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To address this hypothesis, we determined the breeding season prolactin profile of the yelloweyed penguin (Megadyptes antipodes) for comparison with those of other penguin species found in the literature. We also measured sex steroid plasma concentrations to better characterize the reproductive cycle of the species. Plasma concentrations of prolactin increased from early in the season, reaching a peak during late incubation, and remained elevated up to the guard period. This general pattern was similar to that of other penguins for which we have corresponding data. However, we found that throughout the laying period, prolactin titers in yellow-eyed penguins remained elevated while they fell to basal levels after the laying of the first egg in macaroni penguins, which corresponds to differences in incubation behavior during this time. We conclude, therefore, that differences in the brood reduction behavior in penguins, may be reflected in the pattern of PRL concentrations around the time of egg laying.","publication_date":"2006,,","publication_name":"Comparative Biochemistry and Physiology Part A: Molecular \u0026 Integrative Physiology","grobid_abstract_attachment_id":"39260550"},"document_type":"paper","pre_hit_view_count_baseline":null,"quality":"high","language":"en","title":"Hormonal correlates of parental behavior in yellow-eyed penguins (Megadyptes antipodes)","broadcastable":true,"draft":null,"has_indexable_attachment":true,"indexable":true}}["work"]; window.loswp.workCoauthors = [28790893]; window.loswp.locale = "en"; window.loswp.countryCode = "SG"; window.loswp.cwvAbTestBucket = ""; window.loswp.designVariant = "ds_vanilla"; window.loswp.fullPageMobileSutdModalVariant = "control"; window.loswp.useOptimizedScribd4genScript = false; window.loginModal = {}; window.loginModal.appleClientId = 'edu.academia.applesignon';</script><script defer="" src="https://accounts.google.com/gsi/client"></script><div class="ds-loswp-container"><div class="ds-work-card--grid-container"><div class="ds-work-card--container js-loswp-work-card"><div class="ds-work-card--cover"><div class="ds-work-cover--wrapper"><div class="ds-work-cover--container"><button class="ds-work-cover--clickable js-swp-download-button" data-signup-modal="{"location":"swp-splash-paper-cover","attachmentId":39260550,"attachmentType":"pdf"}"><img alt="First page of “Hormonal correlates of parental behavior in yellow-eyed penguins (Megadyptes antipodes)”" class="ds-work-cover--cover-thumbnail" src="https://0.academia-photos.com/attachment_thumbnails/39260550/mini_magick20190223-1672-1sv83dh.png?1550922426" /><img alt="PDF Icon" class="ds-work-cover--file-icon" src="//a.academia-assets.com/images/single_work_splash/adobe_icon.svg" /><div class="ds-work-cover--hover-container"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">download</span><p>Download Free PDF</p></div><div class="ds-work-cover--ribbon-container">Download Free PDF</div><div class="ds-work-cover--ribbon-triangle"></div></button></div></div></div><div class="ds-work-card--work-information"><h1 class="ds-work-card--work-title">Hormonal correlates of parental behavior in yellow-eyed penguins (Megadyptes antipodes)</h1><div class="ds-work-card--work-authors ds-work-card--detail"><a class="ds-work-card--author js-wsj-grid-card-author ds2-5-body-md ds2-5-body-link" data-author-id="28790893" href="https://uwa.academia.edu/GraemeMartin"><img alt="Profile image of Graeme B Martin" class="ds-work-card--author-avatar" src="https://0.academia-photos.com/28790893/8173977/23094994/s65_graeme.martin.jpg" />Graeme B Martin</a></div><div class="ds-work-card--detail"><p class="ds-work-card--detail ds2-5-body-sm">2006, Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology</p><div class="ds-work-card--work-metadata"><div class="ds-work-card--work-metadata__stat"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">visibility</span><p class="ds2-5-body-sm" id="work-metadata-view-count">…</p></div><div class="ds-work-card--work-metadata__stat"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">description</span><p class="ds2-5-body-sm">6 pages</p></div><div class="ds-work-card--work-metadata__stat"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">link</span><p class="ds2-5-body-sm">1 file</p></div></div><script>(async () => { const workId = 16925253; 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if (!viewCountBody) { throw new Error('Failed to find work views element'); } viewCountBody.textContent = `${commaizedViewCount} views`; } catch (error) { // Remove the whole views element if there was some issue parsing. document.getElementById('work-metadata-view-count')?.parentNode?.remove(); throw new Error(`Failed to parse view count: ${viewCount}`, error); } }; // If the DOM is still loading, wait for it