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Relationship between reproductive hormones and migration distance in a polygynous songbird, the Red-winged Blackbird (Agelaius phoeniceus)

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Abstract

Many bird species migrate to southern overwintering locations to avoid harsh conditions at their breeding grounds, but at the cost of an energetically demanding migration that may delay their spring reproductive development. Previous work on the relationship between migration distance and reproductive readiness has primarily focused on early season baseline testosterone in both males and females. However, for females, testosterone alone may not be the appropriate measurement of reproductive development. Estradiol, a metabolite of testosterone that is essential for breeding behaviors and reproduction, should also be measured. Furthermore, baseline testosterone varies throughout the day and may change due to social interactions that occurred prior to sampling. Injection of gonadotropin-releasing hormone (GnRH) elicits an individual’s maximum potential testosterone production, minimizing daily and social variation. We explored relationships between migration distance and reproductive status after arrival to the breeding ground in Red-winged Blackbirds (Agelaius phoeniceus). We predicted that individuals that travel a shorter distance will have higher levels of reproductive hormones upon arrival given they are able to invest less in migration and more in reproduction. This is important because individuals that breed earlier often have higher reproductive success. In females, we measured baseline estradiol and testosterone. In males, we assessed baseline and GnRH-induced testosterone. Hormone values were related to migration distance, estimated by stable isotope analysis of claw samples collected before breeding began in eastern North Dakota. We found that males with shorter inferred migration distances have higher baseline testosterone upon arrival. However, inferred migration distance was not correlated with GnRH-induced testosterone. Female inferred migration distance was not correlated with baseline testosterone, but it was correlated with baseline estradiol. Females with higher testosterone had lower estradiol, suggesting that testosterone in females is not a reliable indicator of estradiol levels, thus readiness to breed. Our observations suggest that baseline hormone levels were related to migration distance, but baseline testosterone alone may not provide a complete assessment of a male or female’s preparedness to breed following spring migration.

Zusammenfassung

Beziehung zwischen Fortpflanzungshormonen und Zugstrecke bei einem polygynen Singvogel, dem Rotflügelstärling (Agelaius phoeniceus).

Viele Vogelarten ziehen in südliche Überwinterungsgebiete, um den rauhen Bedingungen in ihren Brutgebieten zu entgehen, allerdings um den Preis eines energieaufwendigen Zuges, der ihre Fortpflanzung im Frühjahr verzögern kann. Frühere Arbeiten über den Zusammenhang zwischen Zugstrecke und Fortpflanzungsbereitschaft konzentrierten sich in erster Linie auf den Testosteron-Basiswert von Männchen und Weibchen zu Beginn der Saison. Aber bei Weibchen ist Testosteron allein möglicherweise nicht das geeignete Maß für die Entwicklung der Fortpflanzung. Östradiol, ein Testosteron-Metabolit, der für das Brutverhalten und die Fortpflanzung wichtig ist, sollte ebenfalls gemessen werden. Außerdem schwankt der Testosteron-Basiswert im Laufe des Tages und kann sich aufgrund von sozialen Interaktionen kurz vor der Probenentnahme ändern. Durch die Injektion von Gonadotropin-Releasing-Hormon (GnRH) wird die für ein Einzeltier maximal mögliche Testosteronproduktion ausgelöst, wobei die täglichen und sozialen Schwankungen minimiert werden. Wir untersuchten den Zusammenhang zwischen der Zugstrecke und dem Fortpflanzungsstatus vom Rotflügelstärling (Agelaius phoeniceus) nach der Ankunft im Brutgebiet und sagten voraus, dass Individuen, die eine kürzere Strecke zurücklegen, bei ihrer Ankunft einen höheren Gehalt an Fortpflanzungshormonen aufweisen, da sie weniger in den Zug und mehr in die Fortpflanzung investieren können. Dies ist deshalb wichtig, weil Tiere, die sich früher fortpflanzen, oft einen höheren Fortpflanzungserfolg haben. Bei den Weibchen bestimmten wir den Basiswert von Östradiol und Testosteron, bei den Männchen den Basiswert und das GnRH-induzierte Testosteron. Die Hormonwerte wurden zur Zugstrecke in Relation gesetzt, die anhand der Analyse stabiler Isotope von Krallenproben, gesammelt vor dem Brutbeginn im östlichen North Dakota, geschätzt wurde. Wir stellen fest, dass der Basiswert des Testosterons bei Männchen mit kürzeren Zugstrecken bei der Ankunft auf einem höheren Niveau lag. Aber die ermittelte Zugstrecke korrelierte nicht mit dem GnRH-induzierten Testosteron. Bei den Weibchen korrelierte die Zugstrecke nicht mit dem Testosteron-Basiswert, wohl aber mit dem Basiswert des Östradiols. Weibchen mit einem höheren Testosteronspiegel wiesen einen niedrigeren Östradiolspiegel auf, was darauf hindeutet, dass Testosteron bei weiblichen Tieren kein zuverlässiger Indikator für den Östradiolspiegel und damit für die Bereitschaft zur Fortpflanzung ist. Unsere Ergebnisse deuten darauf hin, dass die Hormon-Basiswerte mit der Zugstrecke zusammenhängen, der Testosteron-Basiswert allein aber vermutlich keinen vollständigen Aufschluss über die Brutbereitschaft eines Männchens oder Weibchens direkt nach dem Frühjahrszug gibt.

