1878 | Berlin, Germany

Rosy-faced lovebird (Agapornis roseicollis) feather tucking

Ever packed for a holiday, and just couldn't fit everything in? Imagine if all you had to carry things with was a beak and wings—and forget about the suitcase. Today we meet a blushing bird that overcomes all those limits by shaking a tail feather, and sticking things where they normally don’t belong.

‘The illustrations are admirable’

If you wanted to learn about animals in late 19th century Germany, there was only one book you needed: Alfred Edmund Brehm’s Thierleben, or Life of Animals. It was a roaring success, with Brehm using his travel experience and keen eye for detail to capture the spirit of the natural world. We can think of him perhaps as the David Attenborough of his day.

The first edition of six volumes was published from 1864 to 1869, and the second edition (expanded to ten volumes) was released just a few years later in 1876-79. They weren’t just well known in Germany: in June 1868 Charles Darwin wrote to Brehm’s publisher, noting that:

I have twice strongly recommended Mr Murray [publisher of Darwin’s Origin of Species] to bring out a translation of Brehm’s Thierleben, for I have now read a considerable part of the book & think it quite excellent, & the illustrations are admirable.

The illustrations were so admirable, in fact, that Darwin proposed to use the same engraved blocks that were created for Thierleben to print images in his forthcoming Descent of Man. He asked the publisher to send him 15 of those blocks, reassuring them that ‘I should of course in each case state that they were taken from Brehm’s work’. He did end up using 14 of those illustrations in Descent, even as an English translation of Theirleben’s birds material was published as Cassell’s Book of Birds in the early 1870s.

It’s in Volume II of Thierleben’s 2nd Edition, released in 1878, that we meet the rosy-faced lovebird, Agapornis roseicollis. It’s introduced with a glowing assessment (translated here from the German):

Their nature and demeanour stand out favourably from those of other dwarf parrots: they are evidently more intelligent, physically and spiritually more active than these, have all the courageous qualities of the same and others that are very appealing to them. Perhaps you don't say too much if you count them among the most graceful of all parrots. They always keep their plumage in the best order, so they always look extremely clean, they are also…extremely tender towards their mate and devoted in the care of their young.

Brehm also gives us one of those fine engraved pictures that caught Darwin’s attention. Not only do we see these rosenpapageien birds in a variety of poses, but in the top right corner—I’ve enlarged it on the right here—is a bird about to enter its nesting hole. And sticking out of its lower back are what appears to be spines, or possibly a nasty worm infestation:

Luckily it’s neither of those things. That image reflects Brehm’s personal experience raising these lovebirds in his home, since at the time no western scientist had observed the birds building nests in their native southwest Africa. Initially, Brehm found that his pair of captive birds seemed eager to mate and build a nest, but ‘they obviously lacked something’.

He thought it might be a diet change, so he added a leafy willow branch to their usual seed feed. And this happened:

In a few minutes they had perched upon it, quickly stripping the leaves and gnawing the buds and bark. At first it seemed to me that this work was also only being undertaken out of a lust for destruction, not nourishment; however, as I continued to watch carefully, I noticed that my birds had finally found the building materials they wanted. Skilfully the female spliced ​​off a piece of willow six to ten centimeters long, grasped it with her beak so that one end protruded about three centimeters, turned around, ruffled her rump feathers, fumbled in them with her beak, and re-smoothed her feathers with the splinter fastened between them. A second, third, sixth, and eighth were detached and fastened in the same way; some fell to the ground without being noticed, some were pulled out from between her feathers again by her all too eager mate; in the end, however, some stuck; the parrot rose, flew slowly and carefully towards the nesting box, slipped in with a full load and returned empty.

With the nest-building underway, the pair of lovebirds finally mated, and began raising chicks. Here’s what Brehm was trying to represent in that engraving—this short video shows a lovebird deftly stripping out leaf midribs to add to her collection:

And again in photo form…

Strip mining

Rosy-faced lovebirds use those strips to build a cup-shaped nest inside a natural hollow. It’s only the female of the monogamous pair that regularly carries material this way—although males have been seen on occasion to try—and it’s a remarkably ingrained behaviour for them. In captivity the same birds will tear up paper, cardboard, anything that allows them to form long strips (just google ‘lovebird paper tail’ to see examples from around the world). And it all goes straight into their back pocket.

Some of their close lovebird relatives also carry things between their feathers, but none do so with the skill and to the extent seen in Agapornis roseicollis (or Psittacus roseicollis as it was once known). For example, females of A. cana, A. taranta and A. pullaria have been seen putting small pieces of bark, seed husks, leaves and more under their feathers, then flying to their nest and using them to build up a soft cushion inside. But these other lovebirds stash their little treasures all around their body, not just in the back and tail area.

The fact that multiple species all have that tucking behaviour has led to the idea that it’s a primitive condition, one that existed in a common ancestor. Other lovebirds carry nesting materials in their beak, though, so genetic research was needed to help sort out what evolved when. And it turns out that the birds that use small fragments to line their nests likely do represent the original behaviour for the group. Our A. roseicollis ‘strip-tuckers’ are then intermediate between those originals and another even more recent adaptation in which beak-carrying lovebird species (e.g., A. fischeri, personata, nigrigenis and lilianae) also build more complex domed nests.

Note that sometimes rosy-faced lovebirds will make use of an existing weaver bird nest, building their shelter inside. They don’t build such intricate structures as those of the weavers (we’ll cover those another time), but you may see A. roseicollis hanging around those nests, like these in Namibia:

The differences in nest-material-carrying between the rosy-faced lovebirds and their relatives in the same genus naturally led to one of the standard questions of science: what would happen if we got two different species to mate with each other? Would a hybrid bird inherit the behaviour of one parent or the other, or come up with something altogether new?

