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Prey size and nestling gape size affect allocation within broods of the Mountain Bluebird

  • Jordyn A. Stalwick
  • Karen L. Wiebe
Original Article

Abstract

The allocation of prey within broods of altricial nestlings may be the result of parents targeting certain offspring preferentially and/or the result of intrabrood competition related to features of nestlings such as body size. We investigated two mechanisms that could influence allocation of food within broods of Mountain Bluebirds (Sialia currucoides) by filming the size and type of prey that parents fed nestlings. According to the gape size constraint hypothesis, the inability of small nestlings to physically swallow large prey items might place junior brood members at a higher risk of starvation than older siblings if parents do not bring enough small items. Consistent with this idea, the frequency of ‘testing’, placing an item in the gape of a nestling but then withdrawing it, was positively correlated with prey size. The junior nestling of a brood was fed less often when parents brought larger prey items, and nestlings were tested more in the early nestling stage (0–4 days old) when their gapes were smaller than at older stages. Parents of many cavity-nesting species may feed the brood from the nest entrance and the resulting scramble competition among brood members to access the entrance hole also potentially increases the mortality of the least competitive (smallest) nestlings. Although the frequency of feeding from the entrance hole was prevalent during the late nestling stage (≥ 12 days old), feeding from the entrance was not associated with mortality rate in bluebird broods and the mortality of junior nestlings was not linked to the testing of prey. The results confirm that a mechanism of gape size constraint does direct large prey away from junior nestlings, but apparently small-sized prey items were abundant enough during our study so that this did not result in increased mortality of nestlings.

Keywords

Prey allocation Gape size constraint hypothesis Hatching asynchrony 

Zusammenfassung

Die Größe der Nahrung und der Schnabelöffnung beim Sperren beeinflussen beim Berghüttensänger die Verteilung der Nahrung auf die Brut.

Bei Nesthockern könnte die Verteilung des Futters auf die Nestlinge davon abhängen, ob Elterntiere einzelne Jungen bevorzugen. Sie könnte aber auch an der Konkurrenzsituation zwischen den Jungen liegen, die mit Eigenschaften wie z.B. der Körpergröße eines Nestlings zusammenhängt. Wir untersuchten zwei mögliche Mechanismen, die beim Berghüttensänger (Sialia currucoides) bei der Verteilung des Futters an einzelne Nestlinge eine Rolle spielen könnten. Hierfür filmten wir die Größe und Art der Beute, die die Elterntiere an die Nestlinge verfütterten. Entsprechend der „gape-size constraint hypothesis“(Hypothese der Schnabelöffnungs-Größe als einschränkendem Faktor) könnte die rein physikalische Unfähigkeit kleiner Nestlinge, größere Futterbrocken hinunterzuschlucken, für die jüngeren Nestlinge gegenüber ihren älteren Geschwistern ein größeres Risiko zu verhungern bedeuten, wenn die Eltern nicht auch ausreichend viele kleinere Nahrungsstücke beibringen. Im Einklang mit dieser Theorie korrelierte die „Test-Frequenz“, mit der ein Stückchen Futter in den aufgesperrten Schnabel eines Nestlings gelegt und wieder herausgezogen wurde, positiv mit der Größe der Stückchen. Innerhalb einer Brut erhielten die jüngeren Nestlinge seltener Nahrung, wenn die Eltern größere Nahrungsbrocken herantrugen, und die Nestlinge wurden öfter im frühen Nestlingsstadium (0–4 Tage alt) getestet, als ihre Schnäbel noch kleiner als in den späteren Stadien waren. Bei vielen Höhlenbrütern füttern die Eltern ihre Brut vermutlich vom Höhleneingang her, und das dabei entstehende Gedränge und die damit verbundene Konkurrenzsituation unter den Geschwistern, möglichst nahe an das Einflugloch zu kommen, würde potentiell die Sterblichkeitsrate unter den wettbewerbschwächsten (kleinsten) Nestlingen erhöhen. Obwohl die Häufigkeit des Fütterns vom Einflugloch her im späteren Stadium (> 12 Tage alt) vorherrschte, gab es aber keinen Zusammenhang mit der Mortalitätsrate der Berghüttensänger-Jungen, und die Sterblichkeitsrate der jungen Nestlinge hing nicht mit dem Nahrungsstückchen-Test zusammen. Diese Ergebnisse bestätigen, dass aufgrund der Einschränkung durch die Größe der Schnabelöffnung größere Futterbrocken in der Tat nicht bei den jüngeren Nestlinge ankommen, dass es aber während unserer Untersuchung offenbar ausreichend viele kleinere Nahrungsbrocken gab, so dass die größeren Brocken zu keiner höheren Sterblichkeitsrate bei den Nestlingen führte.

Notes

Acknowledgements

Thanks to the Scherrers, Arendals and Bridge Creek Ranch for access to their properties. S. Srayko helped with insect identification. The study was funded by a Natural Sciences and Engineering Research Council of Canada grant (203177) to K. L. W. This study complied with the current laws of Canada.