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References

  • Adkins-Regan E (2005) Hormones and animal social behavior. Princeton University Press, Princeton

    Google Scholar 

  • Apfelbeck B, Goymann W (2011) Ignoring the challenge? Male Black Redstarts (Phoenicurus ochruros) do not increase testosterone levels during territorial conflicts but they do so in response to gonadotropin-releasing hormone. Proc R Soc B Biol Sci 278:3233–3242

    Article  CAS  Google Scholar 

  • Ball GF, Ketterson ED (2008) Sex differences in the response to environmental cues regulating seasonal reproduction in birds. Philos Trans R Soc B Biol Sci 363:231–246

    Article  Google Scholar 

  • Bearhop S, Furness RW, Hilton GM, Votier SC (2003) A forensic approach to understanding diet and habitat use from stable isotope analysis of (avian) claw material. Funct Ecol 17:270–275

    Article  Google Scholar 

  • Beletsky LD, Orians GH, Wingfield JC (1989) Relationships of steroid hormones and polygyny to territorial status, breeding experience, and reproductive success in male Red-winged Blackbirds. Auk 106:107–117

    Article  Google Scholar 

  • Beletsky LD, Orians GH, Wingfield JC (1992) Year-to-year patterns of circulating levels of testosterone and corticosterone in relation to breeding density, experience, and reproductive success of the polygynous Red-winged Blackbird. Horm Behav 26:420–432

    Article  CAS  PubMed  Google Scholar 

  • Butler CJ (2003) The disproportionate effect of global warming on the arrival dates of short distance migratory birds in North America. Ibis (lond 1859) 145:484–495

    Article  Google Scholar 

  • Caro SP (2012) Avian ecologists and physiologists have different sexual preferences. Gen Comp Endocrinol 176:1–8

    Article  CAS  PubMed  Google Scholar 

  • Caro SP, Charmantier A, Lambrechts MM et al (2009) Local adaptation of timing of reproduction: females are in the driver’s seat. Funct Ecol 23:172–179

    Article  Google Scholar 

  • Covino KM, Jawor JM, Kelly JF, Moore FR (2017) Overlapping life-history stages in migrating songbirds: variation in circulating testosterone and testosterone production capacity. J Ornithol 158:203–212

    Article  Google Scholar 

  • Covino KM, Jawor JM, Morris SR, Moore FR (2018) Sex-specific hypothalamic-pituitary gonadal axis sensitivity in migrating songbirds. Horm Behav 97:112–120

    Article  CAS  PubMed  Google Scholar 

  • Cristol DA, Johnsen TS (1994) Spring arrival, aggression and testosterone in female Red-winged Blackbirds (Agelaius phoeniceus). Auk 111:210–214

