Page 8 - Soldatini2014

Local and Global Climate Effects on Storm Petrel Demography

Table 8. Percentage of variance expressed by each principal geolocators or satellite tracking devices are not small enough to be
component factor of the PCAs performed (Alboran Sea, used on this species. The trends of sea surface temperature and
Balearic Sea, Sicilian Channel, Adriatic Sea, and Aegean Sea: Al, chlorophyll [39] (figure S4a) may influence storm petrel survival.
L, S, Ad, Ae, respectively; sea surface temperature: SST and In particular, the conditions in the Alboran Sea zone resulted to be
chlorophyll: CHL). influencing adult survival. Considering sea surface temperature
and chlorophyll concentration effects separately, we observed that
ext cov % cov SST has a stronger direct effect while the CHL direct effect is
weaker (Table 9). It is still unknown what the Mediterranean storm
LsstPC1 70.069 petrel feeds on during winter. Our results suggest that they
LchlPC1 44.937 probably feed mainly on small fishes, not directly affected by CHL,
LchlPC2 29.623 as during the breeding period [27], and not on zooplankton that
AlsstPC1 82.34 would be directly affected by CHL concentration. Sea conditions
AlchlPC1 86.231 may induce birds to skip reproduction in years with high surface
AdsstPC1 87.756 temperatures and low chlorophyll levels at wintering sites, resulting
AdchlPC1 51.557 in lower encounter rates during the subsequent breeding season.
AdchlPC2 29.163 This would explain the drops in encounter rate observed in
SsstPC1 88.377 breeding seasons after high sea surface temperature and low
SchlPC1 78.176 chlorophyll concentration in winter conditions (figure S4a and b).
AesstPC1 88.872 Our results highlighted the relationship between environmental
AechlPC1 92.015 covariates and encounter rates, as also found in the Pacific and
other studies on impacts of climate change on avian populations
doi:10.1371/journal.pone.0094526.t008 [11,54].

will not have a negative effect on juvenile survival rate of the Finally with respect to predicted features of climate change [51],
Mediterranean subspecies. as we observed that colony region conditions affect chick and adult
survival, whereas conditions in the wintering areas affected adult
Adult survival was directly affected by the climatic conditions at survival, we can conclude that the stability of the Alboran sea
the time of breeding due to the adult’s needs to meet its own surface temperature due to anticyclonic systems [55] may result in
energetic requirements as well as those of the chick. Males tend to continuous upwelling in the area thus resulting in stability of
recruit earlier than females and recruitment was reduced in years survival of adult storm petrels during winter while the anticipated
with adverse prebreeding conditions, suggesting that younger birds decrease in precipitation and warmer summers [20] will positively
decided to delay recruitment to wait for better condition or more affect chick survival. Although we did not consider climatic effects
productive years. Carryover effects for the winter might occur as a on the food chain our result suggest future demographic stability
consequence [52]. It is noteworthy the fact that males of and an improvement of the species status. Further research on
Mediterranean storm petrels are smaller than females [53] and climate change effects on the food chain and consequent effects on
consequently adults may rear the chicks with fewer energy the Mediterranean storm petrel are currently missing and would
expenditure. help to forecast the species future conditions.

Identification of wintering-area Supporting Information
The original aspect of our study is the use of statistical models to
Figure S1 Colony and meteorological stations location.
identify seabird wintering areas, as illustrated for the storm petrel, (TIF)
a species difficult to follow at sea due to lack of technology, as
Figure S2 Correlation graphs for principal component
analysis (PCA) for building integrative climatic indices.
a) PCA of West Sicily rainfall data; b) PCA of the pre-breeding

Table 9. Model selection results.

Model Deviance NP AIC DAIC AIC weight

time eff 4125.67 24 4173.67 0.00 0.664
Al sst chl 4145.01 15 4175.04 1.37 0.335
Al sst 4145.01 15 4175.04 1.37 0.335
Al chl 4156.74 15 4183.76 10.09 0.001
L sst chl 4155.86 15 4185.86 12.19 0.001
Ad sst chl 4161.70 15 4191.70 18.03 0.000
Ae sst chl 4167.40 15 4197.40 23.73 0.000
S sst chl 4170.41 15 4200.41 26.74 0.000
Constant 4175.93 14 4203.93 30.26 0.000

Environmental, ‘‘time’’, and constant effects ‘‘i’’ were considered on survival, W, with climatic covariates in 5 areas of the Mediterranean (Al: Alboran, L: Balearic, Ad:
Adriatic, Ae: Aegean, S: Sicilian Sea). Deviance (Deviance), number of parameters (NP), DAIC and AIC weight are reported.
doi:10.1371/journal.pone.0094526.t009

PLOS ONE | www.plosone.org 8 April 2014 | Volume 9 | Issue 4 | e94526