Compliance with ethical standards

Ethical approval

All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in the studies involving animals were in accordance with the ethical standards of the institution and conducted under Animal Care Permit 20160018.

References

  1. Budden AE, Beissinger SR (2009) Resource allocation varies with parental sex and brood size in the asynchronously hatching Green-rumped Parrotlet (Forpus passerinus). Behav Ecol Sociobiol 63:637–647CrossRefGoogle Scholar
  2. Clark AB (1995) Gapes of sexually dimorphic blackbird nestlings do not show sexually dimorphic growth. Auk 112:364–374CrossRefGoogle Scholar
  3. Dickens M, Hartley IR (2007) Differences in parental food allocation rules: evidence for sexual conflict in the Blue Tit? Behav Ecol 18:674–679CrossRefGoogle Scholar
  4. Dickens M, Berridge D, Hartley IR (2008) Biparental care and offspring begging strategies: hungry nestling Blue Tits move towards the father. Anim Behav 75:167–174CrossRefGoogle Scholar
  5. Fox J, Weisberg S (2011) An {R} companion to applied regression, 2nd edn. Sage, Thousand Oaks. http://socserv.socsci.mcmaster.ca/jfox/Books/Companion. Accessed 12 July 2017
  6. García-Navas V, Ferrer ES, Jose Sanz J (2012) Prey selectivity and parental feeding rates of Blue Tits Cyanistes caeruleus in relation to nestling age. Bird Study 59:236–242CrossRefGoogle Scholar
  7. García-Navas V, Ferrer ES, Serrano-Davies E (2014) Experimental evidence for parental, but not parentally biased, favouritism in relation to offspring size in Blue Tits Cyanistes caeruleus. Ibis 156:404–414CrossRefGoogle Scholar
  8. Gil D, Bulmer E, Celis P, López-Rull I (2008) Adaptive developmental plasticity in growing nestlings: sibling competition induces differential gape growth. Proc R Soc B-Biol Sci 275:549–554CrossRefGoogle Scholar
  9. Glassey B, Forbes S (2003) Why Brown-headed Cowbirds do not influence Red-winged Blackbird parent behaviour. Anim Behav 65:1235–1246CrossRefGoogle Scholar
  10. Granbom M, Smith HG (2006) Food limitation during breeding in a heterogeneous landscape. Auk 123:97–107CrossRefGoogle Scholar
  11. Herlugson CJ (1982) Food of adult and nestling Western and Mountain Bluebirds. Murrelet 63:59–65CrossRefGoogle Scholar
  12. Johnson LS, Dawson RD (2018) Mountain Bluebird (Sialia currucoides), version 2.0. In: Rodewald PG (ed) The birds of North America. Cornell Lab of Ornithology, IthacaGoogle Scholar
  13. Johnson LS, Hebert RM, Napolillo FM, Allen A (2013a) The process of fledging in the Mountain Bluebird. J Field Ornithol 84:367–376CrossRefGoogle Scholar
  14. Johnson LS, Napolillo FM, Kozlovsky DY, Hebert RM, Allen A (2013b) Variation in incubation effort during egg laying in the Mountain Bluebirds and its association with hatching asynchrony. J Field Ornithol 84:242–254CrossRefGoogle Scholar
  15. Kacelnik A, Cotton PA, Stirling L, Wright J (1995) Food allocation among nestling starlings: sibling competition and the scope of parental choice. Proc R Soc B-Biol Sci 259:259–263CrossRefGoogle Scholar
  16. Kim M, Furness RW, Nager RG (2010) Hatching asynchrony is constrained by parental nest attendance during laying. Behav Ecol Sociobiol 64:1087–1097CrossRefGoogle Scholar
  17. Kuznetsova A, Brockhoff PB, Christensen RHB (2017) lmerTest package: tests in linear mixed effects models. J Stat Softw 82:1–26CrossRefGoogle Scholar
  18. Labocha MK, Hayes JP (2012) Morphometric indices of body condition in birds: a review. J Ornithol 153:1–22CrossRefGoogle Scholar
  19. Leonard M, Horn A (1996) Provisioning rules in Tree Swallows. Behav Ecol Sociobiol 38:341–347CrossRefGoogle Scholar
  20. Maddox JD, Weatherhead PJ (2008) Egg size variation in birds with asynchronous hatching: is bigger really better? Am Nat 171:358–365CrossRefGoogle Scholar
  21. Magrath RD (1990) Hatching asynchrony in altricial birds. Biol Rev Camb Philos 65:587–622CrossRefGoogle Scholar
  22. Mainwaring MC, Lucy D, Hartley IR (2011) Parentally biased favouritism in relation to offspring sex in Zebra Finches. Behav Ecol Sociobiol 65:2261–2268CrossRefGoogle Scholar
  23. Mersten-Katz C, Barnea A, Yom-Tov Y, Ar A (2012) The woodpecker’s cavity microenvironment: advantageous or restricting? Avian Biol Res 5:227–237CrossRefGoogle Scholar
  24. Mock DW, Schwagmeyer PL, Dugas MB (2009) Parental provisioning and nestling mortality in House Sparrows. Anim Behav 78:677–684CrossRefGoogle Scholar