    Article  Google Scholar 

  • Cristol DA, Baker MB, Carbone C (1999) Differential migration revisited. Latitudinal segregation by age and sex class. In: Nolan Jr V, Ketterson ED, Thompson CF (eds) Current ornithology, vol 15. Kluwer, New York, pp 33–88

    Chapter  Google Scholar 

  • Dale CA, Leonard ML (2011) Reproductive consequences of migration decisions by Ipswich Sparrows (Passerculus sandwichensis princeps). Can J Zool 89:100–108

    Article  Google Scholar 

  • Deviche P, Gao S, Davies S et al (2012) Rapid stress-induced inhibition of plasma testosterone in free-ranging male rufous-winged sparrows, Peucaea carpalis: characterization, time course, and recovery. Gen Comp Endocrinol 177:1–8

    Article  CAS  PubMed  Google Scholar 

  • Devries SM, Holbrook AL, Winters CP, Jawor JM (2011) Non-breeding gonadal testosterone production of male and female Northern Cardinals (Cardinalis cardinalis) following GnRH challenge. Gen Comp Endocrinol 174:370–378

    Article  CAS  PubMed  Google Scholar 

  • Dolbeer RA (1982) Migration patterns for age and sex classes of blackbirds and starlings. J Field Ornithol 53:28–46

    Google Scholar 

  • Duff JP, Holliman A, Hateley G et al (2011) Wildlife disease: water bird mortality associated with freezing winter weather and disease. Vet Rec 168:593

    Article  CAS  PubMed  Google Scholar 

  • Enstrom DA, Ketterson ED, Nolan V (1997) Testosterone and mate choice in the Dark-eyed Junco. Anim Behav 54:1135–1146

    Article  Google Scholar 

  • Finch T, Butler SJ, Franco AMA, Cresswell W (2017) Low migratory connectivity is common in long-distance migrant birds. J Anim Ecol 86:662–673

    Article  PubMed  Google Scholar 

  • Fudickar AM, Ketterson ED (2018) Genomes to space stations: the need for the integrative study of migration for avian conservation. Biol Lett 14:20170741

    Article  PubMed  PubMed Central  Google Scholar 

  • Fudickar AM, Greives TJ, Atwell JW et al (2016) Reproductive allochrony in seasonally sympatric populations maintained by differential response to photoperiod: implications for population divergence and response to climate change. Am Nat 187:436–446

    Article  PubMed  Google Scholar 

  • Gagnon C, Hobson KA (2009) Using stable isotopes to track frugivory in migratory passerines. Can J Zool 87:981–992

    Article  CAS  Google Scholar 

  • Goymann W, Wingfield JC (2014) Male-to-female testosterone ratios, dimorphism, and life history—what does it really tell us? Behav Ecol 25:685–699

    Article  Google Scholar 

  • Goymann W, Moore IT, Oliveira RF (2019) Challenge hypothesis 2.0: a fresh look at an established idea. Bioscience 69:432–442

    Article  Google Scholar 

  • Graham JL, Needham KB, Bertucci EM et al (2019) Onset of daily activity in a female songbirdis related to peak-induced estradiol levels. Integr Comp Biol 59:1059–1067

    Article  CAS  PubMed  Google Scholar 

  • Guchhait P, Haldar C (1999) Circadian rhythms of melatonin and sex steroids in a nocturnal bird, Indian Spotted Owlet Athene brama during reproductively active and inactive phases. Biol Rhythm Res 30:508–516

    Article  CAS  Google Scholar 

  • Hobson KA (1999) Tracing origins and migration of wildlife using stable isotopes: a review. Oecologia 120:314–326

    Article  PubMed  Google Scholar 

  • Hobson KA, Van Wilgenburg SL, Faaborg J et al (2014) Connecting breeding and wintering grounds of neotropical migrant songbirds using stable hydrogen isotopes: a call for anisotopic atlas of migratory connectivity. J Field Ornithol 85:237–257

    Article  Google Scholar 

  • Jawor JM, McGlothlin JW, Casto JM et al (2006) Seasonal and individual variation in response to GnRH challenge in male Dark-eyed Juncos (Junco hyemalis). Gen Comp Endocrinol 149:182–189