to be ready before updating the view count. if (document.readyState === "loading") { document.addEventListener('DOMContentLoaded', () => { updateViewCount(viewCount); }); // Otherwise, just update it immediately. } else { updateViewCount(viewCount); } })();</script></div><p class="ds-work-card--work-abstract ds-work-card--detail ds2-5-body-md">Penguins show varying degrees of brood reduction behavior, from obligate brood reducers to brood maximizers, and we hypothesize that this is associated with differences in prolactin secretion. To address this hypothesis, we determined the breeding season prolactin profile of the yelloweyed penguin (Megadyptes antipodes) for comparison with those of other penguin species found in the literature. We also measured sex steroid plasma concentrations to better characterize the reproductive cycle of the species. Plasma concentrations of prolactin increased from early in the season, reaching a peak during late incubation, and remained elevated up to the guard period. This general pattern was similar to that of other penguins for which we have corresponding data. However, we found that throughout the laying period, prolactin titers in yellow-eyed penguins remained elevated while they fell to basal levels after the laying of the first egg in macaroni penguins, which corresponds to differences in incubation behavior during this time. We conclude, therefore, that differences in the brood reduction behavior in penguins, may be reflected in the pattern of PRL concentrations around the time of egg laying.</p><div class="ds-work-card--button-container"><button class="ds2-5-button js-swp-download-button" data-signup-modal="{"location":"continue-reading-button--work-card","attachmentId":39260550,"attachmentType":"pdf","workUrl":"https://www.academia.edu/16925253/Hormonal_correlates_of_parental_behavior_in_yellow_eyed_penguins_Megadyptes_antipodes_"}">See full PDF</button><button class="ds2-5-button ds2-5-button--secondary js-swp-download-button" data-signup-modal="{"location":"download-pdf-button--work-card","attachmentId":39260550,"attachmentType":"pdf","workUrl":"https://www.academia.edu/16925253/Hormonal_correlates_of_parental_behavior_in_yellow_eyed_penguins_Megadyptes_antipodes_"}"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">download</span>Download PDF</button></div></div></div></div><div data-auto_select="false" data-client_id="331998490334-rsn3chp12mbkiqhl6e7lu2q0mlbu0f1b" data-doc_id="39260550" data-landing_url="https://www.academia.edu/16925253/Hormonal_correlates_of_parental_behavior_in_yellow_eyed_penguins_Megadyptes_antipodes_" data-login_uri="https://www.academia.edu/registrations/google_one_tap" data-moment_callback="onGoogleOneTapEvent" id="g_id_onload"></div><div class="ds-top-related-works--grid-container"><div class="ds-related-content--container ds-top-related-works--container"><h2 class="ds-related-content--heading">Related papers</h2><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="0" data-entity-id="22415127" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/22415127/Effects_of_artificial_eggs_on_prolactin_secretion_steroid_levels_brood_patch_development_incubation_onset_and_clutch_size_in_the_yellow_eyed_penguin_Megadyptes_antipodes_">Effects of artificial eggs on prolactin secretion, steroid levels, brood patch development, incubation onset and clutch size in the yellow-eyed penguin (Megadyptes antipodes)</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="43897037" href="https://independent.academia.edu/DavisLloyd">Lloyd Davis</a></div><p class="ds-related-work--metadata ds2-5-body-xs">General and Comparative Endocrinology, 2007</p><p class="ds-related-work--abstract ds2-5-body-sm">Several studies have shown that the transition from egg laying to incubation behavior in birds is associated with changes in plasma levels of prolactin and steroid hormones. However, any eVect of the tactile and visual input provided by eggs at initiating these hormonal changes has not been fully investigated in wild birds. A few days before yellow-eyed penguins, Megadyptes antipodes, started egg laying, we placed an artiWcial egg into their nests or under cages next to their nest. We then investigated the eVect of the tactile and/or visual stimulus of such an artiWcial egg on prolactin secretion, steroid hormone levels (total androgen, estradiol and progesterone), brood patch development, incubation onset and clutch size in these penguins. Prolactin levels rose in females in response to having an artiWcial egg in the nest, while they declined considerably in males. Total androgen concentrations in males were less than 7% of those of control males and the levels prior to egg placement. Brood patch width increased in both males and females. Additionally, an egg in the nest caused yellow-eyed penguin pairs to attend and sit prone on