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Journal für Ornithologie

, Volume 127, Issue 3, pp 291–301 | Cite as

Clutch size, intraclutch egg size variation, and breeding strategy in the GoldcrestRegulus regulus

  • Svein Haftorn
Article

Summary

In Fennoscandia the Goldcrest regularly lays two clutches per breeding season. Near Trondheim in Central Norway (about 63° N) the mean size of 11 first clutches was 10.4 (9–12) eggs and of 10 second/repeat clutches 9.4 (8–11) eggs. Mean egg length was 13.49 mm, breadth 10.35 mm, mean weight of freshly-laid eggs 0.78 g, volume 737 mm3 and shape index 130.6. The correlation coefficient for egg length against weight was 0.47, and for egg breadth against weight 0.77. For the four clutches studied in more detail, all egg dimensions, except the shape index, increased with the laying sequence. On average, the last-laid egg was 20.1 % heavier than the first-laid egg, or 5.6 % heavier than the mean weight for the whole clutch. The 3–5 last-laid eggs in the clutch deviated by about the same magnitude from the clutch mean. Because of the pronounced asynchrony in hatching, the size-hierarchy within a Goldcrest brood may be considerable, at least 1:5. The survival chances of the smallest young in a brood apparently depend mainly on the prevailing food supply. The primary advantage of hatching from a relatively large-sized egg is probably that such a hatchling is strong enough to secure itself a favourable feeding position in the crowded nest, in which the young often form 2–3 horizontal layers. The parental selection of food is adjusted to the size of the young, even in a brood with a marked size-hierarchy. It is concluded that the Goldcrest has evolved a brood reduction strategy.

Keywords

Clutch Size Shape Index Feeding Position Brood Reduction Favourable Feeding 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Gelegegröße, Variation der Eigröße und Brutstrategie beim Wintergoldhähnchen (Regulus regulus)

Zusammenfassung

In Fennoskandien zeitigt das Wintergoldhähnchen regelmäßig zwei Gelege pro Brutsaison. In einem Kontrollgebiet bei Trondheim in Mittelnorwegen (ca. 63° N) betrug die mittlere Gelegegröße für 11 Erstgelege 10,4 (9–12) und für 10 Zweit- bzw. Ersatzgelege 9,4 (8–11) Eier. Die mittlere Eilänge betrug 13,5 mm, die Eibreite 10,35 mm, das mittlere Frischvollgewicht 0,78 g; das Volumen maß 737 mm3, der Eiformindex (=Länge/Breite × 100) 130,6. Die Korrelation zwischen Länge und Gewicht betrug 0,47, zwischen Breite und Gewicht 0,77. Bei vier genauer untersuchten Gelegen nahmen alle Eidimensionen mit Ausnahme des Eiformindex mit der Legefolge zu. Im Mittel war das letzte Ei 20,1 % schwerer als das erste oder 5,6 % schwerer als das mittlere Gewicht des gesamten Geleges; letzteres gilt auch für die 3 bis 5 zuletzt gelegten Eier. Als Folge des bemerkenswert asynchronen Schlupfes sind die Größenunterschiede innerhalb einer Goldhähnchenbrut beachtlich, nämlich mindestens 1:5. Die Überlebenschancen des kleinsten Jungen einer Brut hängen offensichtlich vor allem vom Nahrungsangebot ab. Der primäre Vorteil eines Jungen aus einem großen Ei liegt möglicherweise darin, daß dieser Nestling stark genug ist, um sich eine günstige Position im dichtbesetzten Nest bei den Fütterungen zu sichern. Die Jungen liegen oft in zwei bis drei Schichten übereinander. Die Nahrungswahl der Altvögel richtet sich nach der Jungengröße, sogar in einer Brut mit deutlichen Größenunterschieden. Das Wintergoldhähnchen hat wahrscheinlich die Strategie einer Brutreduzierung in Anpassung an knappes Nahrungsangebot entwickelt.

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Copyright information

© Verlag der Deutschen Ornithologen-Gesellschaft 1986

Authors and Affiliations

  • Svein Haftorn
    • 1
  1. 1.University of Trondheim, The MuseumTrondheimNorway

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