Cuckoos: Outsourcing Childcare, Hogging the Bed

(Via:)
(Via: Batsby)

Common Name: Parasitic Cuckoos

A.K.A.: Subfamily Cuculinae (Family Cuculidae)

Vital Stats:

  • Range in length from 15-63cm (6-25”) and weigh between 17g (0.6oz.) and 630g (1.4lbs.)
  • The majority of cuckoos are not parasites, but around 60sp. are (about 56 in the Old World, and 3 in the New World)
  • Babies of brood parasites are initially coloured so as to resemble the young of the host species

Found: The cuckoo family is present throughout the temperate and tropical world, with the exceptions of southwest South America and regions of North Africa and the Middle East. Parasitic cuckoos occupy a subset of this range, principally in the Old World.

Cuckoo Map

It Does What?!

Parenting is tough… less sleep, less free time, all those all those hungry mouths to feed. What’s a busy mother to do? You know you need to perpetuate the species, but who has the time? Impressively, cuckoos have come up with the same answer that many humans have: outsourcing! Involuntary outsourcing, in this case.

One of these things is not like the others.(Via: Timothy H. Parker)
One of these things is not like the others.
(Via: Timothy H. Parker)

Once a female cuckoo has mated and is ready to lay the eggs, rather than build a nest and slog her way through childcare, she waits for another female with freshly laid eggs to take off for some food and just lays her egg there, spreading her clutch across several nests. In theory, when the duped female returns, she’ll just settle in and care for the new egg along with her own. Cuckoo eggs have a shorter incubation period than that of their host, so the foreign egg usually hatches first, at which point the baby cuckoo just gives the other eggs (or chicks, if the timing didn’t quite work out) a good shove, and enjoys having both a nest and a doting mother to itself. The cuckoo chick will tend to grow faster than its host species, so it keeps its adoptive parent busy with constant begging for food, having eliminated the competition.

But this wouldn’t be a fun evolutionary arms race if the host species just took it on the chin. Birds plagued by cuckoo eggs have worked out several ways to try to cope with the problem. First off, and not surprisingly, they’ve developed a burning hatred of cuckoos. Adult cuckoos seen in the area of the hosts’ nests will immediately be mobbed and run off by a group of angry mothers. The cuckoos, however, have learned to use this to their advantage by having the male of a pair tease and lure the angry mob away while the female lays her eggs in peace. Advantage: cuckoos.

And this, kids, is how you deal with those annoying younger siblings.(Via: M. Bán, PLoS ONE)
And this, kids, is how you deal with those annoying younger siblings.
(By: M. Bán, PLoS ONE)

A second strategy used by the parasitised birds is to learn to recognise foreign eggs and pre-emptively toss them out of the nest. Cuckoos responded to this in two ways. First, they slowly evolved eggs to match those of their host bird in colour and size (or, in the case of covered nests, very dark eggs which aren’t easily seen at all). Bird species with higher levels of egg rejection just end up with cuckoo eggs which look more and more similar to their own. Second, if a host does reject the foreign egg, the cuckoo who laid it will sometimes come and just destroy the entire nest, killing anything left inside it in an act of motherly vengeance. Advantage: cuckoos.

A third strategy, developed by the Superb Fairy Wren (not to be confused with the equally floridly named Splendid Fairy Wren) is a bit more clever. As soon as the host mother lays her eggs, she begins to sing to them in a very specific pattern. Now, in this case, the cuckoo egg will hatch around the same time as her own eggs, but was deposited there several days later than her own. This means that her own chicks have been sitting there, unborn, learning her song for a longer period of time than the cuckoo has. Once the eggs are hatched, only her own chicks will be able to properly replicate her calls. Can’t sing the song? No food for you. And if, prior to starving to death, the parasite chick does manage to push her chicks out of the nest, the mother will fail to hear the proper response at all and know to simply abandon the nest entirely. Advantage: Fairy Wren. Superb indeed.

Shrikes: don't try to outsmart a bird that kills mammals for sport.(Via: Arkive.org)
Shrikes… don’t try to outsmart a bird that kills mammals for sport.
(Via: Arkive.org)

There is at least one known case of a former host species throwing off the yoke of cuckoo parasitism entirely. The red-backed shrike, aside from being particularly murderously aggressive toward adult cuckoos (and many other things), became very good at identifying cuckoo eggs, very quickly. So quickly, in fact, that researchers believe the cuckoos simply didn’t have time to adapt. In laboratory experiments, the shrikes correctly identified and rejected 93.3% of all cuckoo eggs placed in their nests. Pretty good pattern recognition for a brain the size of a pea. While cuckoo-red shrike parasitism has been known historically for some time, it hasn’t been seen in nature for the last 30-40 years.

Shrikes for the win.