their nest more frequently. Females that initiated egg laying 1 or 2 days after placement of the artiWcial egg in the nest, laid a full clutch of two eggs, while most other females that were exposed to an artiWcial egg in their nest, laid only a single egg. In contrast, the visual stimulus of an artiWcial egg alone (that was placed under a cage) did not inXuence hormone levels, brood patch development, incubation behavior or clutch size. The stimulation of an egg in the nest inXuences prolactin and total androgen levels in yellow-eyed penguins, particularly in males. While brood patch development and incubation behavior were initiated and egg laying was terminated in response to an artiWcial egg in the nest, the exact endocrine mechanisms underlying these physiological and behavioral changes remain poorly understood. We encourage further studies on other bird species taking an experimental approach to investigate the direct inXuence of hormones in initiating brood patch development and incubation behavior. Moreover, such experimental studies will widen our understanding of the endocrine mechanisms that regulate clutch size.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Effects of artificial eggs on prolactin secretion, steroid levels, brood patch development, incubation onset and clutch size in the yellow-eyed penguin (Megadyptes antipodes)","attachmentId":43038287,"attachmentType":"pdf","work_url":"https://www.academia.edu/22415127/Effects_of_artificial_eggs_on_prolactin_secretion_steroid_levels_brood_patch_development_incubation_onset_and_clutch_size_in_the_yellow_eyed_penguin_Megadyptes_antipodes_","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/22415127/Effects_of_artificial_eggs_on_prolactin_secretion_steroid_levels_brood_patch_development_incubation_onset_and_clutch_size_in_the_yellow_eyed_penguin_Megadyptes_antipodes_"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="1" data-entity-id="21664132" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/21664132/Endocrine_Correlates_of_Parental_Care_in_an_Antarctic_Winter_Breeding_Seabird_the_Emperor_Penguin_Aptenodytes_forsteri">Endocrine Correlates of Parental Care in an Antarctic Winter Breeding Seabird, the Emperor Penguin,Aptenodytes forsteri</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="42816241" href="https://independent.academia.edu/pierreJouventin">pierre Jouventin</a></div><p class="ds-related-work--metadata ds2-5-body-xs">Hormones and Behavior, 1999</p><p class="ds-related-work--abstract ds2-5-body-sm">Plasma levels of luteinizing hormone (LH) and prolactin associated with parental behavior were measured in the Antarctic winter breeding emperor penguin, Aptenodytes forsteri. Males exclusively incubate the egg while females exclusively brood the nonhomeothermic young; both sexes alternate in rearing the homeothermic young. Birds were sampled on arrival from the sea through egg laying, incubation, and brooding. All parent birds lost their chicks at the end of the brooding period due to harsh weather but sampling continued. In females, LH titers dropped after egg laying but levels were restored when the birds returned from the sea to brood the chicks and were not depressed by high prolactin levels. Plasma prolactin remained low in males captured on arrival and kept until the free-living males finished incubation. In breeders, prolactin secretion increased during the prelaying period when day length decreased. Prolactin levels stayed elevated in males during incubation and in brooding females returning after a 2-month absence at sea. Prolactin values were higher in brooding females than in males ending incubation or returning in late brooding. These levels did not drop after chick loss, and the sexual difference in prolactin values was maintained after breeding failure. In emperor penguins, increased prolactin secretion appears to be triggered around the time of egg laying and continues, driven by an endogenous mechanism, through incubation and brooding until rearing is completed. Prolactin secretion independent of external stimuli may have evolved in pelagic seabirds to maintain parental care despite long absences at sea from the breeding colony.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Endocrine Correlates of Parental Care in an Antarctic Winter Breeding Seabird, the Emperor Penguin,Aptenodytes forsteri","attachmentId":42330324,"attachmentType":"pdf","work_url":"https://www.academia.edu/21664132/Endocrine_Correlates_of_Parental_Care_in_an_Antarctic_Winter_Breeding_Seabird_the_Emperor_Penguin_Aptenodytes_forsteri","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/21664132/Endocrine_Correlates_of_Parental_Care_in_an_Antarctic_Winter_Breeding_Seabird_the_Emperor_Penguin_Aptenodytes_forsteri"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="2" data-entity-id="21664131" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/21664131/Parental_Care_and_the_Prolactin_Secretion_Pattern_in_the_King_Penguin_An_Endogenously_Timed_Mechanism">Parental Care and the Prolactin Secretion Pattern in the King Penguin: An Endogenously Timed Mechanism?