    Article  CAS  PubMed  Google Scholar 

  • Kelly TR, MacGillivray HL, Sarquis-Adamson Y et al (2016) Seasonal migration distance varies with natal dispersal and predicts parasitic infection in Song Sparrows. Behav Ecol Sociobiol 70:1857–1866

    Article  Google Scholar 

  • Ketterson ED, Nolan V (1976) Geographic variation and its climatic correlates in the sex ratio of eastern-wintering Dark-eyed Juncos (Junco hyemalis hyemalis). Ecology 57:679–693

    Article  Google Scholar 

  • Ketterson ED, Nolan VJ (1983) The evolution of differential bird migration. In: Johnson RF (ed) Current ornithology. Kluwer Academic, New York, pp 357–402

    Chapter  Google Scholar 

  • Ketterson ED, Nolan V, Sandell M (2005) Testosterone in females: mediator of adaptive traits, constraint on sexual dimorphism, or both? Am Nat 166:85–98

    Article  Google Scholar 

  • Kimmitt AA (2020) Females as the gatekeepers to seasonal breeding: what we can learn by studying reproductive mechanisms in both sexes. Integr Comp Biol 60:703–711

    Article  PubMed  Google Scholar 

  • Lymburner AH, Kelly TR, Hobson KA et al (2016) Testosterone, migration distance, and migratory timing in Song Sparrows Melospiza melodia. Horm Behav 85:102–107

    Article  CAS  PubMed  Google Scholar 

  • Marra PP, Cohen EB, Loss SR et al (2015) A call for full annual cycle research in animal ecology. Biol Lett 11:20150552

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  • Martin TE (1995) Avian life history evolution in relation to nest sites, nest predation, and food. Ecol Monogr 65:101–127

    Article  Google Scholar 

  • Mazerolle DF, Hobson KA (2005) Estimating origins of short-distance migrant songbirds in North America: contrasting inferences from hydrogen isotope measurements of feathers, claws, and blood. Condor 107:280–288

    Article  Google Scholar 

  • McGlothlin JW, Jawor JM, Greives TJ et al (2008) Hormones and honest signals: males with larger ornaments elevate testosterone more when challenged. J Evol Biol 21:39–48

    Article  CAS  PubMed  Google Scholar 

  • Muma KE (1986) Seasonal changes in the hour of oviposition by Red-winged Blackbirds in southwestern Ontario. J F Ornithol 57:228–229

    Google Scholar 

  • Needham KB, Dochtermann NA, Greives TJ (2017) Consistent individual variation in day, night, and GnRH-induced testosterone concentrations in House Sparrows (Passer domesticus). Gen Comp Endocrinol 246:211–217

    Article  CAS  PubMed  Google Scholar 

  • Newton I, Dale LC (1996) Bird migration at different latitudes in eastern North America. Auk 113:626–635

    Article  Google Scholar 

  • Orians GH, Willson MF (1964) Interspecific territories of birds. Ecology 45:736–745

    Article  Google Scholar 

  • Pärn H, Lindström KM, Sandell M, Amundsen T (2008) Female aggressive response and hormonal correlates—an intrusion experiment in a free-living passerine. Behav Ecol Sociobiol 62:1665–1677

    Article  Google Scholar 

  • R Core Team (2018) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. Retrieved from https://cran.r-project.org/

  • Ramenofsky M, Cornelius JM, Helm B (2012) Physiological and behavioral responses of migrants to environmental cues. J Ornithol 153:181–191

    Article  Google Scholar 

  • Remage-Healey L, Coleman MJ, Oyama RK, Schlinger BA (2010) Brain estrogens rapidly strengthen auditory encoding and guide song preference in a songbird. Proc Natl AcadSci USA 107:3852–3857

    Article  CAS  Google Scholar 

  • Robbins CS, Bruun B, Zim HS (2014) Birds of North America: a guide to field identification. St. Martin’s Press, New York

    Google Scholar 

  • Ronald KL, Zeng R, White DJ et al (2017) What makes a multimodal signal attractive? A preference function approach. Behav Ecol 28:677–687

