All that time ducks spend sitting on their nests pays off, and not just by protecting their eggs from hungry foxes. The warmer a duck egg stays, the stronger the immune system of the duckling that hatches , according to a new study. Researchers incubated the eggs of wood ducks (Aix sponsa) at 35˚, 35.9˚, and 37˚C, temperatures within the normal range for eggs in the wild. When the eggs hatched, the scientists challenged the immune system of each duckling by injecting it with foreign cells. The birds that had been incubated at the lowest temperature had the least swelling at the injection site and the fewest antibodies in their blood. That indicates that their bodies were not as robustly attacking the foreign cells, the team reports today in Biology Letters. In the wild, ducklings are exposed to pathogens and parasites as soon as they hatch, and small differences in immune function could determine whether the hatchling survives or not.
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