</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="42816241" href="https://independent.academia.edu/pierreJouventin">pierre Jouventin</a></div><p class="ds-related-work--metadata ds2-5-body-xs">Hormones and Behavior, 1996</p><p class="ds-related-work--abstract ds2-5-body-sm">breeders, possibly preventing the birds from relaying, The King penguin (Aptenodytes patagonicus) has been but remain low in immature birds. These data raise quesstudied on Possession Island, Crozet Archipelago tions about how prolactin secretion is controlled in this (46Њ25S-51Њ45E). It is an offshore feeder, but it breeds species. The hypothesis of a programmed secretion of on land. Its breeding cycle is unusually long (about 14 prolactin is advanced. ᭧ 1996 Academic Press, Inc. months). It starts at the beginning of spring, is interrupted during 5 months of winter, and ends in the next spring. Furthermore, it is characterized by a long parental care period, of about 11 months, including the winter For many species, especially among mammals and interruption. In fact, care given to the egg and the chick birds, a reproductive effort is prolonged by parental is biparental, which supposes that parental behavior inbehavior. In its broadest sense, parental behavior includes both parents. Each parent alternates care given to the egg and to the chick on land and foraging bouts cludes the preparation of nests or burrows, the producat sea. An incubation bout, or a chick care bout, is called tion of the eggs, incubation, and the rearing of the a shift. Prolactin is the hypophyseal hormone known to young. This latter period is absent or very limited in be correlated with incubation and chick care. We studied precocial species , but in altricial ones, the mechanism of the maintenance of prolactin during it is more or less developed. In its more extended form, the parental care period in the King penguin, a period it includes the brood stage (the chick, not thermally which is unusually long. In many species, prolactin seemancipated, is still incubated), chick care (when the cretion has been shown to be stimulated by the presence chick can be left alone in the nest or in creche with of eggs and/or chicks, but in the King penguin, prolactin others), and postfledging care (despite the chick's abilsecretion is observed throughout the entire period of ity to fly or swim) (Burger, 1980). parental care, despite the fact that the birds leave the Since Riddle et al. (1935), an hypophyseal hormone, egg and the chick repeatedly and for extended periods of time to feed. Prolactin levels rise significantly at the prolactin, has been known to play an important role in beginning of courtship; females have significantly higher parental behavior. In numerous cases, this hormone prolactin levels than males during courtship, copulation, was said to be correlated with parental care, rising just and the period of waiting for egg laying. In both sexes, before incubation and dropping after hatching, in preprolactin levels remain high during incubation and the cocial species (duck: Hall and Goldsmith, 1983; hen: first part of chick rearing, before winter. Prolactin con-Zadworny et al., 1988) or dropping at the end of parencentrations decline somewhat during the winter period tal care (Rosenblatt, 1992) in altricial species. However, of minimal parental care, but remain that level in spring patterns of prolactin secretion do not seem to be so when parental care starts again. The level returns to strict or general (Open and Proudman, 1980; Phillips et basal value during molt. Prolactin levels rise during the al., 1985). For some species, incubation starts although incubation shifts but not over the course of contact with the prolactin level is not elevated (canary: Ball, 1991; young. Prolactin values remain high in unsuccessful Goldsmith, 1982; ring dove: Goldsmith et al., 1981), and the level of this hormone may drop although parents</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Parental Care and the Prolactin Secretion Pattern in the King Penguin: An Endogenously Timed Mechanism?","attachmentId":42330327,"attachmentType":"pdf","work_url":"https://www.academia.edu/21664131/Parental_Care_and_the_Prolactin_Secretion_Pattern_in_the_King_Penguin_An_Endogenously_Timed_Mechanism","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/21664131/Parental_Care_and_the_Prolactin_Secretion_Pattern_in_the_King_Penguin_An_Endogenously_Timed_Mechanism"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="3" data-entity-id="13271429" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/13271429/Decreasing_prolactin_levels_leads_to_a_lower_diving_effort_but_does_not_affect_breeding_success_in_Ad%C3%A9lie_penguins">Decreasing