    Article  Google Scholar 

  • Rosenberg KV, Dokter AM, Blancher PJ et al (2019) Decline of the North American avifauna. Science 366:120–124

    Article  CAS  PubMed  Google Scholar 

  • Rosvall KA (2013a) Life history trade-offs and behavioral sensitivity to testosterone: an experimental test when female aggression and maternal care co-occur. PLoS ONE 8:1–9

    Article  CAS  Google Scholar 

  • Rosvall KA (2013b) Proximate perspectives on the evolution of female aggression: good for the gander, good for the goose. Philos Trans R Soc B Biol Sci 368:20130083

    Article  Google Scholar 

  • Rosvall KA, Burns CMB, Hahn TP, Ketterson ED (2013) Sources of variation in HPG axis reactivity and individually consistent elevation of sex steroids in a female songbird. Gen Comp Endocrinol 194:230–239

    Article  CAS  PubMed  Google Scholar 

  • Rushing CS, Dudash MR, Studds CE, Marra PP (2015) Annual variation in long-distance dispersal driven by breeding and non-breeding season climatic conditions in a migratory bird. Ecography 38:1006–1014

    Article  Google Scholar 

  • Sawin RS, Lutman MW, Linz GM, Bleier WJ (2003) Predators on Red-winged Blackbird nests in eastern North Dakota. J Field Ornithol 74:288–292

    Article  Google Scholar 

  • Searcy WA, Capp MS (1997) Estradiol dosage and the solicitation display assay in Red-winged Blackbirds. Condor 99:826–828

    Article  Google Scholar 

  • Shansky RM (2019) Are hormones a “female problem” for animal research? Science 364:825–826

    Article  CAS  PubMed  Google Scholar 

  • Singh D, Montoure J, Ketterson ED (2021) Exposure to artificial light at night accelerates but does not override latitude-dependent seasonal reproductive response in Dark-eyed Juncos. Environ Pollut 279:116867

    Article  CAS  PubMed  Google Scholar 

  • Smith FA, Betancourt JL, Brown JH (1995) Evolution of body size in the Woodrat over the past 25,000 years of climate change. Science 270:2012–2014

    Article  CAS  Google Scholar 

  • Stonefish D, Eshleman MA, Linz GM, Homan HJ, Klug PE, Greives TJ, Gillam EH (2021) Migration routes and wintering areas of male Red-winged Blackbirds as determined using geolocators. J Field Ornithol (In press)

  • Taylor H (1974) The application of oxygen and hydrogen isotope studies to problems of hydrothermal, alteration and ore deposition. Econ Geol 69:843–883

    Article  CAS  Google Scholar 

  • Tonra CM, Marra PP, Holberton RL (2011) Early elevation of testosterone advances migratory preparation in a songbird. J Exp Biol 214:2761–2767

    Article  CAS  PubMed  Google Scholar 

  • Tonra CM, Marra PP, Holberton RL (2013) Experimental and observational studies of seasonal interactions between overlapping life history stages in a migratory bird. Horm Behav 64:825–832

    Article  CAS  PubMed  Google Scholar 

  • Verhulst S, Nilsson JÅ (2008) The timing of birds’ breeding seasons: a review of experiments that manipulated timing of breeding. Philos Trans R Soc B Biol Sci 363:399–410

    Article  Google Scholar 

  • Visser ME, Perdeck AC, van Balen JH, Both C (2009) Climate change leads to decreasing bird migration distances. Glob Change Biol 15:1859–1865

    Article  Google Scholar 

  • Voigt C, Leitner S (2013) Testosterone-dependency of male solo song in a duetting songbird—evidence from females. Horm Behav 63:122–127

    Article  CAS  PubMed  Google Scholar 

  • Wassenaar LI, Hobson KA (2003) Comparative equilibration and online technique for determination of non-exchangeable hydrogen of keratins for use in animal migration studies. Isotopes Environ Health Stud 39:211–217

    Article  CAS  PubMed  Google Scholar 

  • Werner SJ, Hobson KA, Van Wilgenburg SL, Fischer JW (2016) Multi-isotopic (δ2H, δ13C, δ15N) tracing of molt origin for red-winged blackbirds associated with agro-ecosystems. PLoS ONE 11:1–22

