figure S3b), which might be due
Benidorm, Spain, where the colony is small (ca 300 nests) and in to factors related to colony dynamics (internal) and to environ-
two caves easily accessible for predators [49]. The database we mental factors (external). The influence of climate on demography
used in this study is based on a more complete and longer time is represented by the finding that the colony region’s climatic
series (21 years with one missing year vs 15 years with two missing conditions affect the recruitment age and survival of chicks and
years) than that used previously for the same colony in a adults. In particular, chick survival was affected by breeding-
comparative study [32]. This allowed us to investigate and period conditions and rainfall. Abundant rainfall before and cold
describe cues of the subspecies life history, thanks to predators weather during the chick-rearing period resulted in higher chick
absence, making it possible to infer about chicks natural mortality, mortality, as observed in 2010. These conditions may have
and the long time series allowing correlational analyses with produced wet conditions in the colony caves and reduced
climatic conditions trends. The population studied showed that the thermoregulation capabilities, inducing higher metabolic costs
pre-recruitment period may be shortened by unfavourable for chicks and parents [18]. In fact, in 2010, a year with higher
environmental and climatic conditions that may have lead to rainfall and lower temperature, we observed exceptionally high
earlier maturation as a consequence of lower adult survival (figure chick mortality in the field (only 20 fledged in the surveyed area of
S3b). Long-lived birds invest more in survival than fertility [50]. the colony), while we usually don’t find dead chicks when visiting
However, this study found that storm petrel tend to recruit earlier the colony. In the view of our results warmer summers and lower
in this colony compared to other monitored colonies throughout rainfall predicted as a consequence of the changing climate [51]

Table 7. Model selection results, only best models are presented.

Model Deviance NP AIC DAIC AIC weight

WB1+B2+t+WSR YPB1+PB2+sex 2984.08 55 3094.08 0.00 0.842
WB1+B2+t YPB1+PB1+sex 2989.76 54 3097.76 3.68 0.134
WB1+B2+t YPB1+PB2 2999.35 51 3101.35 7.27 0.022
Wt Ysex 3002.59 52 3106.59 12.51 0.001
Wt Yi 3011.83 49 3109.83 15.75 0.000
WB1+B2 Yi 3104.72 29 3162.72 68.64 0.000
Wi YPB1+PB2 3112.46 30 3172.46 78.38 0.000
Wi Ysex 3112.68 32 3176.68 82.60 0.000
WPB1+PB2 Yi 3121.82 28 3177.82 83.74 0.000
WWSR Yi 3124.11 27 3178.11 84.03 0.000
WWNAO Yi 3126.47 27 3180.47 86.39 0.000
Wi Yi 3127.74 29 3185.74 91.66 0.000

Climatic (PB: Pre-Breeding, B: Breeding, WSR: rainfall, WNAO: winter NAO), ‘‘time’’, and constant effects ‘‘i’’ were considered on survival, W, Yskipping the transition
probability from state pre-breeder to breeder, Y (‘‘+’’ denotes additivity). Deviance (Deviance), number of parameters (NP), DAIC and AIC weight are reported.
doi:10.1371/journal.pone.0094526.t007

PLOS ONE | www.plosone.org 7 April 2014 | Volume 9 | Issue 4 | e94526