prolactin levels leads to a lower diving effort but does not affect breeding success in Adélie penguins</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="32525947" href="https://independent.academia.edu/AkikoKato1">Akiko Kato</a></div><p class="ds-related-work--metadata ds2-5-body-xs">Hormones and Behavior, 2014</p><p class="ds-related-work--abstract ds2-5-body-sm">Current research on seabirds suggests a key role of hormones in the trade-off between self-maintenance and parental investment through their influence on foraging decisions during the breeding period. Although prolactin is known to have major effects on parental care, its role in foraging behavior has rarely been investigated in seabirds to date. The aim of this study was to assess the influence of an experimental decrease in prolactin levels on foraging decisions and its consequences on breeding success in free-living seabirds. To achieve this, we implanted bromocriptine (an inhibitor of prolactin secretion) in male Adélie penguins (Pygoscelis adeliae), monitored their foraging behavior using time-depth recorders over several trips, and recorded their reproductive output. On average 8 ± 0.5 days after implantation, we showed that bromocriptine administration led to an efficient decrease in prolactin levels. However, no differences were seen in foraging trip durations between bromocriptineimplanted birds and controls. Moreover, the time spent diving and the number of dives performed per trip were similar in both groups. By contrast, all diving parameters (including diving efficiency) were negatively affected by the treatment during the first at-sea trip following the treatment. Finally, the treatment did not affect adult body condition or chick growth and survival. Our study highlights the short-term negative effect of low prolactin levels on diving effort, but indicates that a short-term and/or low-magnitude decrease in prolactin levels alone is not sufficient to modify consistently the body maintenance or the parental investment of Adélie penguins.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Decreasing prolactin levels leads to a lower diving effort but does not affect breeding success in Adélie penguins","attachmentId":45715799,"attachmentType":"pdf","work_url":"https://www.academia.edu/13271429/Decreasing_prolactin_levels_leads_to_a_lower_diving_effort_but_does_not_affect_breeding_success_in_Ad%C3%A9lie_penguins","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/13271429/Decreasing_prolactin_levels_leads_to_a_lower_diving_effort_but_does_not_affect_breeding_success_in_Ad%C3%A9lie_penguins"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="4" data-entity-id="5328049" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/5328049/Seasonal_patterns_of_prolactin_and_corticosterone_secretion_in_an_Antarctic_seabird_that_moults_during_reproduction">Seasonal patterns of prolactin and corticosterone secretion in an Antarctic seabird that moults during reproduction</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="7364283" href="https://independent.academia.edu/PhilTrathan">Phil Trathan</a></div><p class="ds-related-work--metadata ds2-5-body-xs">General and Comparative Endocrinology</p><p class="ds-related-work--abstract ds2-5-body-sm">In avian species that have evolved life-history strategies wherein molt and breeding overlap, there are potential conflicts between the regulatory roles of baseline prolactin and corticosterone in parental care (positive) and moult (negative). We describe seasonal patterns of hormonal secretion, moult, and parental behaviour in sibling species of giant petrels (Macronectes spp.) which begin moult during the incubation/early chick-rearing stage of reproduction. With the exception of male Southern giant petrels (Macronectes giganteus), prolactin secretion and moult in Northern (Macronectes halli) and female Southern giant petrels conformed to those observed in all other avian species, with the initiation of moult coincident with decreases from peak prolactin levels. However, male Southern giant petrels began moulting early in incubation when prolactin was increasing and had not yet peaked, which suggests a requirement of prolactin for incubation behaviour and a dissociation of prolactin from moult. Corticosterone showed little seasonal variation and no relationship with moult. When comparing prolactin, corticosterone, and moult in failed vs. active breeders, we found that failed breeding enabled a more rapid down-regulation of prolactin, thus facilitating a more rapid moult. We present specific examples of the behavioural ecology of giant petrels which we conclude help mediate any potential hormonal conflicts between parental care and moult.