Declining health status of Brown Skua (Stercorarius antarcticus lonnbergi) parents and their offspring during chick development

Abstract

During breeding, Brown Skuas (Stercorarius antarcticus lonnbergi) perform a great physical effort in the care and maintenance of the nest. Interestingly, the breeding colony on which this work was conducted is in steady decline in recent years. In order to understand the physiological background responsible for the trade off between reproductive effort and health status, in adults and the possible reasons for the colony decline, we evaluated the health status in Brown Skuas parents and growing chicks and blood samples were obtained in three different breeding stages from adults: In (incubation), Er (after egg hatching), and Lr (during chick rearing) and from developing chicks. Serum albumin, α-, β-. and γ-globulin fractions, IgY level and corticosterone were determined in adults, while plasma proteins concentration, electrolytes, and γ-globulins were determined in chicks. Differences in albumin, α-, and γ-globulins and IgY levels were observed in adults through the reproductive stages, indicating a decline in nutritional status and immunocompetence during breeding. In addition, a decline in body condition and immune status was observed in growing chicks, indicating a close relationship between the decrease of the health status and reproductive effort performed by adults and the physiological status of the nestlings during development.

Dynamics of circulating lipoproteins and lipids in Brown Skua (Stercorarius antarcticus lonnbergi) during the breeding cycle

“…Once fat stores have been exhausted, protein utilization increases. Previous works revealed that when lipid stores are low, Brown Skuas shift towards protein catabolism to meet their energy requirements (Graña ) which has been demonstrated in other studies as well (Ibañez et al 2018). The induction of protein catabolism could indicate that female skuas were in 1 3…”

“…Three reproductive stages were defined: egg incubation (In), early rearing (Er) and late rearing (Lr) (Fig. 1) (Graña Ibañez et al 2018). For In, sampling was done during incubation of eggs.…”

“…On the other hand, a better nutritional condition at the beginning of the breeding cycle or an increase in the transport of fats from stores to fuel high-energy expenditure processes as the egg incubation may induce an increase of VLDL abundance (Jenni-Eiermann and Jenni 1992). Afterwards, the decrease of VLDL levels may be associated with the decline of the nutritional status and body condition (Graña Ibañez et al 2018). Stored lipids and proteins may be used as fuel when insufficient energy incomes from diet.…”

“…During reproduction a division of labour in adults occurs (Furness 1987), in which males conduct a greater share of foraging to feed females and growing chicks (Burton 1968;Devillers 1978). Previous studies have described a decline of the nutritional and health status of Brown Skuas during breeding as a consequence of parental effort (Graña Grilli et al 2018;Ibañez et al 2018). Besides, diet studies during the breeding season have revealed that Brown Skuas often display a flexible foraging behaviour which enables them to supplement terrestrial prey with others from the sea (i.e.…”

Blood antioxidant status of Stercorarius maccormicki and Stercorarius antarcticus from Potter Peninsula, 25 de Mayo (King George) Island, Antarctica

“…Adults with a better body condition will possibly have more resources to be reallocated to avoid oxidative damage. It was previously described for breeding Brown Skuas during the intensive care of chicks that body mass and overall nutritional status decline because of the parental effort (Ibañez et al 2018;Graña Grilli et al 2018). During these breeding activities, a trade-off between oxidative stress damage and other physiological functions occur.…”