Preliminary investigation of the costs of incubation in the Australasian Gannet (<i>Morus serrator</i>) breeding in Port Phillip Bay, Victoria

Ewing, A. D.; Norman, F.I.; Ward, Simon; Bunce, Ashley

doi:10.1071/mu03061

Cited by 7 publications

(4 citation statements)

References 48 publications

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“…The maintenance of body condition is a common feature of most experimental studies that manipulated reproductive costs in long-lived bird species (see Table 1). Similar to the results found in the present study, in most cases handicapped birds maintained their body mass during the incubation and during the chick-rearing period (Mauck and Grubb 1995;Tveraa et al 1997;Weimerskirch et al 1999;Duriez et al 2000;Nisbet et al 2004;Ewing et al 2005), and apparently transferred the extra breeding cost to the partner or to the chicks. Unlike previous studies, we assessed the nutritional state of the birds through the analysis of blood biochemical parameters related to the dynamics of protein (total protein, uric acid and urea) and fat stores (triglycerides) (Jenni-Eiermann and Jenni 1998; Totzke et al 1999;Alonso-Álvarez et al 2002).…”

Section: Discussionsupporting

confidence: 93%

“…Table 1 Study period, manipulation type and diVerent variables used in the present and other studies of an experimental increase in reproductive eVort in seabirds X refers to the study period and type of manipulation to increase the eVort. Zero and one refer to non-signiWcant or signiWcant eVects, respectively of the studied variable a Granadeiro et al (1998), b Weimerskirch et al (2000, c Weimerskirch et al (1997), d Mínguez (1998), e Ewing et al (2005), f Mauck and Grubb (1995) …”

Section: Model Speciesmentioning

confidence: 98%

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Experimental increase of flying costs in a pelagic seabird: effects on foraging strategies, nutritional state and chick condition

Navarro

González‐Solís

2006

Oecologia

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A central point in life history theory is that parental investment in current reproduction should be balanced by the costs in terms of residual reproductive value. Long-lived seabirds are considered fixed investors, that is, parents fix a specific level of investment in their current reproduction independent to the breeding requirements. We tested this hypothesis analysing the consequences of an experimental increase in flying costs on the foraging ecology, body condition and chick condition in Cory's shearwaters Calonectris diomedea. We treated 28 pairs by reducing the wing surface in one partner and compared them with 14 control pairs. We monitored mass changes and incubation shifts and tracked 19 foraging trips per group using geolocators. Furthermore, we took blood samples at laying, hatching and chick-rearing to analyse the nutritional condition, haematology, muscle damage and stable isotopes. Eighty-day-old chicks were measured, blood sampled and challenged with PHA immune assay. In addition, we analysed the effects of handicap on the adults at the subsequent breeding season. During incubation, handicapped birds showed a greater foraging effort than control birds, as indicated by greater foraging distances and longer periods of foraging, covering larger areas. Eighty-day-old chicks reared by treated pairs were smaller and lighter and showed a lower immunity than those reared by control pairs. However, oxygen demands, nutritional condition and stable isotopes did not differ between control and handicapped birds. Although handicapped birds had to increase their foraging effort, they maintained physical condition by reducing parental investment and transferred the experimentally increased costs to their partners and the chick. This result supports the fixed investment hypothesis and is consistent with life history theory.

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Section: Discussionsupporting

confidence: 93%

Section: Model Speciesmentioning

confidence: 98%

Experimental increase of flying costs in a pelagic seabird: effects on foraging strategies, nutritional state and chick condition

Navarro

González‐Solís

2006

Oecologia

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“…In Sulids, no validation of body condition as a measure of total body fat exists. Studies relating to body condition report either body mass [ 74 , 75 ] or an index with body mass regressed against wing length, tarsus or culmen length [ 26 , 76 – 78 ]. Furthermore, across studies of the same species these indices have not been consistent and, hence, comparison is not possible.…”