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Seasonal patterns of prolactin and corticosterone secretion in an Antarctic seabird that moults during reproduction","attachmentId":49341346,"attachmentType":"pdf","work_url":"https://www.academia.edu/5328049/Seasonal_patterns_of_prolactin_and_corticosterone_secretion_in_an_Antarctic_seabird_that_moults_during_reproduction","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/5328049/Seasonal_patterns_of_prolactin_and_corticosterone_secretion_in_an_Antarctic_seabird_that_moults_during_reproduction"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="5" data-entity-id="60915837" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/60915837/Hormonal_correlations_at_transition_from_reproduction_to_molting_in_an_annual_life_cycle_of_Humboldt_penguins_Spheniscus_humboldti_">Hormonal correlations at transition from reproduction to molting in an annual life cycle of Humboldt penguins (Spheniscus humboldti)</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="42242383" href="https://tmd.academia.edu/MasaruWada">Masaru Wada</a></div><p class="ds-related-work--metadata ds2-5-body-xs">General and Comparative Endocrinology, 2004</p><p class="ds-related-work--abstract ds2-5-body-sm">To understand the hormonal mechanism behind a unique strategy of breeding and molting in Humboldt penguins, six pairs of captive Humboldt penguins kept in an outdoor open display pen were observed and blood collected weekly for a year. They all molted between the middle of June and the middle of August within 10 days except one pair that molted about a month later. The late pair had been rearing a hatchling until July due to the successful second clutch after the first clutch failed. A peak of plasma levels of thyroxine and triiodothyronine, respectively, overlapped a period of molting in both sexes. Plasma testosterone concentrations in the males and females were lowest for two month during a period of pre-molt and molting. Plasma concentrations of estradiol were also lowest during the molt in both sexes. Except for the period of molting, sex steroid hormone concentrations were high although there was great individual variation. During the molt, the birds were forced to fast since they did not enter the pool in the display pen where they usually forage live fish. To compensate this forced fasting, they took more food than usual during premolting period and gained body mass to about 20% more than the baseline value. Increased flipper thickness was parallel to increased body mass indicating that the gained body mass attributed to fat reservoir. These data indicate that rapid molting in Humboldt penguins is correlated with a drastic increase and decrease of thyroid hormones during the period of lowest concentrations in sex steroid hormones.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Hormonal correlations at transition from reproduction to molting in an annual life cycle of Humboldt penguins (Spheniscus humboldti)","attachmentId":74151260,"attachmentType":"pdf","work_url":"https://www.academia.edu/60915837/Hormonal_correlations_at_transition_from_reproduction_to_molting_in_an_annual_life_cycle_of_Humboldt_penguins_Spheniscus_humboldti_","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/60915837/Hormonal_correlations_at_transition_from_reproduction_to_molting_in_an_annual_life_cycle_of_Humboldt_penguins_Spheniscus_humboldti_"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="6" data-entity-id="58847039" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/58847039/Kidnapping_of_chicks_in_emperor_penguins_a_hormonal_by_product">Kidnapping of chicks in emperor penguins: a hormonal by-product?</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="42880952" href="https://independent.academia.edu/HerveLormee">Hervé Lormée</a></div><p class="ds-related-work--metadata ds2-5-body-xs">Journal of Experimental Biology, 2006</p><p class="ds-related-work--abstract ds2-5-body-sm">SUMMARY The function and causes of kidnapping juveniles are little understood because individuals sustain some breeding costs to rear an unrelated offspring. Here we focus on the proximal causes of this behaviour in emperor penguins (Aptenodytes forsteri), whose failed breeders often kidnap chicks. We experimentally tested the hypothesis that kidnapping behaviour was the result of high residual levels of prolactin (PRL), a hormone involved in parental behaviour. Penguins with artificially decreased PRL levels by bromocriptine administration kidnapped chicks less often than control penguins. Within the bromocriptine treated group, kidnapping behaviour was not totally suppressed and the probability of kidnapping a chick was positively correlated to PRL levels measured before treatment. During breeding, emperor penguins have to forage in remote ice-free areas. In these birds, PRL secretion is poorly influenced by chick stimuli and has probably evolved to maintain a willingness to retur...