Environmental influences on Adelie penguin breeding schedules, endocrinology, and chick survival

Non-breeding feather concentrations of testosterone, corticosterone and cortisol are associated with subsequent survival in wild house sparrows

“…However, in a majority of these studies, plasma GC levels were elevated by restraint, implants or hormonal stimulation. In the rare studies where baseline plasma GC levels were obtained, the association with survival has been inconsistent [6,35,36]. Here, we avoid confounding effects of the sampling procedure on the steroids of interest, and avoid relying on a single moment in time to represent dynamic steroid exposures, by using feather samples.…”

Seasonal changes in reproductive anatomy and gonadal hormone concentrations of African penguins (Spheniscus demersus)

“…Even though there have been numerous studies on penguin breeding ecology and sperm cryopreservation, only limited information is available on reproductive biology of penguins, in particular studies related to macro-and micro-anatomy of the reproductive organs (Boersma, 1978;Gee et al, 2004;Ancel et al, 2013;O'Brien et al, 2016). In terms of reproductive endocrinology, several research groups have reported seasonal changes in plasma concentrations of testosterone and 17β-estradiol for various penguin species, but respective data for the African penguin are lacking (Williams, 1992;Cherel et al, 1994;Cockrem and Seddon, 1994;Fowler et al, 1994;McQueen et al, 1998;Otsuka et al, 1998;Ninnes et al, 2011). The aim of the present study was to address this scarcity of information by investigating the structural aspects of the male and female reproductive tracts of African penguins.…”

Delay in Adélie penguin nest occupation restricts parental investment in nest construction and reduces reproductive output

“…This regional population, currently numbering around 190,000 breeding pairs, has increased substantially over the past six decades with a recent slowing likely due to breeding habitat limitations or food availability through intraspecific competition (Southwell et al, 2021). In contrast to other East Antarctic locations where fast ice is extensive and is a primary driver of reproductive success (Barreau et al, 2019;Emmerson & Southwell, 2008;Ninnes et al, 2011), the Windmill Islands has relatively little fast ice present next to their colonies during the penguin breeding season. Therefore, we expect that reproductive success in this region will be driven by environmental and behavioural factors other than fast ice, although it is not clear whether these factors are marine and climatic, terrestrial or behavioural, and under what conditions reproductive success increases with greater parental investment.…”

“…Previous studies have found that Adélie penguin reproductive success can be influenced by external factors operating in their marine and terrestrial environments. For example, reproductive success can be negatively impacted by the presence of extensive fast ice adjacent to their colonies which forces the penguins to walk across ice to their foraging grounds, requiring more time and energy, in numerous sites including Pointe Géologie (Barreau et al., 2019 ), Béchervaise Island (Emmerson & Southwell, 2008 ), Lutzow‐Holm Bay (Kato et al., 2002 ) and at Ross Island in the Ross Sea (Ninnes et al., 2011 ). Reduced pack ice can also influence reproductive success through reduced foraging success, resulting from less under‐ice microalgal communities that sustain krill populations (Barreau et al., 2019 ).…”