Parental investment in eggs and its effect on nestling growth and survival in Magellanic Penguins

Abstract

Life-history variables evolve in response to cost-benefit trade-offs. For birds, larger eggs are thought to be beneficial for development of offspring but are energetically costly to produce. Further, egg-size dimorphism within or between clutches can vary with proximate and ultimate causes. We undertook a correlational study to evaluate parental investment in eggs by Magellanic Penguins (Spheniscus magellanicus) and how it affects the growth and survival of nestlings in Puerto Deseado, Argentina, over 3 years. We evaluated the variables that affected egg-volume and yolk-area (using a nondestructive technique), and determined the effects of egg-volume and yolk-area on growth and survival of young. Females in good body-condition laid larger second eggs and, in good years (i.e. years of high reproductive success in the colonies of the study area), yolk-area of second eggs was larger than that of first eggs. We found a positive association between eggvolume and nestling body-size and yolk-area was positively related to nestling survival. Our results suggest that the size of eggs within clutches varied with year and female body-condition. Moreover we demonstrate for the first time that yolkarea is a strong predictor of nestling survival in Magellanic Penguins.

Egg temperature and initial brood patch area determine hatching asynchrony in Magellanic penguin Spheniscus magellanicus

“…Probably, this high dimorphism is responsible for the difference in incubation position between eggs found in Eudyptes. Magellanic penguins, on the other hand, have only a 2% egg volume dimorphism (Boersma andRebstock 2010, Barrionuevo andFrere 2014), and this could be the reason why we did not find differences in the incubation position and, therefore, no effect on hatching asynchrony.…”

“…To maintain the humidity of the incubator, we filled a container at a constant level with tap water and we also rotated the eggs once a day, manually. To measure the yolk swelling, we took a picture of the eggs in an Ovoscope, especially designed to trans‐illuminate penguin eggs (for more information see Barrionuevo and Frere ), on the laying day of each egg, and 4 d later after being exposed to the different temperatures. Then, with the computer program Image Pro‐Plus 4.5 we measured total egg area and yolk area for day 0 and day 4.…”

Morphometric Variation During Chick Development in Interior Double-Crested Cormorants (Phalacrocorax auritus)

“…The reason for this anomaly is unknown but likely reflects maternal condition during egg formation. Adult body condition upon arrival at the breeding grounds could result in larger chicks (Hebert et al 2008;Barrionuevo and Frere 2014). The nutrient quality of the yolk sac is likely improved in cormorants wintering near and foraging at aquaculture facilities (Navara and Mendonça 2008).…”

An experimental approach to the brood reduction hypothesis in Magellanic penguins

“…The colonies are very synchronous, all eggs are laid within two weeks. Intra‐clutch egg size dimorphism is of 2%, with the second egg larger than the first (Barrionuevo and Frere ). Egg volume affects only nestling mass during early stages of growth (Barrionuevo and Frere ).…”

“…Intra‐clutch egg size dimorphism is of 2%, with the second egg larger than the first (Barrionuevo and Frere ). Egg volume affects only nestling mass during early stages of growth (Barrionuevo and Frere ). Both parents alternate incubation tasks, each taking an initial incubation bout of 15 d and then shorter shifts until hatching, where females usually take the first incubation bout (Boersma et al ).…”