Parents are a Drag: Long-Lived Birds Share the Cost of Increased Foraging Effort with Their Offspring, but Males Pass on More of the Costs than Females

Jacobs, Shoshanah; Elliott, Kyle H.; Gaston, Anthony J.

doi:10.1371/journal.pone.0054594

Cited by 25 publications

(23 citation statements)

References 99 publications

(168 reference statements)

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“…When handicapped, female Brünnich's Guillemots Uria lomvia lost more weight than males, but their chicks’ growth did not decrease as much as that of handicapped males (Jacobs et al . ). Similarly, after rearing experimentally enlarged broods, Black‐legged Kittiwake females but not males had a lower body mass, resulting in a higher mortality of that sex (Jacobsen et al .…”

Section: Discussionmentioning

confidence: 97%

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Sex allocation and sex‐specific parental investment in an endangered seabird

Spelt

Pichegru

2017

Ibis

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Biased offspring sex ratio is relatively rare in birds and sex allocation can vary with environmental conditions, with the larger and more costly sex, which can be either the male or female depending on species, favoured during high food availability. Sex‐specific parental investment may lead to biased mortality and, coupled with unequal production of one sex, may result in biased adult sex ratio, with potential grave consequences on population stability. The African Penguin Spheniscus demersus, endemic to southern Africa, is an endangered monogamous seabird with bi‐parental care. Female adult African Penguins are smaller, have a higher foraging effort when breeding and higher mortality compared with adult males. In 2015, a year in which environmental conditions were favourable for breeding, African Penguin chick production on Bird Island, Algoa Bay, South Africa, was skewed towards males (1.5 males to 1 female). Males also had higher growth rates and fledging mass than females, with potentially higher post‐fledging survival. Female, but not male, parents had higher foraging effort and lower body condition with increasing number of male chicks in their brood, thereby revealing flexibility in their parental strategy, but also the costs of their investment in their current brood. The combination of male‐biased chick production and higher female mortality, possibly at the juvenile stage as a result of lower parental investment in female chicks, and/or at the adult stage as a result of higher parental investment, may contribute to a biased adult sex ratio (ASR) in this species. While further research during years of contrasting food availability is needed to confirm this trend, populations with male‐skewed ASRs have higher extinction risks and conservation strategies aiming to benefit female African Penguin might need to be developed.

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Section: Discussionmentioning

confidence: 97%

“…As long‐lived species, seabirds are expected to favour a fixed investment, but often male and female parents show different strategies (Jacobs et al . ). Often females, but not males, adjust their food provisioning behaviour to their brood size or begging behaviour of their chicks (e.g.…”

mentioning

confidence: 97%

Sex allocation and sex‐specific parental investment in an endangered seabird

Spelt

Pichegru

2017

Ibis

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“…In fact, responses to wing-clipping are highly variable. In some studies, handicapped birds often reduce their provisioning rate and have lower productivity (Jacobs et al 2013;Slagsvold and Lifjeld 1988;Tremblay et al 2003), but, perhaps as a consequence, do not have different return rates than non-manipulated birds (Bijleveld and Mullers 2009;Wright and Cuthill 1989). However, in other studies, even though wing-clipped birds reduced provisioning rates, they had lower return rates either with no difference in productivity (Winkler and Allen 1995) or even with a decrease in current productivity [Love and Williams (2008); see Fig.…”

Section: Experimental Manipulation Of Workload In Free-livingmentioning

confidence: 95%

Individual variation in workload during parental care: can we detect a physiological signature of quality or cost of reproduction?

