No one likes being laughed at. And no one likes sibling sabotage. The laughing kookaburra (Dacelo novaeguineae) does both with little regard for what we find objectionable.
Laughing kookaburras are the largest kingfisher species in the world and can be described as stout, stocky, and overall pretty thicc [1]. These creepy kooks, like many frightening critters, are native to Australia [2].
Laughing kookaburras have long caught the attention of humans with their wicked and distinct laughing call. This unnerving sound, most prominently produced at dawn and dusk, was the impetuous for a whole host of nicknames given to them by European settlers: “alarm bird”, “breakfast bird”, “settler’s clock”, “bushman’s clock”, “laughing jackass”, and “ha ha pigeon”. When introduced to the western coast of Australia in the late 1800s, their reputation for killing chickens, ducklings, and the chicks of wild birds led to more negative characterizations such as “the laughing demon” and “a bird of evil” [1,2].
Most academic research on laughing kookaburras falls under three main topics: the kookaburra’s signature laughing call, its cooperative breeding strategy, and its tendency to kill siblings in the nest. Let’s go through each of these to get a complete picture of this menacing little bird.
The Laugh
The kookaburra’s most striking behavior is its eponymous cackling call, which has fascinated humans for centuries. In fact, the indigenous Australian Bidjigal clan have a story about the serious and stern kookaburra. As the story goes, no bird felt the ire of kookaburra as much as cuckoo bird, who laid her eggs in the nests of other birds so she could shirk her parental responsibilities. One day cuckoo bird was caught in the act of laying her eggs in the nest of eagle. Kookaburra watched eagle murder and eat cuckoo for this attempted trickery, and she burst out in laughter for the first time in her life. To this day the kookaburra continues to jovially laugh at the misfortunes and tragedy of others [1].
In reality, the laughing call of the kookaburra serves a much less petty purpose. Kookaburras typically live in groups of 2–9 members and use their call to advertise and defend their communal territory [3]. Morning calls are usually performed just by the dominant mating pair in each group, whereas the entire group joins in for nighttime calls [4].
Cooperative Breeding
Cooperative breeding refers to a social system in which offspring receive care from their parents as well as additional group members [5]. At the core of each kookaburra group is a dominant mating pair. They are aided by female and male helpers—previous offspring of the mating pair that have yet to disperse and begin their own family—that assist in all aspects of raising their younger siblings from egg to nestling.
Surprisingly, a study on kookaburra breeding groups showed that larger groups do not successfully raise more offspring than small groups (once territory quality and mating pair quality are controlled for). In fact, having many female helpers actually reduces breeding success (i.e., the number of offspring that make it to the fledgling stage). This study also showed that male helpers are generally better than female helpers in terms of the rate at which they perform parental care tasks, such as finding food for the nestlings [5]. However, large groups with many male helpers did not do any better than small groups at successfully raising chicks. Additional benefits to living in large groups may include obtaining and defending larger territories and splitting up the energy-intensive duties of raising offspring. There are currently no clear answers to the question of why kookaburras evolved this particular child rearing strategy.
Siblicide
Although kookaburras have a historical reputation for being “snake killers” as well assassins of other bird species [1,2], their most interesting murderous propensity from an evolutionary standpoint is siblicide (i.e., the act of killing one’s sibling). Kookaburras normally breed once per season and lay an average of three eggs [6]. In up to half of kookaburra nests, the chick that hatches third in the nest dies, either directly at the hands (or, in this case, the beak) of its siblings or by starvation due to competition for food [7,8]. Moreover, in a third of nests where the third chick dies, the second-born chick will also die from being outcompeted for food by the dominant chick [6]. Perhaps the most sinister aspect of this whole ordeal is that each chick is born with a specialized hook in the upper portion of its beak used for aggressing and killing its siblings [8]. Immediately after their sibling hatches, dominant chicks will use this hook to attack the base of a sibling’s neck and violently shake them [6]. This is a very rare example of morphological specialization for sibling rivalry; nestlings lose their hook as they grow and get ready to leave the nest [8].
Whether or not the third-born chick survives or gets the ol’ hook to the neck may be influenced by a variety of factors, such as the number of male helpers in the group, the sex of each of the chicks, and the time interval between their hatching. Curious readers can check out the sources below for more information.
The other side to this fierce sibling rivalry is the role of the parents. Neither the parents nor the helpers directly intervene during aggressive sibling interactions. However, it is thought that caretakers modify how much time they spend brooding (laying on the chicks for warmth), which would disrupt the ability for nestlings to interact aggressively with each other [6]. It is also known that parents have some control over the timing of egg laying (which affects the hatching interval between chicks), whether they lay a female or male and in what order, and how intensively they collect food for their young. Thus, the parents have considerable ability to influence factors that promote or deter siblicide, and parents could opt to favor the likely demise of their second- and third-born children if environmental conditions make that the optimal solution.
Given what we now know about the behavioral ecology of this remarkable bird, I propose yet another new nickname for it—something that captures the playfully creepy vibe of its laughing call and premeditated sibling murder: “the spookaburra”.
Adrian Perez is a graduate student in the Animal Behavior Graduate Group at UC Davis. He studies social behavior and disease networks in honey bees.
References:
- Legge, S., 2004. Kookaburra: king of the bush. CSIRO PUBLISHING.
- Collins, D., 2011. The “voice” of nature? Kookaburras, culture and Australian sound. Journal of Australian Studies, 35(3), pp.281-295.
- Baker, M.C., 2004. The chorus song of cooperatively breeding laughing kookaburras (Coraciiformes, Halcyonidae: Dacelo novaeguineae): characterization and comparison among groups. Ethology, 110(1), pp.21-35.
- Reyer, H.U. and Schimdl, D., 1988. Helpers have little to laugh about: group structure and vocalization in the laughing kookaburra Dacelo novaeguineae. Emu, 88(3), pp.150-160.
- Legge, S., 2000. The effect of helpers on reproductive success in the laughing kookaburra. Journal of Animal Ecology, 69(4), pp.714-724.
- Nathan, A., Legge, S. and Cockburn, A., 2001. Nestling aggression in broods of a siblicidal kingfisher, the laughing kookaburra. Behavioral Ecology, 12(6), pp.716-725.
- Legge, S., 2000. Siblicide in the cooperatively breeding laughing kookaburra (Dacelo novaeguineae). Behavioral Ecology and Sociobiology, 48(4), pp.293-302.
- Legge, S., 2002. Siblicide, starvation and nestling growth in the laughing kookaburra. Journal of avian biology, 33(2), pp.159-166.
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