Dilger crossed Peached-faced Lovebirds
A. roseicollis, which tuck numerous strips
of nesting material into the feathers on the
rump or back, with Fischer’s Lovebirds
A. fi scheri, where the females carry single
nesting items in the bill. (Despite being
considered separate species, the two
are capable of reproducing in captivity
but, as we will see, the resultant hybrid
offspring have reduced fi tness and would
not successfully breed in the wild). The
hybrid offspring, having inherited a mix of
genes for each distinct behaviour end up
displaying an unsuccessful compromise
between the two. Hybrid females try to
tuck materials into their feathers, but
fail dismally. A. roseicollis females are
able to succeed at this task innately, but
the hybrids don’t realise they need to
release strips once they tuck them in, so
end up pulling them out. Even strips that
do get tucked in are insecure and fall
out. (Hybrids tuck them into the wrong
feathers). They also grasp the nesting
materials inappropriately; tend to get
distracted and instead engage in preening
activities, get a drink or headscratch; may
try and tuck inappropriate objects such as
twigs, which are bill-carried by A. fi scheri,
but never used by A. roseicollis, into the
feathers; and will even end up running
backwards in their bid to get their bill
closer to their rump! Hybrids that abandon
tucking and instead carry materials in
their bill do a little better, but are never
as profi cient as pure A. fi scheri females
which are aces at carrying material in the
bill due to the behaviour being encoded
in their genes. Hybrid females need to
learn how to carry the materials in their
bill. Dilger found it took three years—one-
third of a lovebird’s lifespan—for a hybrid
to successfully carry nesting materials
and reduce performing irrelevant or
inappropriate behaviours. That hybrids
inherit partial behavioural repertoires
from each parental species suggests that
this behaviour is polygenic (infl uenced by
many genes).
Buckley (1968) also noted a number
of disruptions in nesting behaviour in A.
fi scheri and A. roseicollis hybrids, including
that, unlike males in pure species pairings,
hybrid males would interfere with female
attempts to gather nesting material. If eggs
were laid, the female displayed aberrant
behaviour, covering the eggs with nesting
material and failing to incubate them.
Due to the importance of courtship
and nesting behaviours in reproduction,
differences between species would be
isolating mechanisms, reducing the
occurrence of successful interbreeding
between different species and reinforcing
their distinctness, even when species co-
occurred in the same area. The disruption
of these important behaviours in hybrids—
as well as sterility, which often occurs in
crosses except for those between species in
the periophthalmic group—reinforces the
separation of species as distinct entities.
INTERBREEDING
The ability of Agapornis species to
interbreed is often considered a boon for
lovebird breeding fanciers because colour
mutations can be introgressed easily into
different species, provided the hybrid
offspring are fertile. However, as explained
above, some of these couplings may result
in maladapted offspring.
Consistent with the phylogeny of
Agapornis, the species within the most
closely related periophthalmic group
readily hybridise, and will hybridise less
readily with A. roseicollis. The latter
hybridisations often lead to lower nesting
success. The resultant hybrid offspring are
fertile except for A. personata with
A. roseicollis or A. lilianae, and
A. lilianae with A. fi scheri. Hybridisation
between the sexually dimorphic group
is rare.
Interestingly, female A. roseicollis x
A. fi scheri hybrids when presented with a
choice of purebred males of each parental
species, as well as hybrid males, always
choose to pair with hybrids. Nevertheless,
in all cases, even with hybrid males
exhibiting more vigorous precoplatory
displays, hybrid females are less
responsive than purebred females.SPECIES RECOGNITION
Despite the clear innate genetic role in
nest-building behaviour, species recognition
is largely a learnt behaviour. This has
been demonstrated by cross-fostering
experiments. The natal down of the Grey-
headed or Madagascar Lovebird Agapornis
canus, the Abyssinian or Black-winged
Lovebird Agapornis taranta, and Red-
headed Lovebird Agapornis pullarius is
grey, whereas it is red for the other more
derived lovebird species.
If a female has experience raising her
own brood, she will reject a cross-fostered
chick with natal down of a different colour.
But if an egg of such a chick is placed in
the nest of a lovebird’s fi rst clutch, she will
raise it alongside her own. Moreover, if this
aberrantly coloured chick hatches fi rst,
before her own chicks, she will reject her
chicks. For example, Dilger found that if
an A. roseicollis has her fi rst experience of
motherhood with the newly hatched chick
of the grey natal down coloured A. canus,
she will rear it and then refuse to raise any
of her own offspring.
That mate recognition in Agapornis is
strongly infl uenced by imprinting (refer
to my previous article, ‘Imprinting—how
a chick learns its identity’, Australian
BirdKeeper. vol. 27, no. 4, pp. 226–237) is
supported by the fact hybridisation can be
facilitated through cross-fostering. When
an egg of one species is raised in the nest
alongside the clutch of another species, the
bird will pair with a member of the species
it has been fostered with.STUDIES IN THE WILD
As noted previously, almost all that isknown about lovebird breeding and nest
behaviour has been obtained from studies
of captive individuals. While certainly
valuable, it is important to discover
whether such behaviours occur under
natural conditions. Given the fundamental
importance of breeding behaviour,
understanding breeding biology in the
wild is important from a conservation
perspective. Most information from wild
lovebirds is anecdotal. Just two species
have received proper scientifi c studies, and
only recently.The status of Black-cheeked Lovebirds
Agapornis nigrigenis is Vulnerable on the
IUCN listBlack-cheeked Lovebird
A study published in 2005 by Warburton
and Perrin was the fi rst to properly provide
detailed data on the nesting biology of
the Black-cheeked Lovebird Agapornis
nigrigenis in Zambia. This species,
labelled Vulnerable, has a very restricted
geographic range of just ~2500km sq,
and is strongly associated with Mopane-
dominated woodland where daily access
to water is available. A. nigrigenis belongs
to the nest-building periophthalmic group
and was found to nest exclusively in
naturally created cavities in Mopane trees.
Fortunately, cavities form readily in these
trees and thus nest sites were not limited.
Consistent with the gregarious nature
of these parrots in captivity, A. nigrigenis
was found to nest colonially, with nest
sites showing a clumped distribution.
Only one nest was recorded per Mopane
tree, but whether this was due to some
territoriality, or because only one cavity
per tree was available, is unknown.
Colonial nesting is likely facilitated by the
fact nesting sites are not limited, since
not only are there ample cavities but, as a
nest-building species, A. nigrigenis is able
to modify otherwise unsuitable cavities.
Nest structures varied. Some were an open
cup, others had a half-roof structure, while
others had the complete domed structure.
Nests were created out of intricately
woven Mopane petioles (95% of nesting
material), with a relatively rough texture.
The insides of the nests were lined with
feathers, leaves, bark and grass.