A cautionary tail

Cut to the Cornell Ornithology Lab, early 1960s. In what is now literally a textbook example of hybridisation, William Dilger and his student Paul Buckley examined what happened when they crossed A. roseicollis with A. fischeri (or Fischer’s lovebird, from eastern Africa). The latter doesn’t tuck away nesting strips in their tail while building their covered nests, but instead Dilger noted that:

fischeri females carry nesting material (strips of bark, paper, or leaves and more substantial items such as twigs) one piece at a time in the bill.

The rosy-faced approach that we’ve been talking about involves transporting multiple pieces at once, with the beak free for other purposes, while the Fischer’s lovebirds keep a tight grip on their solitary strip. Which route would the hybrid children of these species adopt?

As it happens, it’s a bit of a mess. I’ll let Dilger count the eight steps to failure, in a 1962 report:

Hybrid females almost always attempt, at least, to tuck nesting material in the feathers but are never successful in carrying in this way for several reasons: (1) Proper movements for tucking are made, but the bird seems unable to let go of the strip even after repeated attempts at tucking; (2) The strip is tucked but soon falls out—usually while the bird is busy cutting the next one; (3) Tucking is attempted at locations other than the lower back and rump—a more ‘primitive’ or ancestral pattern; (4) The strip is grasped somewhere other than at one end, making proper tucking impossible; (5) Tucking movements are begun; but the behavior gradually merges into preening movements, and the strip falls unnoticed to the ground; (6) Tucking-intention movements are made but not completed; (7) Inappropriate objects such as twigs are tucked; and (8) Sometimes the bird attempts to get its bill near its rump by running backward.

From seemingly forgetting what they’re doing, to improper tucking, to not letting go, to actively chasing their own tail, these literally mixed-up lovebirds have no chance. Even after years of practice and demonstrations from adults of both species, they muddle things and end up falling back on the A. fischeri standard, carrying things one at a time in their beak. And on top of all that, every one of them is sterile, unable to have chicks of their own.

Dilger concluded that this proved a genetic component to the nesting behaviour. It couldn’t simply be something learned from the parent bird, he reasoned, and it wasn’t for lack of learning ability. After all:

They are also favorite birds for use in trained-bird acts where they are easily taught all manner of tricks such as riding miniature railroad trains, washing clothes, posting letters, and pushing little wagons. The hybrids give every indication of being as quick to learn such behaviors.

Buckley in 1968 backed up that conclusion, reporting that for the hybrids:

there seemed to be a tendency for bill-carrying to be a last resort, after repeated rump-tucking had failed. Even so, the very next strip transport attempt would still start off with rump-tucking; each strip appeared to be approached ‘fresh’. … In both recorded and casual observations, we know of only one strip out of more than 10,000 that was ever successfully carried to the nestbox in a hybrid’s rump feathers.

Ultimately, Buckley concluded that this impairment was something of a natural backup, if a hybrid’s sterility broke down and failed to keep the two species apart. The hybrids couldn’t build a nest suitable to raise chicks in anyway, stuck between two opposing motives once they held a strip in their beak.

The lovebird studies may have been frustrating to the birds involved, but they did help shape the emerging science of behavioural genetics. Human science was just following a well-trodden path, from natural observations and Thierleben bringing a new marvel of nature to public attention, through to the less and less natural manipulations of captivity. If you’re thinking of observing lovebirds and unsure which end of that spectrum to go for—stuck between motivations perhaps—may I recommend the former? It’s less disturbing to the animals, and who knows what new wonders of your own you might see while you’re out there?

Sources: Darwin Correspondence Project, Letter no. 6235; https://www.darwinproject.ac.uk/letter/DCP-LETT-6235.xml || Darwin Correspondence Project, Letter no. 6518; https://www.darwinproject.ac.uk/letter/DCP-LETT-6518.xml || Brehm, A.E. (1878) Thierleben 2nd Edition, Volume II Part I; https://www.biodiversitylibrary.org/item/15760 || Dilger, W. (1960) The comparative ethology of the African parrot genus Agapornis. Zeitschrift für Tierpsychologie 17:649–685. || Moreau, E. (1948) Aspects of evolution in the parrot genus Agapornis. Ibis 90:206-239. || Eberhard, J. (1998) Evolution Of Nest-Building Behavior In Agapornis Parrots. The Auk 115:455–464. || Dilger, W. (1962) Behavior and genetics. In E. Bliss (ed.) Roots of Behavior. Hafner Publishing Company, New York pp.35-47. || Buckley, P. (1968) Disruption of Species-typical Behavior Patterns in F1 hybrid Agapornis Parrots. Zeitschrift für Tierpsychologie 26:737-743. || Adlersparre, A. (1938) Dimorphismus des Jugendkleides und Nestbau bei Agapornis. Journal für Ornithologie 86:248-250.

Main image credit: Bill Bouton; https://www.flickr.com/photos/billbouton/9649906942 || Second image credit: Brehm (1878) p.79; https://www.biodiversitylibrary.org/item/15760#page/101/mode/1up || Third image credit: David Hollie; https://ebird.org/species/peflov || Fourth image credit: Ngaire Hart; https://www.flickr.com/photos/eriagn/36253526083 || Fifth image credit: https://www.animal.photos/bird6/lov-pf.htm