Fun Facts:

  • Even typically non-parasitic cuckoos will sometimes lay their eggs in the nests of their own or other species, but will still help to feed the chicks (parental guilt, perhaps?).
  • The eggshells of parasitic cuckoos are unusually thick, helping prevent them from cracking as their mother drops them from above into the host nest.
  • Striped cuckoos, not content to just shove their adoptive siblings out of the nest, actually peck them to death with their beaks.
  • A few birds deal with homicidal cuckoo chicks by building steep-sided nests, making it difficult for any chick to be pushed out (and raising them as one big, happy family, I guess).

Says Who?

  • Colombelli-Négrel et al. (2012) Current Biology 22: 2155-2160
  • Feeney et al. (2012) Animal Behaviour 84: 3-12
  • Lovaszi & Moskat (2004) Behaviour 141(2): 245-262
  • Spottiswoode & Stevens (2012) American Naturalist 179(5): 633-648
  • Wang & Kimball (2012) Journal of Ornithology 153: 825-831
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Necessity is the Mother of Invention, or, How to Eat Like a Shrike

(By: Arthur Morris, Via: Livebooks Blog)

Common Name: The Shrike

A.K.A.: Family Laniidae

Vital Stats:

  • Family consists of three genera and around 30 species
  • Shrikes range in size from 17cm (6.5”) up to 50cm (20”) long
  • Feathers may be black and white, cream, grey, or brown

Found: Various species found in North America, Southern Africa, and Eurasia

It Does What?!

Sometimes a creature aspires to a spot a little higher on the food chain, but doesn’t quite have all the equipment to get there. Behold the shrike, the bird that wishes it were a raptor. Like birds of prey, shrikes have strong, hooked beaks, sharp eyes, and an appetite for meat, but they’re missing a couple of important features. First, and most important… no talons. Shrikes can’t grab a victim and tear it into pieces like a hawk or falcon could. And second, no crop (a sort of internal storage pouch), so they can’t eat a large quantity of meat in a single sitting.

Not to be deterred by their anatomical shortcomings, these inventive go-getters have come up with a single solution to both problems. Two birds with one stone, if you will. After dispatching their prey with a quick beak to the back of the neck, shrikes will carry the carcass to a nearby shrub and actually impale it on a short branch or thorn. Aside from looking incredibly badass, this serves to anchor the body in one place, allowing the shrike to use its beak to rip the meat into pieces. What’s more, the bird can just leave its leftovers hanging there for later, like the meat locker at a butcher shop. [Wondering what that looks like? Here’s a video, set to appropriately ominous music.]

And now they’re learning to use human technology…
(Via: Nature Saskatchewan)

What kind of prey are we talking about here? Anything from small insects right up to mice, frogs, lizards, and other birds. There’s even a record of one killing and impaling a good-sized bat. Impressively, shrikes have also hit on the value of ageing their food – one species hunts the toxic lubber grasshopper of the southern United States. The dead grasshoppers are then left hanging for several days to let the poison degrade before being eaten. Clever birds.

Shrikes are monogamous and share in parenting duties; when the female is sitting on eggs, it’s the male’s job to go out and kill something nutritious for two. Of course, this makes selecting a good hunter an important task for females during mate selection. When a single male wants to advertise his skills, he makes a conspicuous display of his biggest, most impressive kills for any prospective ladies. Once he’s gotten one’s attention, he performs a mating dance that mimics the action of impaling prey on branches and then feeds her from his assortment of carcasses. (Be sure to include this point next time you’re explaining ‘the birds and the bees’ to someone.)

The owner of this lizard is probably off getting lucky.
(Via: Wikimedia Commons)

I guess when you have only one major skill, you want to make the most of it, because aside from eating and attracting mates, shrikes also use their impaling trick for communication. Bonded pairs are territorial and will defend their terrain from others of their species. In a sort of macabre message to would-be trespassers, the couple will mount their kills around the borders of their land, perhaps in an effort to show others what could become of them if push came to shove. (Did I mention these things actually have a comic book monster named for them? Eat your heart out, Batman.) Unfortunately for them, researchers note that this action often resulted in the prey being snatched by opportunistic passers-by and having to be replaced. It’s so hard to look murderous when everybody keeps stealing your victims…

[Fun Fact: Shrikes with young chicks will often eat only the head of their prey, saving the bodies for the kids. ‘Cause that’s just good parenting.]

Says Who?

