Daily activity budgets reveal a quasi-flightless stage during non-breeding in Hawaiian albatrosses

Abstract

BackgroundAnimals adjust activity budgets as competing demands for limited time and energy shift across life history phases. For far-ranging migrants and especially pelagic seabirds, activity during breeding and migration are generally well studied but the “overwinter” phase of non-breeding has received less attention. Yet this is a critical time for recovery from breeding, plumage replacement and gaining energy stores for return migration and the next breeding attempt. We aimed to identify patterns in daily activity budgets (i.e. time in flight, floating on the water’s surface and active foraging) and associated spatial distributions during overwinter for the laysan Phoebastria immutabilis and black-footed P. nigripes albatrosses using state-space models and generalized additive mixed-effects models (GAMMs). We applied these models to time-series of positional and immersion-state data from small light- and conductivity-based data loggers.ResultsDuring overwinter, both species exhibited a consistent ‘quasi-flightless’ stage beginning c. 30 days after initiating migration and lasting c. 40 days, characterized by frequent long bouts of floating, very little sustained flight, and infrequent active foraging. Minimal daily movements were made within localized areas during this time; individual laysan albatross concentrated into the northwest corner of the Pacific while black-footed albatross spread widely across the North Pacific Ocean basin. Activity gradually shifted toward increased time in flight and active foraging, less time floating, and greater daily travel distances until colony return c. 155 days after initial departure.ConclusionsOur results demonstrate that these species make parallel adjustments to activity budgets at a daily time-scale within the overwinter phase of non-breeding despite different at-sea distributions and phenologies. The ‘quasi-flightless’ stage likely reflects compromised flight from active wing moult while the subsequent increase in activity may occur as priorities shift toward mass gain for breeding. The novel application of a GAMM-based approach used in this study offers the possibility of identifying population-level patterns in shifting activity budgets over extended periods while allowing for individual-level variation in the timing of events. The information gained can also help to elucidate the whereabouts of areas important at different times across life history phases for far-ranging migrants.

Ontogenetic changes in at-sea distributions of immature short-tailed albatrosses Phoebastria albatrus

“…At the same time, we observed shifts in habitat use towards regions favored by adults: shelf break and slope regions and a constriction of coreuse areas. After the first year, birds undergo flight feather molt; this energy expenditure and compromised flight performance could contribute to reduced core areas (Gutowsky et al 2014b). For short-tailed albatrosses, learning may constitute recognizing favorable foraging grounds, but perhaps more importantly, young birds may need to learn to recognize profitable foraging opportunities, and discern when to land, as taking off from the water's surface is energetically expensive for albatrosses (Shaffer et al 2001b).…”

Escaping the oligotrophic gyre? The year-round movements, foraging behaviour and habitat preferences of Murphy’s petrels

“…Energy requirements are probably lower, yet during this period they also moult flight feathers which is an energetically demanding process. Indeed, recent studies have documented a quasi-flightless period associated with moult in many procellariids (Gutowsky et al 2014, Cherel et al 2016. Although very little is known about feather moult in Murphy's petrels, gadfly petrels perform a simple descendent moult, replacing primary feathers sequentially over a period of 3 to 4 mo (Bridge 2006).…”

Individual-level Variation and Higher-level Interpretations of Space Use in Wide-ranging Species: An Albatross Case Study of Sampling Effects

“…Pre-breeding and eggs (PBE) encompasses the end of non-breeding, the return of birds to the colonies for courtship, and the transition into egg laying and incubation (15-Oct to 15-Dec). The timing of reproductive events were derived from Arata et al (2009) and Gutowsky et al (2014b) and typically varies little among colonies or between species (at most by c. 2 weeks). Each period avoids overlap with the equinoxes and intervals of most intensive logger deployment and recovery (15-Dec to 01-Jan).…”

“…All remaining locations were then processed using hierarchical state-space models (SSMs) estimated with Bayesian techniques (Jonsen et al, 2005;Block et al, 2011;Winship et al, 2012) to improve estimate accuracy and consistency across colonies and device types and to avoid unnecessary data loss (for SSM details see Gutowsky et al, 2014b). We divided daily locations into four periods of the annual cycle approximately overlapping different life history phases (phenology can vary between species and colonies by c. 1-2 weeks) for subsequent analyses (Figure 1).…”