The influence of environmental conditions on the age pattern in breeding performance in a transequatorial migratory seabird

Anderson

2021

Ecology

Age and environment are important determinants of reproductive parameters in long‐lived organisms. These factors may interact to determine breeding responses to environmental change, yet few studies have examined the environmental dependence of aging patterns across the entire life span. We do so, using a 20‐yr longitudinal data set of reproductive phenotypes in long‐lived female Nazca boobies (Sula granti), a monogamous seabird breeding in the eastern tropical Pacific. Young and old females may suffer from inexperience and senescence, respectively, and/or practice reproductive restraint. Breeding performance (for breeding participation, breeding date, clutch size, egg volume, and offspring production) was expected to be lower in these age classes, particularly under environmental challenge, in comparison with middle‐aged breeders. Sea surface temperature anomalies (SSTA) represented interannual variation in the El Niño–Southern Oscillation (ENSO) and were one proxy for environmental quality (a population count of clutch initiations was a second). Although only females lay eggs, both sexes care for eggs and nestlings, and the male partner’s age, alone or in interaction with female age, was evaluated as a predictor of breeding performance. Middle‐aged females performed better than young and old birds for all reproductive traits. Pairing with a young male delayed breeding (particularly for old females) and reduced clutch size, and pairing with an old male reduced offspring production. Challenging environments increased age effects on breeding probability and breeding date across young to middle ages and for offspring production across middle to old ages. However, important exceptions to the predicted patterns for clutch size and fledging success across young to middle ages suggested that trade‐offs between fitness components may complicate patterns of trait expression across the life span. Relationships between breeding participation, environment, and individual quality and/or experience in young females may also contribute to unexpected patterns for clutch size and fledging success, traits expressed only in breeders. Finally, independent of age, breeding responses of female Nazca boobies to the ENSO did not follow expectations derived from oceanic forcing of primary productivity. During El Niño‐like conditions, egg‐laying traits (clutch size, breeding date) improved, but offspring production declined, whereas La Niña‐like conditions were “poor” environments throughout the breeding cycle.

Section: Discussionmentioning

confidence: 99%

“…2014]) and Scopoli’s shearwater ( Calonectris diomedea [Hernández et al. 2015]). Detecting within‐individual aging patterns (the focus of this study), and evaluating their interaction with the environment is best accomplished using longitudinal approaches that control individual heterogeneity (Cam et al.…”

Section: Introductionmentioning

confidence: 99%

Breeding responses to environmental variation are age‐ and trait‐dependent in female Nazca boobies

Anderson

2021

Ecology

“…However, our study shows that the form taken by age-environment interactions can vary considerably, even within a population. Diminished – not enhanced – age effects on breeding performance in a resource-poor environment have been observed for clutch size, egg volume, and hatching success in Audouin’s gulls (Oro et al 2014), for breeding date and egg volume in Scopoli’s shearwaters (Hernández et al 2015), and now for Clutch Size and Fledging Success in Nazca boobies.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, harsh environments may shrink age-related differences in Clutch Size, for example, if young individuals in relatively poor condition (due to inexperience or low quality) fail to breed (e.g., Weimerskirch 1992, Becker andBradley 2007). This explanation has been proposed by Oro et al (2014) and Hernández et al (2015) to explain larger age-related differences in breeding performance under high resource availability, although neither study explicitly evaluated breeding participation. Middle-aged Nazca boobies rarely skip breeding, while young birds are increasingly likely to skip in a poor versus a good environment (Fig.…”

Section: Interactions Between Age and Environmentmentioning

confidence: 99%

“…Accordingly, the pregnancy rates of yearling versus adult red deer ( Cervus elaphus ) diverge at high population density (Bonenfant et al 2002) and the largest performance discrepancies between the offspring production of young versus middle-aged birds occur under low food availability in Western gulls ( Larus occidentalis ; Sydeman et al 1991), and Australasian gannets ( Morus serrator ; Bunce et al 2005). However, not all studies find age-dependent responses to environmental variation (e.g., Nevoux et al 2007, Vieyra et al 2009) and two studies have revealed the opposite pattern: poor environments shrink, not accentuate, age-related differences in breeding performance for Audouin’s gulls ( Larus audouinii ; Oro et al 2014) and Scopoli’s shearwater ( Calonectris diomedea ; Hernández et al 2015). Detecting within-individual aging patterns (the focus of this study), and evaluating their interaction with the environment, is best accomplished using longitudinal approaches that control individual heterogeneity (Cam et al 2002, van de Pol and Verhulst 2006).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Breeding responses to environmental variation are age- and trait-dependent in female Nazca boobies

