Sydney cockatoos pass their bin-opening skills to neighbouring flocks

Aplin's account of how a skill takes hold has three parts, and only one of them sits inside the bird. "Intelligence on its own is not enough for a new skill to spread within a species," Aplin said ^[7]. A species also needs behavioural flexibility, and a social network that carries what one individual learns to the next and keeps it in circulation ^[8]. "It needs a culture," she said ^[9]. Parrots keep learning new sounds throughout their lives, a capacity the article attributes otherwise only to whales, dolphins, crows and humans ^[22].

The plexiglass box goes after the first two parts under conditions the team controls. It is octagonal, about half a metre across, and each compartment has to be opened a different way, with an almond inside ^[11]. Watermelon, a male carrying wing mark 11, had never solved a task like it ^[12][14]. He pulled the drawer open with his beak and took the almond ^[14]. He worked the lever quickly ^[15]. The compartment whose base had to be twisted took him several tries, and then he flew off ^[16]. He handled three mechanisms in one visit, and one of them took repeated attempts ^[24].

The box measures individual innovation on an unfamiliar object, and the trial described in Aplin's video covers one bird ^[17][25]. The transmission claim rests elsewhere, on the bins: the birds pass lid-opening to their own flock and to neighbouring cockatoo communities, and they often defeat the weights and jammed hinges residents add ^[5][4]. The article does not include figures for how fast a secured lid falls or what share of a street's bins get opened ^[26]. A resident would most want the comparison those figures would allow: whether the skill travels faster than the countermeasures ^[26].

The paint makes the longer question tractable. Each bird gets three dabs applied with a small sponge, and the team does not have to catch it ^[20]. From those marks they record who grooms with whom, who roosts and forages together, and which individuals cross into neighbouring groups ^[20]. Aplin has known many of the birds for years ^[23]. The birds have learned the researchers too, who wear the same blue coveralls and signal with a whistle ^[19]. "The cockatoos now flock toward us as soon as we show up," Aplin said ^[18].

A weighted lid is being tested by an animal up to 50 centimetres tall that already opens drinking fountains by twisting the handle with its feet, in Brisbane as well as Sydney ^[21][1]. When one bird beats the weight, the solution spreads to its own flock first and then to the community next door ^[5].