</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Kidnapping of chicks in emperor penguins: a hormonal by-product?","attachmentId":73060418,"attachmentType":"pdf","work_url":"https://www.academia.edu/58847039/Kidnapping_of_chicks_in_emperor_penguins_a_hormonal_by_product","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/58847039/Kidnapping_of_chicks_in_emperor_penguins_a_hormonal_by_product"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="7" data-entity-id="13513978" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/13513978/Intra_Clutch_Ratio_of_Yolk_Progesterone_Level_Changes_with_Laying_Date_in_Rockhopper_Penguins_A_Strategy_to_Influence_Brood_Reduction">Intra-Clutch Ratio of Yolk Progesterone Level Changes with Laying Date in Rockhopper Penguins: A Strategy to Influence Brood Reduction?</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="32713025" href="https://antwerp.academia.edu/MarcelEens">Marcel Eens</a></div><p class="ds-related-work--metadata ds2-5-body-xs">PLoS ONE, 2011</p><p class="ds-related-work--abstract ds2-5-body-sm">Hatching asynchrony in avian species generally leads to a size hierarchy among siblings, favouring the first-hatched chicks. Maternally deposited hormones affect the embryo and chick's physiology and behaviour. It has been observed that progesterone, a hormone present at higher levels than other steroid hormones in egg yolks, is negatively related to body mass in embryos, chicks and adults. A differential within-clutch progesterone deposition could therefore be linked to the size hierarchy between siblings and to the resulting brood reduction. We tested whether yolk progesterone levels differed between eggs according to future parental ability to feed the entire clutch in wild rockhopper penguins Eudyptes chrysocome. This species presents a unique reversed egg-size dimorphism and hatching asynchrony, with the larger secondlaid egg (B-egg) hatching before the smaller first-laid egg (A-egg). Yolk progesterone levels increased only slightly with female body mass at laying. However, intra-clutch ratios were not related to female body mass. On the other hand, yolk progesterone levels increased significantly with the date of laying onset for A-eggs while they decreased for B-eggs. Early clutches therefore had proportionally more progesterone in the B-egg compared to the A-egg while late clutches had proportionally less progesterone in the B-egg. We propose that females could strategically regulate yolk progesterone deposition within clutches according to the expected food availability during chick growth, an adaptive strategy to adjust brood reduction to conditions. We also discuss these results, relating to yolk progesterone, in the broader context of other yolk steroids. Citation: Poisbleau M, Demongin L, Parenteau C, Eens M (2011) Intra-Clutch Ratio of Yolk Progesterone Level Changes with Laying Date in Rockhopper Penguins: A Strategy to Influence Brood Reduction? PLoS ONE 6(11): e27765.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Intra-Clutch Ratio of Yolk Progesterone Level Changes with Laying Date in Rockhopper Penguins: A Strategy to Influence Brood Reduction?","attachmentId":45251625,"attachmentType":"pdf","work_url":"https://www.academia.edu/13513978/Intra_Clutch_Ratio_of_Yolk_Progesterone_Level_Changes_with_Laying_Date_in_Rockhopper_Penguins_A_Strategy_to_Influence_Brood_Reduction","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/13513978/Intra_Clutch_Ratio_of_Yolk_Progesterone_Level_Changes_with_Laying_Date_in_Rockhopper_Penguins_A_Strategy_to_Influence_Brood_Reduction"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="8" data-entity-id="104405294" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/104405294/The_breeding_biology_of_erect_crested_penguins_Eudyptes_sclateri_Hormones_behavior_obligate_brood_reduction_and_conservation">The breeding biology of erect-crested penguins, Eudyptes sclateri: Hormones, behavior, obligate brood reduction and conservation</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="43897037" href="https://independent.academia.edu/DavisLloyd">Lloyd Davis</a></div><p class="ds-related-work--metadata ds2-5-body-xs">PLOS ONE</p><p class="ds-related-work--abstract ds2-5-body-sm">Erect-crested penguins are the least studied of all penguins. They breed on two isolated subantarctic island groups, the Antipodes and Bounty Islands. Sporadic nest counts indicate a dramatic decline in numbers of erect-crested penguins over the last 50 years. Here we present data from a study undertaken in 1998 on the breeding biology, behavior and hormones of erect-crested penguins. It represents, even today, by far the most detailed data available on this species. The penguins exhibited extreme reversed egg-size dimorphism, whereby the first-laid A-egg was much smaller than the second-laid B-egg. A-eggs were lost before (42.3%) or on (37.8%) the day the B-egg was laid, and none survived more than 7 days after that. The penguins were in a low state of reproductive readiness, as evidenced by low levels of copulation, fighting, and testosterone in males during the courtship/laying period when, curiously, plasma levels of testosterone were at least as high in females. The laying inte...