  25. Mock DW, Dugas MB, Strickler SA (2011) Honest begging: expanding from signal of need. Behav Ecol 22:909–917CrossRefGoogle Scholar
  26. Podlas KA, Richner H (2013) The adaptive function of hatching asynchrony: an experimental study in Great Tits. Anim Behav 86:567–576CrossRefGoogle Scholar
  27. Power HW (1980) The foraging behavior of Mountain Bluebirds with emphasis on sexual foraging differences. Ornithol Monogr 28:1–72Google Scholar
  28. Pyle P (1997) Identification guide to North American birds. Part 1. Slate Creek Press, BolinasGoogle Scholar
  29. R Core Team (2017) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna. https://www.R-project.org/. Accessed 12 July 2017
  30. Rising JD, Somers KM (1989) The measurement of overall body size in birds. Auk 106:666–674CrossRefGoogle Scholar
  31. Ryser S, Guillod N, Bottini C, Arlettaz R, Jacot A (2016) Sex-specific food provisioning patterns by parents in the asynchronously hatching European Hoopoe. Anim Behav 117:15–20CrossRefGoogle Scholar
  32. Slagsvold T, Rohwer S (2000) Behavioral domination of food delivery by Tree Swallow nestlings. Wilson Bull 112:278–281CrossRefGoogle Scholar
  33. Slagsvold T, Wiebe KL (2007) Hatching asynchrony and early nestling mortality: the feeding constraint hypothesis. Anim Behav 73:691–700CrossRefGoogle Scholar
  34. Smiseth PT, Bu RJ, Eikenaes AK, Amundsen T (2003) Food limitation in asynchronous Bluethroat broods: effects on food distribution, nestling begging, and parental provisioning rules. Behav Ecol 14:793–801CrossRefGoogle Scholar
  35. Smith MG, Dickinson JL, Rush A, Wade AL, Yang DS (2017) Western Bluebird parents preferentially feed hungrier nestlings in a design that balances location in the nest. Behav Ecol Sociobiol 71:58–64CrossRefGoogle Scholar
  36. Soley N, Siefferman L, Navara KJ, Hill GE (2011) Influence of hatch order on begging and plumage coloration of nestling Eastern Bluebirds. Wilson J Ornithol 123:772–778CrossRefGoogle Scholar
  37. Stalwick JA (2018) Provisioning patterns, diet, and reproduction of Mountain Bluebirds (Sialia currucoides) in clearcut versus grassland habitats. Dissertation, University of SaskatchewanGoogle Scholar
  38. Steen R, Sonerud GA, Slagsvold T (2012) Parents adjust feeding effort in relation to nestling age in the Eurasian Kestrel (Falco tinnunculus). J Ornithol 153:1087–1099CrossRefGoogle Scholar
  39. Stenning MJ (1996) Hatching asynchrony, brood reduction and other rapidly reproducing hypotheses. Trends Ecol Evol 11:243–246CrossRefGoogle Scholar
  40. Stoleson SH, Beissinger SR (1997) Hatching asynchrony, brood reduction, and food limitation in a neotropical parrot. Ecol Monogr 67:131–154CrossRefGoogle Scholar
  41. Whittingham LA, Dunn PO, Clotfelter ED (2003) Parental allocation of food to nestling Tree Swallows: the influence of nestling behaviour, sex and paternity. Anim Behav 65:1203–1210CrossRefGoogle Scholar
  42. Wiebe KL, Slagsvold T (2009) Parental sex differences in food allocation to junior brood members as mediated by prey size. Ethology 115:49–58CrossRefGoogle Scholar
  43. Wiebe KL, Slagsvold T (2012a) Brood parasites may use gape size constraints to exploit provisioning rules of smaller hosts: an experimental test of mechanisms of food allocation. Behav Ecol 23:391–396CrossRefGoogle Scholar
  44. Wiebe KL, Slagsvold T (2012b) Parents take both size and conspicuousness into account when feeding nestlings in dark cavity nests. Anim Behav 84:1307–1312CrossRefGoogle Scholar
  45. Wiebe KL, Vitousek MN (2015) Melanin plumage ornaments in both sexes of Northern Flicker are associated with body condition and predict reproductive output independent of age. Auk 132:507–517CrossRefGoogle Scholar
  46. Winkler DW, Luo MK, Rakhimberdiev E (2013) Temperature effects on food supply and chick mortality in Tree Swallows (Tachycineta bicolor). Oecologia 173:129–138CrossRefGoogle Scholar
  47. Wright J, Both C, Cotton PA, Bryant D (1998) Quality vs. quantity: energetic and nutritional trade-offs in parental provisioning strategies. J Anim Ecol 67:620–634CrossRefGoogle Scholar

Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2018

Authors and Affiliations

  1. 1.Department of BiologyUniversity of SaskatchewanSaskatoonCanada

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