By Noah Bressman
Everyone knows that the mama bird gets worms to feed to her hatchling chicks. If the mama bird is like the comedy rapper Flynt Flossy and has “got a lot of chicks”, she may not be able to feed them evenly. Some will then grow faster and have a better chance of survival while others may starve. What happens if the mama gives uneven resources to the chicks before they even hatch? If the mama bird has got a lot of eggs, she may not be able to give them all the same amount of her body heat. How would the chicks fair then, given equal access to resources when they hatch? A team of scientists led by Sydney Hope of Virginia Tech sought to answer this very question using tiny, adorable wood duck (Aix sponsa)ducklings.
Hope and colleagues collected eggs from wood duck nests around the Savannah River in South Carolina (making sure to leave some eggs still in the nests and replacing the ones they took with wooden eggs so the mama would not abandon the nest). They then incubated half of the eggs at 35°C and 36°C, which are natural nest temperatures under mama’s butt. Such a small difference in temperature is realistic in natural nests depending on how the eggs are organized, but could not possibly make a real difference, right? In crocodiles, a one degree difference is the difference between the eggs hatching as girls or boys, so perhaps it could also have an effect on ducks. After the eggs hatched, ducklings from both groups were mixed together and given opportunities to warm up under a heat lamp and get food.
The ducklings from the slightly warmer temperature did hatch a little earlier and had slightly bigger bills and bodies than the cooler ducklings. However, they both behaved the same; they spent the similar amounts of time warming up and eating. This surprised Hope and colleagues, who predicted that the cooler ducklings would spend more time by the heating lamp and eat more frequently to compensate for their differences.
Instead, the warmer ducklings spent the same amount of time eating, but ate a bit more during each meal because their bigger bills fit more food. Because they had more food, they grew quicker and larger, needing more food and allowing them to get more food, growing larger and larger, leading to a positive feedback loop. This means that the ducklings that were born with a small advantage have an advantage for life compared to their siblings. It goes to show, the early (hatching) bird really does get the worm.
Dr. Noah Bressman is a Postdoctoral Fellow at Chapman University, studying fish biology, biomechanics, biomaterials and behavior. You can find more at NoahBressman.wixsite.com/Noah or @NoahwithFish, or contact him at NoahBressman@gmail.com.