Anderson

2021

Preprint

Age and environment are important determinants of reproductive parameters in long-lived organisms. These factors may interact to determine breeding responses to environmental change, yet few studies have examined the environmental-dependence of aging patterns across the entire lifespan. We do so, using a 20-year longitudinal dataset of reproductive phenotypes in long-lived female Nazca boobies (Sula granti), a monogamous seabird breeding in the eastern tropical Pacific. Young and old females may suffer from inexperience and senescence, respectively, and/or practice reproductive restraint. Breeding performance (for breeding participation, breeding date, clutch size, egg volume, and offspring production) was expected to be lower in these age classes, particularly under environmental challenge, in comparison with middle-aged breeders. Sea surface temperature anomalies (SSTA) represented interannual variation in the El Niño-Southern Oscillation (ENSO) and were one proxy for environmental quality (a population count of clutch initiations was a second). Although only females lay eggs, both sexes care for eggs and nestlings, and the male partner′s age, alone or in interaction with female age, was evaluated as a predictor of breeding performance. Middle-aged females performed better than young and old birds for all reproductive traits. Pairing with a young male delayed breeding (particularly for old females) and reduced clutch size, and pairing with an old male reduced offspring production. Challenging environments increased age effects on breeding probability and breeding date across young to middle ages and for offspring production across middle to old ages. However, important exceptions to the predicted patterns for clutch size and fledging success across young to middle ages suggested trade-offs between fitness components may complicate patterns of trait expression across the lifespan. Relationships between breeding participation, environment, and individual quality and/or experience in young females may also contribute to unexpected patterns for clutch size and fledging success, traits expressed only in breeders. Finally, independent of age, breeding responses of female Nazca boobies to the ENSO did not follow expectations derived from oceanic forcing of primary productivity. During El Niño-like conditions, egg-laying traits (clutch size, breeding date) improved but offspring production declined, while La Niña-like conditions were ″poor″ environments throughout the breeding cycle.

Age effects on Nazca booby foraging performance are largely constant across variation in the marine environment: Results from a 5‐year study in Galápagos

McKee

Estela

et al. 2023

Ecology and Evolution

Foraging outcomes dictate the nutritional resources available to an organism and may vary with intrinsic factors, like age. Thus, understanding how age affects foraging performance, alone or in interaction with extrinsic factors (like environmental quality), improves our understanding of aging processes in the wild. We examined how foraging traits, measured across five breeding seasons, change with age, environmental variation, and their interaction in Nazca boobies (Sula granti), a pelagic seabird in Galápagos. We evaluated the hypotheses that (1) foraging performance is better in middle-aged birds than in young ones, and that (2) foraging performance is better in middle-aged birds than in old ones. Furthermore, favorable environmental conditions will either (3) attenuate age differences in foraging performance (by relieving constraints on young, inexperienced and old, senescent age classes), or (4) accentuate age differences (if middle-aged birds can exploit abundant resources better than other age classes can). Incubating birds tagged with GPS loggers (N = 815) provided data on foraging performance (e.g., total distance traveled, mass gained) to evaluate interactions between age and environmental variation (e.g., sea surface temperature). Poor environmental conditions associated with the cool phase of the El Niño-Southern Oscillation increased foraging effort, including foraging distance and duration, for example. Across age classes, foraging boobies responded similarly to environmental variation except for female mass gain rate: age-related declines in mass gain rate were reduced under favorable environmental conditions. Birds of different ages also searched in somewhat distinct areas in the poor conditions of 2016, but not in other years. In several foraging traits, including foraging duration and distance, female boobies showed predicted early-life improvement and late-life decline, following the established pattern for reproductive traits in this species. Thus, deficits in resource acquisition (this study) may contribute to the poor survival and reproductive outcomes previously observed in old Nazca boobies, particularly in females.underlying foraging traits (mass gain, foraging duration; following Howard et al., 2021), and, for the first time, for foraging location, distance traveled, and time spent searching. We evaluate age-byenvironment interactions with respect to a population-level shift in breeding date (Tompkins et al., 2017) and two environmental predictors linked to the El Niño-Southern Oscillation (ENSO; sea surface temperature and cloud cover; Table 1). Using patterns of observed age effects in breeding traits as models (Tompkins et al., 2017;Tompkins & Anderson, 2019, 2021, and assuming a tight link between foraging and breeding performances, we predict that: (1) foraging performance will be better in middle-aged birds than in young ones in our cross-sectional sample (higher rate of mass gain, larger mass gain, and shorter foraging duration, distance traveled, and time searching in middle-aged...