by Ursula Bryson
In a discussion with another bird ringer the question arose, how to determine the gender and age of Rosy-faced Lovebirds. Breeders can rely on genetic testing to determine the sex of Rosy-faced Lovebirds, but bird ringers? We never had enough guidance and confidence to do so.The standard literature remains vague about the differences. We were astounded how very little information
exists about the species in the wild. More concrete information can be found in breeding manuals or reports from the laboratory (Dilger 1960) which result from long term daily observations. Is a valid distinction possible by the colouration of the plumage? Are there other reliable criteria, when you watch a bird or have it in the hand just for a few minutes? Extensive study of the specific literature and interchange with breeders, researchers and geneticians confronted us with an unimagined complexity, and as always, we were left with more questions than before.
Sexing of Rosy-faced Lovebirds in their habitat
It is the behaviour that best tells the sexes apart: In the event of breeding, only the females build the nest and will sit on the eggs (the latter at least in captivity). It is they who carry sticks, grass, strips of bark and other nesting material to the nest. This is done by tucking it under the feathers of her rump and lower back (Forshaw 1989), while the male might prepare nest material but would not deliver it to the nest (Schwichtenberg 1973, p. 56). In captivity, same sex pairs have also been observed, especially in young birds or when a partner of the other sex is not available (Dilger 1960, p. 667). Does this occur also in the wild?
And the plumage?
Described as pale grass green, slightly darker above with bright blue rump, peach pink face and upper chest, and darker reddish crown, it shows a substantial variation in its plumage colouration. When two birds sit together, as pairs often do to preen each other, it is said that the slight sexual dimorphism can be observed: The pink of the head of the female is described as paler Lanioturdus 54(1) Page 14 March 2021 and to less extensive (Schwichtenberg 1973, p. 15). On suitable pictures such plumage differences become visible. Alas, I learned by talking to breeders, curators, geneticists and ornithologists that these criteria give no definite certainty of the evidence of gender.
Cheeks and eyes
You find a grey area of variable extent behind the pinkish cheeks in both sexes. Rosy-faced Lovebirds do not present white skin around the eye, as depicted in some of the literature, but just a thin ring of tiny white feathers around bare pale skin. They are thus unlike the group of “Agapornidae with white eye-ring”, which includes the Yellow-collared Agapornis personata, Fischer´s A. fischeri, Black-cheeked
A. nigrigenis and Nyasa (Lilian’s) Lovebird A. lilianae. These four species, esteemed by breeders, are
wide spread as pets and escapees have established feral populations in some cities of South Africa, where they easily interbreed with escaped or released Rosy-faced Lovebirds.
Face and chest
The extent of the rosy colour in some individuals reaches down from the face to the chest and diffuses into the green while in others it terminates in an almost clear line slightly below the throat. Is this a consistent feature for sexing? Again, no conclusive determination of sex is possible through this criterion.
Shades of green
The body and the wings of some individuals seem to be almost uniformly coloured, while others display a clearly contrasting darker colouration of wing and back compared to the flanks and underparts. Looking through hundreds of pictures of wild birds, for plumage colour and moult features, beak colour, “tooth” shape and abrasion, quality of cere and the dorsal part of the bill, among others, the question arises, whether the darkening might be a sign of age. This also includes the rump becoming a darker and deeper blue. Or are the contrasting colours of upper- and underparts an expression of the so-called “dark factor”, a genetic disposition, which then shows more clearly in adult birds?
A precise description of the nestling and juvenile plumage is missing. In the literature, it is called vaguely “as adult”, with paler or duller colouration in the rose parts (Fry et Lanioturdus 54(1) Page 16 March 2021 al. 1988; Perrin 2005), only Radtke (1984, p. 39) describes it as “similar but paler in all colours”. More research is needed for the detailed documentation of the colouration of juvenile plumage, considering also the aspects of dark (and other) genetic factors, of escapees and of the influence of possible hybrids. After a complete post-juvenile moult the plumage turns into a light green. We were wondering, whether in more mature birds the wings become even darker, or whether – again – the dark factor is showing.
And then
We have, though, to take into consideration, that a genetic “dark factor”, even in wild Namibian birds, has been observed which might show in a plumage of visibly darker or olive-green colour variation (van Den Abeele, pers. comm. 2020). And some individuals show brighter colours than those of their group. More research is needed to understand these variations in the wild. Other genetically based colour variations have been found in the wild, like yellow or turquoise, though rarely. (See an overview of the recorded lovebirds of different species in van der Zwan et al. 2019). In February 2019, three different coloured juveniles of the same age (clutch?) were photographed in Henties Bay. The genetic lines areLanioturdus 54(1) Page 18 March 2021 determined by dominant, recessive and co-dominant genes, thus variations of siblings in the same brood are possible.
