Individual consistency in migratory behaviour of a pelagic seabird

Abstract

23Many animals migrate between breeding and wintering areas; however, whether each 24 animal behaves consistently in space and time between consecutive years is less well 25 understood. Furthermore, previous breeding state (successful or failed) is often not 26 considered when attempting to understand consistent individual differences in 27 behaviour that are likely to impact upon the subsequent behaviour. Between 2006 and 28 2010, we used geolocators to track the migratory movements of a pelagic seabird, the 29 streaked shearwater Calonectris leucomelas, with individuals (N = 46) being followed 30 for two years or more, including 23 birds that had chicks in two seasons and 23 birds in 31 just one season. All individuals, except for one bird, migrated to the same broad 32 wintering areas, and their migratory route as well as the centre of wintering distribution 33 did not change in relation to the previous breeding outcomes. Migration schedules 34 (dates of departure from the breeding colony, southward and northward migrations, and 35 first return to the colony) did not differ significantly between years for individuals that 36 had chicks during both years, while failed individuals left the breeding colony and 37 appeared to start the southward migration at an earlier date than the previous successful 38 year. Nonetheless, the timing of the southward migration was consistent within 39 individuals, including both males and females, over successive years regardless of the 40 previous breeding outcome, and also the timing of first return back to the colony for 41 females that had chicks in the both previous years and eggs in the both following season. 42This may imply the existence of individual-specific broad time schedules, possibly a 43 circannual rhythm, though ecological conditions might affect the exact timing of the 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 3 actual departure event. Our results present evidence for high levels of individually 45 consistent behaviour for this pelagic seabird outside the breeding season. 46 47

Methods for detecting and quantifying individual specialisation in movement and foraging strategies of marine predators

“…As such, the data can be used to examine repeatability in foraging destinations (i.e. site fidelity), migration schedules (timing and duration of events), fidelity to wintering areas and routes, and consistency in habitat use or preference , Guilford et al 2011, Thiebot et al 2011, Baylis et al 2015a, Yamamoto et al 2014, Arthur et al 2015.…”

“…Therefore, in order to apply the methods listed above (correlations and repeatability analysis), spatial data are typically reduced via summary statistics to a single dimension, or are analysed separately (e.g. Phillips et al 2005, Dias et al 2013, Ceia et al 2014, Yamamoto et al 2014, Potier et al 2015. The most common summary data derived from each trip that have been used in this way include the total duration, total distance travelled (summed great circle distances between fixes), maximum range (great circle distance to the furthest location), and bearing at departure or to the furthest point (Hamer et al 2001, 2007, Soanes et al 2013, Ceia et al 2014, Patrick et al 2014, Baylis et al 2015b, Oppel et al 2015, Potier et al 2015.…”

“…The most common summary data derived from each trip that have been used in this way include the total duration, total distance travelled (summed great circle distances between fixes), maximum range (great circle distance to the furthest location), and bearing at departure or to the furthest point (Hamer et al 2001, 2007, Soanes et al 2013, Ceia et al 2014, Patrick et al 2014, Baylis et al 2015b, Oppel et al 2015, Potier et al 2015. For the non-breeding season, the analyses are often of migration schedules (timing and duration of events; Croxall et al 2005, Dias et al 2011, Yamamoto et al 2014, or the total distance travelled during the migration (Muller et al 2014). Other 1-dimensional data used in studies of individual specialisation include dive characteristics and activity metrics (Laidre et al 2002, Staniland et al 2004, Cook et al 2006, Ratcliffe et al 2013, Patrick et al 2014, Potier et al 2015, Wakefield et al 2015.…”

“…It is possible to study individual specialisation in space, and not only in trip characteristics, based on distances between the centroid of the locations at 2 different times for the same individuals tracked during the breeding season (Navarro & González-Solís 2009, Ceia et al 2014, or between centroids in different winters (Dias et al 2011, McFarlane Tranquilla et al 2014, Yamamoto et al 2014, Lea et al 2015. Distances can also be calculated between pairs of migratory routes (e.g.…”

“…Individual specialisation and behavioural consistency are known to be widespread across a range of taxa and behaviours; they have been demonstrated for a number of species of marine predators in foraging behaviour, migratory routes, dive characteristics, diet, timing of events, activity patterns and habitat choice, and foraging site fidelity during breeding and non-breeding periods (Hoelzel et al 1989, Staniland et al 2004, Sargeant et al 2005, Guilford et al 2011, Thiebot et al 2011, Patrick et al 2014, Yamamoto et al 2014, Wakefield et al 2015. Because marine predators forage on highly patchy and more or less predictable food resources at the coarse-to meso-scale (tens to hundreds of kilometres) and over days and weeks, the incidence of specialisation is unsurprising (Weimerskirch 2007, Wakefield et al 2015.…”