  • Keynan & Yosef (2010) Behavioural Processes 85: 47-51
  • Sarkozi & Brooks (2003) Southwestern Naturalist 48(2): 301-303
  • Smith (1973) Behaviour 44(1/2): 113-141
  • Yosef & Pinshow (2005) Behavioural Processes 69: 363-367
You’re next.
(Via: Tough Little Birds)

The Cost of Eighty Million Years in Paradise

(Via: The Life of Animals)

Common Name: The Kakapo, The Owl Parrot

A.K.A.: Strigops habroptila

Vital Stats:

  • Males can grow up to 60cm (24”) long and weigh up to 4kg (8.8lbs.)
  • Average life expectancy of a healthy kakapo is 95 years
  • Breeding begins around age 9; females lay 1-3 eggs per clutch
  • Main mammalian predators are rats, cats, ferrets, and weasels

Found: Traditionally, across large areas of both major islands of New Zealand; today, mostly on small, protected island reserves nearby

It Does What?!

Strange things happen when you leave a few species alone on a distant island for a few million years. Places like New Zealand, Australia, Madagascar, and Hawaii are (or were) full of plants and animals that seem alien compared to rest-of-the-world standards. This is often due to a set of conditions and evolutionary challenges unlike those seen on the continent. Life on New Zealand is particularly interesting, having been heavily shaped by the fact that the only terrestrial mammals there are bats. Every animal that evolved there did so without the pressure of having to avoid toothy predators stalking them through the forest. Ever wonder what birds would be like without anything on the ground trying to kill them?

“I’m just big boned, okay?”
(Via: Gothic Atheist)

If so, meet the kakapo, the world’s largest, fattest parrot. And the only one that can’t fly. Isolated in New Zealand when the islands separated from the continent over eighty million years ago, the native parrots eventually lost their strong flight muscles and stiff, rigid wing feathers, trading them for greater size and the ability to store a half inch thick layer of fat under their skin to sustain them in lean times. This change also slowed their metabolism, resulting in their being one of the longest-lived birds out there, with a maximum recorded age of 120 years. Slothlike, these peaceful, nocturnal creatures spend most of their waking hours climbing (yes, climbing) from tree to tree, eating fruit and foliage. Unlike sloths, however, they can take a quicker route down, simply leaping from the tree and spreading their stumpy wings in what’s probably a very amusing imitation of a parachute. Unsurprisingly, they’ve developed quite strong legs, and can cover distances of several kilometres at a jog.

The most fascinating aspect of the kakapo lifestyle, though, has to be its mating routine. Unlike most parrots, kakapos aren’t monogamous and don’t share parenting duties. Every three to six years, when fruit crops are particularly good, male kakapos will stake out a small territory on high ground, fighting with other males for the best spots. The “best spots” in this case being those with the best acoustic qualities, such as those backed by a rock wall which can reflect sound outward over the land. Having obtained his mating area, he will construct a series of pristine paths leading up to it (for the ladies), as well as a large bowl-shaped depression in the earth, which acts as an amplifier. Kakapo-sound-system completed, he’s ready to get down to business. The male stands in his bowl, inflates a sac in his chest, and emits a series of eerie, low frequency booms, like distant cannons, loud enough to be heard several kilometres away. He continues to do this, all night, every night, for up to four months, losing up to half his body weight in the process. The female kakapo has it somewhat easier. She simply approaches the emitter of her favourite booms, he performs a short dance routine for her, she gets what she came for, then walks on home to lay her eggs.

“I could hide better if you two would quit staring.”
(Via: Pour L’animal)

Before the colonisation of New Zealand, the islands were reportedly teeming with these birds, so successfully specialised were they for their unusual environment. Their only natural predators were birds of prey, from which they hid by freezing and blending into the surrounding greenery. Sadly, specialisation is often a one-way street that you can’t back out of if your environment suddenly changes. The features that made the defenseless kakapos good at avoiding avian predators (like their tendency to freeze), made them terrible at avoiding the carnivorous mammals, such as cats, that came with colonisation. Despite having powerful legs with large claws, the birds seem unaware that they can be used as weapons. Worse, their natural curiosity and lack of fear in approaching humans often landed them on both Maori and European dinner tables.

Enormous efforts have been made over the last century to prevent these big, gentle birds from going extinct. As of this year, there are still only 126 known to exist (each with its own name and radio transmitter), but they are a slowly expanding population, thanks to their relocation to three protected, largely predator-free islands. Expectant mothers even have their own nest watchers, who sneak in to cover the nests with electric blankets while mom pops out for a bite. Free babysitting- seems like the least we can do.

“How do YOU like it?!”
(Via: BBC’s Last Chance to See)

[Fun Fact: Conservationists have had to scale back on the supplemental food they had been giving the kakapos during mating season. It turns out a well-fed kakapo will produce mostly male chicks. Not what you need when you’re trying to rebuild a population.]

[Also: Kakapos use their fine facial feathers like whiskers, walking with their faces near the ground to sense the terrain.]

Says Who?

  • Douglas Adams & Mark Carwardine (1990) Last Chance to See. Pan Books, London [This is a fantastic book. Highly recommended.]
  • Grzelewski (2002) Smithsonian Magazine, October Issue
  • Sutherland (2002) Nature 419: 265-266