Variation in egg size of Black-tailed Godwits
Verhoeven, M.A.; Loonstra, A.H.J.; McBride, A.D.; Tinbergen, J.M.; Kentie, R.; Hooijmeijer, C.E.W.; Both, C.; Senner, N.R.; Piersma, T. (2020). Variation in egg size of Black-tailed Godwits. Ardea 107(3): 291-302. https://dx.doi.org/10.5253/arde.v107i3.a7 In: Ardea. Nederlandse Ornithologische Unie: Arnhem & Leiden. ISSN 0373-2266; e-ISSN 2213-1175, more |   |
| Author keywords | age; environmental conditions; body condition; state; parental effort |
| Authors | | Top | - Verhoeven, M.A.
- Loonstra, A.H.J.
- McBride, A.D.
| - Tinbergen, J.M.
- Kentie, R., more
- Hooijmeijer, C.E.W.
| - Both, C.
- Senner, N.R.
- Piersma, T., more
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| Abstract | As is the case for most avian species, there is considerable variation in the eggsize of Continental Black-tailed Godwits Limosa l. limosa breeding in TheNetherlands. It is interesting that egg size has costs and benefits yet variesconsiderably at the population level. To better understand this variation in eggsize, we tested its relationship to a suite of individual and environmental factors.We found that egg size can decrease up to 2.8% throughout a breeding seasonand that egg size increases with clutch size by 1.4% with each additional egg inthe clutch. Female body mass and body size explained 5% of the total variationin egg size observed across the population. Furthermore, females winteringsouth of the Sahara laid 3% smaller eggs than those wintering north of theSahara. We also found that egg size increases with age, which may indicateage-related differences in the endogenous and/or exogenous conditions offemales. The variation in egg size was, however, mostly the result of consistentdifferences among individuals across years (repeatability = 0.60). A comparisonof daughters with mothers suggested that most of this individual repeatabilityreflects heritable variation (heritability = 0.64). The actual individual traits thatunderlie this heritable variation among individuals remain mostly undetermined.Smaller eggs did have a slightly lower chance of hatching, but we found no relationshipbetween egg size and chick survival. Finally, nest and chick survivalwere strongly correlated with lay date. Thus, in Black-tailed Godwits, lay datemay actually reflect a female’s endogenous and/or exogenous condition at themoment of egg-laying. This finding may be general across birds, since foodsupplementation experiments usually result in advanced laying and larger clutchsizes rather than in larger eggs. |
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