Section: Discussionmentioning

confidence: 99%

Sexual Size Dimorphism and Body Condition in the Australasian Gannet

et al. 2015

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Sexual size dimorphism is widespread throughout seabird taxa and several drivers leading to its evolution have been hypothesised. While the Australasian Gannet (Morus serrator) has previously been considered nominally monomorphic, recent studies have documented sexual segregation in diet and foraging areas, traits often associated with size dimorphism. The present study investigated the sex differences in body mass and structural size of this species at two colonies (Pope’s Eye, PE; Point Danger, PD) in northern Bass Strait, south-eastern Australia. Females were found to be 3.1% and 7.3% heavier (2.74 ± 0.03, n = 92; 2.67 ± 0.03 kg, n = 43) than males (2.66 ± 0.03, n = 92; 2.48 ± 0.03 kg, n = 43) at PE and PD, respectively. Females were also larger in wing ulna length (0.8% both colonies) but smaller in bill depth (PE: 2.2%; PD: 1.7%) than males. Despite this dimorphism, a discriminant function provided only mild accuracy in determining sex. A similar degree of dimorphism was also found within breeding pairs, however assortative mating was not apparent at either colony (R 2 < 0.04). Using hydrogen isotope dilution, a body condition index was developed from morphometrics to estimate total body fat (TBF) stores, where TBF(%) = 24.43+1.94*(body mass/wing ulna length) – 0.58*tarsus length (r 2 = 0.84, n = 15). This index was used to estimate body composition in all sampled individuals. There was no significant difference in TBF(%) between the sexes for any stage of breeding or in any year of the study at either colony suggesting that, despite a greater body mass, females were not in a better condition than males. While the driving mechanism for sexual dimorphism in this species is currently unknown, studies of other Sulids indicate segregation in foraging behaviour, habitat and diet may be a contributing factor.

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“…Most studies that evaluated the energetic cost of breeding used changes in body condition or body mass alone. However, birds may compensate for variations in their body mass by increasing their foraging effort and energy intake (Ewing et al 2005 ) or reducing their energetic demands by decreasing their breeding investment (González-Medina et al 2015 ; Kidawa et al 2015 ; Storey et al 2017 ). Thus, considering plasma metabolites as indicators of nutritional state, in addition to changes in body mass, can provide valuable information.…”

Section: Introductionmentioning

confidence: 99%

Nutritional state variations in a tropical seabird throughout its breeding season

et al. 2022

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Individual body condition is frequently used to explain differences in foraging and breeding ecology in seabirds. However, little is known about the covariations of body mass with the nutritional state of animals as measured through plasma metabolites and how these different measures vary between and within individuals during breeding. Here, we assessed intra-individual variations of plasma metabolites (triglycerides, cholesterol, protein, and ß-hydroxybutyrate concentrations) and in body mass of Blue-footed boobies (Sula nebouxii) throughout their breeding season 2011–2012 in Isla El Rancho, Mexico. We found breeding-stage and sex-specific variations in individuals’ plasma metabolite concentrations, but these did not mirror variations in body mass. Before egg-laying, females had higher triglycerides, cholesterol, and protein concentrations than males. In contrast, males used their nutritional reserves (higher ß-hydroxybutyrate concentrations) more than females during the breeding season (except for early chick-rearing). At the individual level, males gained weight during the breeding season, whereas females lost weight. We also found that between-individual differences in plasma metabolite concentrations and changes in body mass were not consistent throughout the breeding season, while individual body mass was significantly repeatable. This study contributes to a better understanding of seabird breeding ecology and physiology by showing that sex-specific breeding roles might highly influence the nutritional state. Similar patterns might occur in other seabird species, helping to explain why we can find stage- and sex-specific foraging behaviors even in monomorphic species.

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Preliminary investigation of the costs of incubation in the Australasian Gannet (Morus serrator) breeding in Port Phillip Bay, Victoria

Cited by 7 publications

References 48 publications

Experimental increase of flying costs in a pelagic seabird: effects on foraging strategies, nutritional state and chick condition

Experimental increase of flying costs in a pelagic seabird: effects on foraging strategies, nutritional state and chick condition

Sexual Size Dimorphism and Body Condition in the Australasian Gannet

Nutritional state variations in a tropical seabird throughout its breeding season

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