</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"The breeding biology of erect-crested penguins, Eudyptes sclateri: Hormones, behavior, obligate brood reduction and conservation","attachmentId":104144497,"attachmentType":"pdf","work_url":"https://www.academia.edu/104405294/The_breeding_biology_of_erect_crested_penguins_Eudyptes_sclateri_Hormones_behavior_obligate_brood_reduction_and_conservation","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/104405294/The_breeding_biology_of_erect_crested_penguins_Eudyptes_sclateri_Hormones_behavior_obligate_brood_reduction_and_conservation"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="9" data-entity-id="57684214" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/57684214/Sex_Steroid_and_Corticosterone_Levels_of_Ad%C3%A9lie_Penguins_Pygoscelis_adeliae_during_Courtship_and_Incubation">Sex Steroid and Corticosterone Levels of Adélie Penguins ( Pygoscelis adeliae) during Courtship and Incubation</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="43897037" href="https://independent.academia.edu/DavisLloyd">Lloyd Davis</a></div><p class="ds-related-work--metadata ds2-5-body-xs">General and Comparative Endocrinology, 1999</p><p class="ds-related-work--abstract ds2-5-body-sm">Plasma levels of sex steroids (progesterone, 17␣hydroxyprogesterone, total androgens, and estradiol) were measured at six stages from courtship to late incubation in Adélie penguins. The pattern of change detected in the levels of plasma total androgens (males) and estradiol (females) was consistent with that found in many birds, with elevated levels during courtship (total androgens, 4 ng/ml; estradiol, 0.5 ng/ml) declining to low, stable levels during incubation. Progesterone levels declined moderately from 1.3 to 0.75-1.0 ng/ml in females following egg laying, but levels of 0.8-1.2 ng/ml persisted in males throughout the study period. 17␣-Hydroxyprogesterone levels were consistently low (approximately 0.2 ng/ml) in females but progressively declined in males from 0.75 during courtship to F0.3 ng/ml at egg laying and during foraging. Plasma corticosterone levels were measured over the same period and were elevated in both males and females at courtship (16-18 ng/ml) and while fasting on the nest (11-15 ng/ml), but had declined in birds returning from foraging at sea, suggesting that elevated levels are related to the metabolic demands of fasting. 1999 Academic Press</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Sex Steroid and Corticosterone Levels of Adélie Penguins ( Pygoscelis adeliae) during Courtship and Incubation","attachmentId":72465228,"attachmentType":"pdf","work_url":"https://www.academia.edu/57684214/Sex_Steroid_and_Corticosterone_Levels_of_Ad%C3%A9lie_Penguins_Pygoscelis_adeliae_during_Courtship_and_Incubation","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/57684214/Sex_Steroid_and_Corticosterone_Levels_of_Ad%C3%A9lie_Penguins_Pygoscelis_adeliae_during_Courtship_and_Incubation"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div></div></div><div class="ds-sticky-ctas--wrapper js-loswp-sticky-ctas hidden"><div class="ds-sticky-ctas--grid-container"><div class="ds-sticky-ctas--container"><button class="ds2-5-button js-swp-download-button" data-signup-modal="{"location":"continue-reading-button--sticky-ctas","attachmentId":39260550,"attachmentType":"pdf","workUrl":null}">See full PDF</button><button class="ds2-5-button ds2-5-button--secondary js-swp-download-button" data-signup-modal="{"location":"download-pdf-button--sticky-ctas","attachmentId":39260550,"attachmentType":"pdf","workUrl":null}"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">download</span>Download PDF</button></div></div></div><div class="ds-below-fold--grid-container"><div class="ds-work--container js-loswp-embedded-document"><div class="attachment_preview" data-attachment="Attachment_39260550" style="display: none"><div class="js-scribd-document-container"><div class="scribd--document-loading js-scribd-document-loader" style="display: block;"><img alt="Loading..." src="//a.academia-assets.com/images/loaders/paper-load.gif" /><p>Loading Preview</p></div></div><div style="text-align: center;"><div class="scribd--no-preview-alert js-preview-unavailable"><p>Sorry, preview is currently unavailable. 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