Williams

Fowler

2015

J Ornithol

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How hard do birds work during parental care, chick rearing, or provisioning of their nestlings? And if birds do work hard, can we detect a physiological signature of individual variation in workload ability (perhaps related to 'quality') or costs associated with high workload? Here, we provide a broad conceptual perspective on these questions. Life-history theory predicts (or requires) that (1) parental care is hard work, (2) individuals that invest more in parental care benefit in terms of rearing more, larger, fitter offspring, but that (3) increased investment in parental care comes at a cost: decreased future fecundity and/or survival. However, we start by highlighting studies that are inconsistent with this conventional view, e.g., (1) females often do not pay a survival cost of increased workload (though males do), (2) some (high quality?) individuals appear to maximise numerous life-history traits, and (3) workload during parental care often does not predict productivity. We suggest that an ''exercise physiology'' perspective on parental care might be informative, but highlight the fact that existing models of exercise often involve conditions very different from that free-living animals experience while foraging (e.g., using forced exercise) and are often divorced from the critical relationship in free-living animals between exercise and acquisition of resources. We briefly review studies looking at physiological effects of workload during parental care in freeliving birds, but again highlight our surprising lack of knowledge in this area especially where experimental manipulation of workload is coupled with comprehensive, physiological analysis. Finally, we make three recommendations for how can we advance the study of physiology of parental care in chick-rearing birds: (1) experimental manipulation of workload, (2) obtaining better measures of workload, for large numbers of knownindividuals, and (3) better assessment of physiology of individual quality, and identification of specific metrics of workload-induced 'wear and tear'.

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“…), parental care (Jacobs et al. ), site fidelity (Becker et al. ), or other ecological traits that influence their demographic rates.…”

Section: Introductionmentioning

confidence: 99%

Sex‐biased survival contributes to population decline in a long‐lived seabird, the Magellanic Penguin

Gownaris

Boersma

2019

Ecological Applications

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We developed a Hidden Markov mark–recapture model (R package marked) to examine sex‐specific demography in Magellanic Penguins (Spheniscus magellanicus). Our model was based on 33 yr of resightings at Punta Tombo, Argentina, where we banded ~44,000 chicks from 1983 to 2010. Because we sexed only 57% of individuals over their lifetime, we treated sex as an uncertain state in our model. Our goals were to provide insight into the population dynamics of this declining colony, to inform conservation of this species, and to highlight the importance of considering sex‐specific vital rates in demographic seabird studies. Like many other seabirds, Magellanic Penguins are long‐lived, serially monogamous, and exhibit obligate biparental care. We found that the non‐breeding‐season survival of females was lower than that of males and that the magnitude of this bias was highest for juveniles. Biases in survival accumulated as cohorts aged, leading to increasingly skewed sex ratios. The survival bias was greatest in years when overall survival was low, that is, females fared disproportionality worse when conditions were unfavorable. Our model‐estimated survival patterns are consistent with independent data on carcasses from the species’ non‐breeding grounds, showing that mortality is higher for juveniles than for adults and higher for females than for males. Juveniles may be less efficient foragers than adults are and, because of their smaller size, females may show less resilience to food scarcity than males. We used perturbation analysis of a population matrix model to determine the impact of sex‐biased survival on adult sex ratio and population growth rate at Punta Tombo. We found that adult sex ratio and population growth rate have the greatest proportional response, that is, elasticity, to female pre‐breeder and adult survival. Sex bias in juvenile survival (i.e., lower survival of females) made the greatest contribution to population declines from 1990 to 2009. Because starvation is a leading cause of morality in juveniles and adults, precautionary fisheries and spatial management in the region could help to slow population decline. Our data add to growing evidence that knowledge of sex‐specific demography and sex ratios are necessary for accurate assessment of seabird population trends.

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Parents are a Drag: Long-Lived Birds Share the Cost of Increased Foraging Effort with Their Offspring, but Males Pass on More of the Costs than Females

Cited by 25 publications

References 99 publications

Sex allocation and sex‐specific parental investment in an endangered seabird

Sex allocation and sex‐specific parental investment in an endangered seabird

Individual variation in workload during parental care: can we detect a physiological signature of quality or cost of reproduction?

Sex‐biased survival contributes to population decline in a long‐lived seabird, the Magellanic Penguin

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