In the hand
The birds caught for ringing are mostly not recognizable as belonging to a distinct partner. Thus the possibility of comparison between two wild birds of a pair is rare. In the literature we find that wing and tail are slightly longer in males, taken from a small sample of 7 males and 8 females, the beak length from the cere to the tip is equal in both sexes (Fry et al. 1988, Vol. 3, p.18), while females, at least observed in captivity, tend to be slightly larger than males although this difference is not apparent to the eye and is only reflected in average weights (Dilger 1960, p. 654).
Mass
For the field work, the mass alone as a sexing criterion seems questionable, as the birds in the wild are subjected to most variable conditions. Drought or rainfall with subsequent changes in food supply, differing habitat such as sub-desert steppe, farmland with crops and waterholes or cities with constant food on offer will affect the physical fitness and mass. While Dilger (1960, p. 651) records for captive birds 55,4g for males (18) and 56g for females (20) (presumably these data are given in Forshaw (1998): 55,4 (18 male), 56 (24 female) and then quoted in Hockey 2005), Fry et al. (1988) give for 29 unsexed, presumably wild, individuals 46 to 63g with a median of 54g. Out of 223 (except for a very small number) unsexed individuals, which we recorded over a period of more than 15 years in different areas of Namibia, the range was quite comparable to these data with 44 to 67,3g with a median of 52,4g. The question of gender cannot be answered by the mass considering the small difference and the number of variables. And big males and small females may occur.
Beak
The beak of the female is said to have a wider base than in males. The head of the female is also more rounded than that of the male which is more massive and angular (Schwichtenberg 1973, p. 15). I could not find published measurements, nor photos depicting clearly these specific features. It might be of interest for ringers in the long run to include in the collected data those of the size of the head and the base of the beak.
Pelvic bones
Breeders recommend to check the gender by the pelvic bones with the bird in the hand (de Grahl 1990, p.140), if genetic testing is not possible. After sexual maturity the position and form of the pelvic bones are palpably different between the Lanioturdus 54(1) Page 19 March 2021 sexes. In females, these bones are mostly stronger, rounded and a few milli-meters apart. Those of the males appear weaker, more pointed and quite close to each other (Schwichtenberg 1973, p. 45). Sexual maturity has been observed in one single male at about 80 days (Dilger 1960, p. 635). This has been recorded in the literature as the first breeding age. “However, most birds begin to behave sexually at a considerably later date; usually after the post juvenal moult is complete at about four months” (ibid.). The technique of checking on the pelvic bones is being applied in other birds such as raptors or galliformes. As ringers we would need some basic guidelines for this method. The distanced position of the pelvic bones in females leads to a sitting posture where legs are further apart than in males (de Grahl 1990, p.140). Due to a number of circumstances (landing, movement, position) this can be used as only one sexing criterion of many.
Colours
To make things even more interesting, the colouration of Rosyfaced Lovebirds may depend on different factors like the freshness or the bleaching and wear of the plumage and genetically based colour variations. Rosy-faced Lovebirds are valued easyto-breed pets with several broods possible per year in captivity, a fact that protects the wild populations from a wider persecution for trade. For breeders “beautiful” birds are more attractive as they get higher prices on the market. “Beautiful” means in this context colourful or exquisite and rare colouration, like yellow, turquoise and blue and others, similar to Australian Budgerigars Melanopsittacus undulatus. These colour forms occur in the wild, although very rarely. In the recent decades, the number of Rosy-faced Lovebirds escaped fromaviaries seem to have risen and numerous individuals have been regularily sighted out of their natural range. Feral populations have spread not only in cities in southern Africa, mainly in the area of Johannesburg and Pretoria (Symes 2014, p. 239; SABAP2), but can be found on all suitable continents, including in several European countries around the Mediterranean, and in other areas (Collar and Boesman 2020, see world map). The species thrives especially well in the USA, mainly in Arizona, with numbers estimated at over 2,000 (Audubon Field Guide 2020; Corman 2005). As obvious descendants from aviary birds, there is a huge colour variation in the now wild living birds. Other Agapornidae have started feral populations around the globe and interbreed easily with Rosy-faced Lovebirds. It seems that the newly established and growing populations in Namibia belong mainly to natural populations which have benefitted from increasing water availability in the arid areas through farming, and from increasing man-made structures for nesting (C. Brown, pers. comm. 2020).
References
Audubon Society 2020.
https://www.audubon.org/fieldguide/bird/rosy-faced-lovebird.
Collar N, Boesman PFD 2020. Rosyfaced Lovebird (Agapornis roseicollis),
version 1.0. In: del Hoyo J, Elliott A,
Sargatal J, Christie DA, de Juana E
(eds). Birds of the World. Cornell Lab
of Ornithology, Ithaca, NY, USA.
https://doi.org/10.2173/bow.peflov.
01 .