Do parents defend their offspring whenever necessary, and do self-sacrificing parents really exist? To answer this question, researchers of the University of Veterinary Medicine, Vienna examined defence behaviours of parent blue tits. They investigated whether birds would risk everything to protect their young from predators. Their conclusion: parents weigh the risks. It is not only the risk to the nestlings, but also their own risk that plays a role when defending their nests. The results were published in the journal Proceedings of the Royal Society B.
The degree to which parents sacrifice themselves for their children depends on a variety of factors. On the one hand nest predators pose a threat to the young and the parent birds. But also the time of hatching plays a role. Earlier studies have shown that birds born late in the season are more likely to be protected by their parents, as the adult birds often do not have the chance to produce replacement clutches. Older offspring also tend to be protected more readily than younger ones, as much more parental care and energy have already been invested.
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