Behavioural plasticity in the early breeding season of pelagic seabirds - a case study of thin-billed prions from two oceans

Table 5 Isotopic niche metrics of Thin-billed prions Pachyptila belcheri from the Falkland Islands and Kerguelen, calculated with the SIAR package in R (R Development Core Team 2014)

Symbol	Explanation	Falklands (blood)	Kerguelen (blood)	Falklands (feathers)	Kerguelen (feathers)
LOC	Location of centroid
	δ¹³C	−18.74	−23.30	−24.41	−23.14
	δ¹⁵N	12.26	8.90	8.25	8.58
SEA	Area of the standard ellipse (isotope niche width)	4.06	1.11	5.36	1.64
SEAc	as above, corrected for sample size	4.28	1.17	5.66	1.73
NR	trophic length (range in δ¹⁵N)	5.90	1.10	6.95	2.19
CR^a	diversity of basal resources (range in δ¹³C)	5.20	5.00	10.45	5.46
CD	niche width 2 (Mean distance to centroid)	1.79	0.81	1.50	1.17
MNND	mean Nearest Neighbour Distance	0.53	0.18	0.80	0.38

^aincluding the exceptions (birds with a temperate distribution) marked in Fig. 5
Feathers are grown during the moult period while blood cells represent the early breeding period. The location of the centroid (LOC) indicates where the niche is centered in isotope space. A Bayesian approach based on multivariate ellipse metrics was used to calculate the standard ellipse area SEA, which represents the core isotope niche width [35]. To describe the spread of the data points, parameters proposed by [34] were calculated. As proxies of intrapopulation trophic diversity, the mean distance to centroid (CD) and the mean nearest-neighbour distance (NND) are given. Information on the trophic length of the community is given as the δ15N range (NR), and an estimate of the diversity of basal resources is provided by the δ13C range (CR)

ISSN: 2051-3933