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

Abstract

Life history theory states that individual fitness in one stage of life is conditioned by what occurred in previous stages. In migratory species, reproductive effort during breeding has often been found to influence body condition, molt schedule, self-provisioning and migration of individuals in subsequent seasons (i.e., carryover effects of breeding). However, there is a current uncertainty in understanding how long-distance migrants trade off among such energy-demanding activities (i.e., breeding, molting and migrating). To provide evidence to the field, we experimentally reduced the parental effort of a long-lived Procellariform, the Cory's shearwater (Calonectris borealis), by inducing failure at the incubation stage. Treatment and control birds were tracked during their subsequent migration by means of light-level and immersion loggers and sampled for six specific feathers (molted at different periods along the migratory cycle) upon the recovery of the loggers 1 yr later. Feathers were used to perform stable isotope analysis (SIA) and determine corticosterone levels (CORT). By these means, we evaluated the effect of breeding effort on migratory strategy, at-sea activity patterns, molt patterns, and levels of stress experienced by birds along the non-breeding period. We did not detect any difference between birds in the induced failure group and successful breeders in terms of spatio-temporal distribution: all birds shared common foraging areas throughout the study period and the timing of major phenological events did not differ. Failed birds significantly advanced their molt, as revealed by SIA and flying activity patterns. The stress levels of failed birds, inferred through CORT concentrations in feathers, were found to be consistently lower than in successful breeders, through the end of the breeding to the non-breeding period. Thus, we provide robust evidence that the costs of reproduction can be physiologically mediated from the breeding to the non-breeding period through molting schedules and CORT levels. However, we failed to detect clear effects on migratory behavior or subsequent breeding success, suggesting that costs of breeding in long-lived species may be rapidly buffered during the post-breeding period, as would be expected from life history theory.

Effect of breeding performance on the distribution and activity budgets of a predominantly resident population of black‐browed albatrosses

“…As expected, resident black-browed albatrosses decreased their general activity well before the end of the chick-rearing period and did ing ground, as other migratory procellariiform species usually do (e.g., Fayet et al, 2016;Gutowsky et al, 2014;Mackley et al, 2010;Péron et al, 2010;Ramos et al, 2018). Breeding status also strongly affected the temporal dynamics of activity budgets.…”

“…Those results suggests that the response to breeding failure was an earlier change in time and energy allocation strategies: Successful breeders recovered from potential reproductive costs by allocating more time to foraging by day and night at the end of the chick‐rearing period and conversely delayed and reduced the duration of their resting period, when floating activity was maximum. On the contrary, failed breeders did not increase their foraging effort but rapidly decreased their general activity by spending more time floating on the water and less time flying and for a longer period, especially during daylight, which potentially allowed them to molt earlier and have more time to recover from those costs (Catry, Poisbleau, et al, ; Ramos et al, ). These readjustments in activity budgets contrast with a recent study carried out on migrant black‐browed albatrosses nesting in Kerguelen (Southern Indian Ocean) that described a different effect of breeding failure on individual activity budgets (Desprez et al, ): Failed individuals increased their foraging effort, potentially because of a lower body condition.…”

“…Foraging activities of failed females were even lower than other groups, suggesting that they did not need to feed more to compensate a potentially lower body condition. Consequently, residency may help accelerate buffering of reproductive costs, especially if environmental conditions are favorable (Ramos et al, ).…”

“…For example, individual Cory's shearwaters Calonectris borealis breeding in Selvagem Grande (Madeira archipelago) spend their nonbreeding season in five different areas (Dias, Granadeiro, & Catry, 2012) while individuals from this species breeding in other colonies converge to the same nonbreeding grounds (González-Solís, Croxall, Oro, & Ruiz, 2007). Likewise, individuals from some populations may migrate thousands of kilometers while others remain relatively sedentary (Pérez, Granadeiro, Dias, Alonso, & Catry, 2014;Ramos, Llabrés, Monclús, López-Béjar, & González-Solís, 2018;Weimerskirch, Delord, Guitteaud, Phillips, & Pinet, 2015). This is notably the case of the black-browed albatross Thalassarche melanophris.…”

“…Indeed, as failed breeders are relieved from reproductive duties earlier than individuals that successfully fledge a chick, they do not suffer from the same potential reproductive costs (Golet, Schmutz, Irons, & Estes, 2004;Ramos et al, 2018). Failed breeders have notably been shown to leave the colony earlier than successful breeders (Bogdanova et al, 2011;Catry, Dias, Phillips, & Granadeiro, 2013a;Desprez et al, 2018) and use different nonbreeding grounds (Bogdanova et al, 2011;Catry, Dias, et al, 2013a;Clay et al, 2016;Hoye, Hahn, Nolet, & Klaassen, 2012), which may directly influence their activity budgets, both at the end of the breeding season and during the subsequent nonbreeding season (Ramos et al, 2018). In migrant black-browed albatrosses, failed breeders have notably been shown to forage more during the nonbreeding season (Desprez et al, 2018).…”