High temperatures change parenting behavior in birds

So here's a statistic I'd never heard before: Between 1979 and 2003 years, more Americans died from heat exposure than from hurricanes, lightning, tornadoes, floods, and earthquakes combined.


That comes from Jason Goldman, a scientist and science blogger, who has a post up today about how animals that thrive in extreme heat situations actually manage to do that. Specifically, he's writing about a recent paper that studied how harsh environments change the parenting behavior of desert birds. Apparently, the hotter the nest, the more the male bird is likely to be involved in incubating the eggs.

Biparental care, which is the care of offspring by both male and female parents, represents a classic example of the trade-off between cooperation and conflict in social behavior in the animal kingdom. If they cooperate, parents can work to improve the odds of the survival of their offspring. By withholding care, however, an individual can potentially survive longer and increase the odds of successful breeding later in life. Assuming that biparental care is even possible in a given species, mathematical models expect it to occur anytime the possibility of offspring survival is significantly greater than when cared for by a single parent. In particular, the harsh environment hypothesis predicts that parents should both contribute to the care of their young in environments susceptible to harsh weather conditions, where food is scarce, where there is intense competition for resources, if desiccation of eggs is a possibility, or in areas where the offspring are regularly preyed upon.

The Kentish plover provided Al-Rashidi with the opportunity to conduct a particularly clever experiment. These birds lay their eggs on the ground, which means that the eggs as well as both parents have direct exposure to the surrounding environment. Some nests are located under bushes, and are therefore naturally protected from direct sunlight, while others are out in the open. This provided an obvious way for Al-Rashidi to create two experimental groups – one in direct sunlight and a second in the shade. In general, males tend to sit on the nest during the cooler nighttime, while females tend to take the daytime shift. The problem is that the females risk overheating if they incubate the eggs all day. The harsh environment hypothesis, therefore, predicts that the warmest nests will not only show evidence of more biparental care but that the two parents will take turns more often throughout the day.

... As expected, males and females both spent more time sitting on the exposed nests than the covered ones over the whole day, and as predicted by the harsh environment hypothesis, there were more change-overs – that is, they took turns more often – during the hottest part of the day at the exposed nests.