Page 5 - Jakubas_et_al._2014_Storm_Petrels

74 D. Jakubas et al.

Table 1. Location of the compared European Storm Petrel colonies, sample size of wing length (WL) and body mass (BM) and
source of data. Regions: ME — Mediterranean, SA — South Atlantic, NA — North Atlantic. – — lack of data, ? — lack of informa-
tion about sample size. * — site where individuals of H. p. pelagicus were captured during migration.

Colony Site Location Region WL (n) BM (n) Source
Italy
Subspecies H. p. melitensis Marettimo Is., Albores-Barajas et al.
AEG Aegadian Is (2010)
Lalanne et al. (2001)
ME 46 –
Castro et al. (2013)
COR Corse France ME ? ? Medeiros et al. (2012)
Subspecies H. p. pelagicus
El Hierro Is. Canaries SA 79 79 Lalanne et al. (2001)
CAN SW Atlantic coast Portugal – 936 934 James (1983)
POR* Biarritz, Scott (1970)
BIS the Biscay Bay France SA 19 19 Evans (1977)
Skomer Is. Wales Evans (1977)
WAL1 Skokholm Wales NA 46 – Evans (1977)
WAL2 Puffin Island Ireland Furness & Baillie (1981)
IRL1 Inishvickillaun Ireland NA 6681 5589 Furness & Baillie (1981)
IRL2 Inishnabro Ireland Fowler et al. (1986)
IRL3 Hirta, St. Kilda Scotland NA 287 277 Furness & Baillie (1981)
SCO1 North Rona Scotland this study
SCO2 Yell Shetland NA 336 2275 Nygård & Einvik (1991)
SHE1 Foula Shetland Nygård & Einvik (1991)
SHE2 Nólsoy Faeroes NA 163 163
FAR Heimøya Norway
HEI Røst Norway NA 827 827
RØS
NA 125 77

NA 49 –

NA 108 108

NA 156 156

NA 34 34

NA 231 235

(ME — Mediterranean including Mediterranean length (n = 6), tarsus length (n = 5), tail length
colonies of the bigger subspecies H. p. melitensis; (n = 4) and bill length (n = 4). To test whether
and two groups of the smaller subspecies H. p. there is a relationship between morphometrics
pelagicus: SA — South Atlantic including the south- and SSD values (including POR) and between
ernmost colonies, NA — North Atlantic including morphometrics, SSD and latitude/longitude (ex-
the northernmost colonies) (Fig. 2, Table 1) differing cluding POR), we used the Spearman rank corre-
in environmental conditions (Appendix 1). We lation coefficient.
investigated relationships between morphomet-
rics and environmental conditions in three scales: Discriminant function for sex determination.
1) species scale including all colonies, 2) sub-
species scale including the colonies of the Atlantic To determine the sex of adult European Storm
subspecies H. p. pelagicus (SA and NA combined); Petrels, we used a discriminant function (DFA)
3) regional North Atlantic scale — including only based on structural biometrics of birds captured in
colonies situated in the North Atlantic (NA). the Faeroes. To find the best measurements for sex
identification, we did not use the stepwise
Sexual size dimorphism. To investigate sexual method as several authors strongly recommend
size dimorphism (SSD) in the European Storm avoiding this procedure (reviewed in Dechaume-
Petrel, we used data collected in six different loca- Moncharmont et al. 2011). Instead, we selected
tions, from individuals breeding in five colonies the DFA with highest effectiveness among various
(CAN, AEG, WAL1, SHE 1 and FAR; abbreviations functions with manually selected variables. We
— see Table 1) and caught on the Atlantic coast in assessed the effectiveness of the DFA, first by
Portugal (POR) during migration (originating examining the proportion of molecularly sexed
from the Atlantic population; Medeiros et al. 2012). individuals that were classified correctly using all
individuals in the analysis (self-test), and second
We measured SSD using the following formu- by cross-validation (each case is classified by the
la: SSD = [(m-f)/(m)]*100, where m and f is the functions derived from all cases other than that
mean value of specific morphological traits in case). Due to unequal sample size for males and
males and females, respectively (Smith 1999). females, we used a chance-corrected procedure
(Cohen’s kappa statistic) to determine if the classi-
We performed analyses only for variables for fication was better than random or chance alone
which we have data for > 3 locations, i.e. for wing