Powerful Ravens Sabotage Others’ Relationships

If we’re lucky, this is behavior we haven’t seen since high school. The coolest individuals can’t stand to see others gaining social status, so they cut down any peers who are starting to elevate themselves. Ravens have to live with this behavior all the time. When the top-dog birds see others building new relationships, they attack these birds or put themselves in the middle. They may as well be spreading rumors or defacing each other’s lockers.

Wild ravens living in Austria were the ones to reveal this behavior to scientists. The ravens, a group of about 300 birds in the Austrian Alps, have discovered that a local zoo is a convenient source of food. So the wild birds hang around the captive animals year-round (they especially like the wild boar enclosure) and steal their provisions. Because of this, they’re used to seeing humans nearby.

Lees meer: Discover

Bad news for kids: Parents do not defend their offspring at all cost, bird study shows

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.

Lees meer: ScienceDaily

Parental defense of offspring and life history of a long-lived raptor

Auteurs: Anders Pape Møller, Jan Tøttrup Nielsen
Bron: Behavioral Ecology (2014) 25 (6): 1505-1512. doi: 10.1093/beheco/aru130
Abstract: Animals with parental care defend their offspring with an intensity reflecting parental investment. Parental investment theory predicts that parents should take risks relative to their residual reproductive value. Therefore, parental defense should change consistently with age reaching a peak at middle age, and it should vary consistently with age at start and end of reproduction.

We recorded the intensity of parental defense of offspring in 410 female goshawks Accipiter gentilis throughout their lives, ranging from timid females that barely approached a human intruder at the nest to aggressive females that physically attacked the human. Females were consistent in their level of defense throughout life, and aggressive females were mated to aggressive males. Investment in reproduction as reflected by laying date, clutch size, and brood size showed a bell-shaped relationship with age.

Females that started to breed at a young age were less aggressive than females that started late. Likewise, females that finished reproduction at a young age behaved less aggressively than females that finished at an old age. The intensity of defense of offspring peaked at an intermediate age followed by a decrease into old age and senescence. Females that started to breed early during the season were more aggressive than late breeders. These findings are consistent with the hypothesis that the intensity of parental defense of their offspring reflects parental investment and patterns of aging.