    Article  Google Scholar 

  • Wilcoxen TE, Horn DJ, Hogan BM et al (2015) Effects of bird-feeding activities on the health of wild birds. Conserv Physiol 3:1–13

    Article  CAS  Google Scholar 

  • Williams TD, Kitaysky AS, Vézina F (2004) Individual variation in plasma estradiol-17b and androgen levels during egg formation in the European Starling Sturnus vulgaris: implications for regulation of yolk steroids. Gen Comp Endocrinol 136:346–352

    Article  CAS  PubMed  Google Scholar 

  • Wingfield JC (1985) Short-term changes in plasma levels of hormones during establishment and defense of a breeding territory in male Song Sparrows, Melospiza melodia. Horm Behav 19:174–187

    Article  CAS  PubMed  Google Scholar 

  • Wingfield JC, Hegner RE, Dufty AM, Ball GF (1990) The “challenge hypothesis’’: theoretical implications for patterns of testosterone secretion, mating systems, and breeding strategies. Am Nat 136:829–846

    Article  Google Scholar 

  • Wingfield JC, Lynn SE, Soma KK (2001) Avoiding the ‘costs’ testosterone: ecological bases of hormone–behavior interactions. Brain Behav Evol 57:239–251

    Article  CAS  PubMed  Google Scholar 

  • Wingfield JC, Ball GF, Dufty AM et al (2011) Testosterone and aggression in birds. Am Sci 75:602–608

    Google Scholar 

  • Yasukawa K, Searcy WA (2019) Red-winged Blackbird (Agelaius phoeniceus). In: Birds North Am. https://birdsna-org.ezproxy.lib.ndsu.nodak.edu/SpeciesAccount/bna/species/rewbla/. Accessed 25 Jan 2020

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Acknowledgements

We would like to thank S. Grillo, B. Weber, M. Cremers, and K. Adkins for getting up at 4:00 am and spending countless hours in the wetlands of North Dakota chasing blackbirds. We are also grateful for the members of ‘Team Bird’ at NDSU. They have been there for technical and emotion support throughout this project. Drs. S. DeKeyser and G. Linz provided invaluable feedback during the planning of this study. We owe thanks to K. Tompkins and T. Gwilliams at the U.S. Fish and Wildlife Service in Valley City for allowing us to work at the Alice Waterfowl Production Area.

Funding

Funding for this project was provided by the Biological Sciences Department at North Dakota State University and the United States Department of Agriculture (USDA), Animal and Plant Health Inspection Service (APHIS), Wildlife Services (WS), and National Wildlife Research Center.

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Authors and Affiliations

  1. Department of Biological Sciences, North Dakota State University, Fargo, ND, 58102, USA

    Michelle A. Eshleman, Esther Morales-Vega & Timothy J. Greives

  2. United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center, North Dakota State University, Department of Biological Sciences, Fargo, ND, 58102, USA

    Page E. Klug

  3. Institute of Environmental Change and Society, University of Regina, Regina, SK, S4S 0A2, Canada

    Björn Wissel

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  1. Michelle A. Eshleman
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  2. Page E. Klug
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  5. Timothy J. Greives
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Contributions

ME, TG, and PK contributed to the experimental design and data analysis. ME, EM-V, and TG conducted the field work. BW analyzed stable isotopes in claw samples. All authors contributed to the writing of this manuscript.

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Correspondence to Page E. Klug.

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The data collected on this project was approved by the North Dakota State University Institutional Animal Care and Use Committee, North Dakota Game and Fish Department, the United States Geological Survey Bird Banding Laboratory, the US Fish and Wildlife Service in Valley City, and the USDA-APHIS-WS NWRC. Experiments comply with the current laws of the country in which they were performed.

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Eshleman, M.A., Klug, P.E., Morales-Vega, E. et al. Relationship between reproductive hormones and migration distance in a polygynous songbird, the Red-winged Blackbird (Agelaius phoeniceus). J Ornithol 163, 425–436 (2022). https://doi.org/10.1007/s10336-021-01940-7

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