Carry‐over effects on the annual cycle of a migratory seabird: an experimental study

Abstract

Summary Long‐lived migratory animals must balance the cost of current reproduction with their own condition ahead of a challenging migration and future reproduction. In these species, carry‐over effects, which occur when events in one season affect the outcome of the subsequent season, may be particularly exacerbated. However, how carry‐over effects influence future breeding outcomes and whether (and how) they also affect behaviour during migration and wintering is unclear.Here we investigate carry‐over effects induced by a controlled, bidirectional manipulation of the duration of reproductive effort on the migratory, wintering and subsequent breeding behaviour of a long‐lived migratory seabird, the Manx shearwater Puffinus puffinus. By cross‐fostering chicks of different age between nests, we successfully prolonged or shortened by ∼25% the chick‐rearing period of 42 breeding pairs. We tracked the adults with geolocators over the subsequent year and combined migration route data with at‐sea activity budgets obtained from high‐resolution saltwater‐immersion data. Migratory behaviour was also recorded during non‐experimental years (the year before and/or two years after manipulation) for a subset of birds, allowing comparison between experimental and non‐experimental years within treatment groups.All birds cared for chicks until normal fledging age, resulting in birds with a longer breeding period delaying their departure on migration; however, birds that finished breeding earlier did not start migrating earlier. Increased reproductive effort resulted in less time spent at the wintering grounds, a reduction in time spent resting daily and a delayed start of breeding with lighter eggs and chicks and lower breeding success the following breeding season. Conversely, reduced reproductive effort resulted in more time resting and less time foraging during the winter, but a similar breeding phenology and success compared with control birds the following year, suggesting that ‘positive’ carry‐over effects may also occur but perhaps have a less long‐lasting impact than those incurred from increased reproductive effort.Our results shed light on how carry‐over effects can develop and modify an adult animal's behaviour year‐round and reveal how a complex interaction between current and future reproductive fitness, individual condition and external constraints can influence life‐history decisions.

Costs of breeding are rapidly buffered and do not affect migratory behavior in a long‐lived bird species

“…, Fayet et al. ). Alternatively, this could be a result of flight impairment due to an advance in their molt schedule (Cherel et al.…”

“…, Fayet et al. ). Theoretically, life history theory predicts that short‐lived species, with lower chances to survive until the next breeding attempt than long‐lived species, should invest as much as possible in current reproductive events, even when this effort may compromise their survival for future breeding attempts (Lindén and Moller , Stearns ).…”

“…, Fayet et al. ). Such failed breeder birds may simply fly less because of their better body condition and because their energetic demands are lower throughout the non‐breeding period (Daunt et al.…”

Linking oceanographic conditions, migratory schedules and foraging behaviour during the non‐breeding season to reproductive performance in a long‐lived seabird

“…Previous studies have reported that birds having a higher foraging activity during winter were more likely to fail to reproduce during the subsequent breeding season (Daunt et al., ; Kazama et al., ; Shoji et al., ). Individuals seemed therefore to adapt their winter foraging effort as a constrained response to their own body condition rather than as an active decision concerning future breeding (Fayet et al., ; Shoji et al., ).…”

Tracking Cairns: Biologging Improves the Use of Seabirds as Sentinels of the Sea

“…A major advantage of biologging is the potential to estimate food supply over multiple spatial and temporal scales. Year-round biologger deployments (e.g., Daunt et al, 2014;Fayet et al, 2016) can document year-round variation in food supply over large scales. Repeated biologger deployments on the same individuals over multiple years (e.g., Daunt et al, 2014) will allow us to examine inter-and intra-individual responses to variation in food supply.…”