Thesis (M.Sc. (Zoology)) -- University of Limpopo, 2012 / Sparrow-larks form a relatively small genus in the family Alaudidae and comprise
only seven species distributed widely throughout Africa and parts of the Eurasian
landmass. Sparrow-larks are unique amongst larks in that they are sexually
dichromatic and exhibit biparental care. The chestnut-backed sparrow-lark
Eremopterix leucotis is endemic to Africa with five subspecies recognized based on
differences in plumage colouration. The five subspecies are distributed throughout
the arid to semi-arid savannas of Africa with two subspecies (E. l. hoeschi and E. l.
smithi) occurring in southern Africa. Despite their widespread occurrence and its
interest for research on the evolution of characteristics in the family (e.g. being
sexually dichromatic and exhibiting biparental care), very little is known of the biology
and ecology of the Eremopterix larks. The chestnut-backed sparrow-lark is no
exception and most of what we know of the species is based on incidental
observations from a few nests. In an attempt to improve our knowledge of this
interesting group of species, it was decided to study various aspects of the breeding
biology and ecology, moult, vocalizations and geographical variation in the chestnutbacked
sparrow-lark.
The breeding biology of the chestnut-backed sparrow-lark was studied at Al3 farm
(De Loskop) near Mogwadi in the Limpopo Province of South Africa from January
2008 to December 2010. Data collected during the study included: breeding
seasonality, egg and clutch characteristics, duration of the incubation and nestling
periods, nest-site characteristics, the roles and relative contribution of the sexes in
the breeding cycle, nestling development, diet and nestling provisioning rate, and
breeding success. Chestnut-backed sparrow-larks bred mostly during the dry
season, which is from April to September in the study area. Nevertheless, the results
revealed that breeding is bimodal with a main peak in breeding activity in late
summer and autumn (March to April) and a second smaller peak in spring
(September to October). The species showed geographical variation in clutch size
with a mean of 1.88 eggs recorded in the study area as opposed to 1.00 recorded in
the northern parts of its range. Egg dimensions compared well with measurements
obtained from the Nest Record Card Scheme of the Animal Demography Unit,
University of Cape Town, South Africa. The mean incubation period of 10.33 days
recorded in this study compares favourably with that of other Eremopterix species
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(8–10 days), a genus with some of the shortest incubation periods amongst larks.
The mean nestling period of 9.2 days (range: 8–10) in the study area was
significantly less than the 10–12 days reported for populations in the northern range
of the species, but it compares well with those of other sparrow-larks.
Nest site characteristics, which were quantified within a 1 m2 quadrant with the nest
as the centre, including nest dimensions, were consistent with those reported in the
literature. Chestnut-backed sparrow-larks in the study area preferred to nest in areas
with a high percentage of bare ground (median = 67.5%) and very little vegetation
cover (median = 25%). Most nests faced in a southerly direction compared to nests
in the north of the species’ range, which face in a north-easterly or easterly direction.
The species’ preference to face the nests away from the midday sun most probably
serves a thermoregulatory function to avoid excessive heat during the warmest parts
of the day. Most nests (78.2%) had an apron varying in size from small and
insignificant to large and well-developed. The functional significance of the apron
remains a matter of conjecture and there was no association between breeding
success and presence or absence of the apron. In addition, one pair constructed one
nest with and another without an apron, suggesting that individual preference or
characteristic is not a determinant factor in the construction of an apron. Both sexes
took part in nest construction, incubation and feeding and brooding of nestlings.
However, the relative contributions were not entirely symmetrical as males incubated
a greater proportion (50.1%) of the time compared to females (43.1%), and the mean
and median of male incubation shift lengths were longer than that of females, albeit
not statistically significant. However, females made statistically significantly (P <
0.05) more nest visits to deliver food compared to males (54.6% vs. 45.5%). The
average breeding success, estimated using Mayfield’s method, was 16.1% but there
were inter-annual differences with the overall breeding success in 2010 being only
8.1% compared to 20.6% of 2008. Known causes of failure included nest
depredation, flooding, starvation, nest abandonment and hatching failure.
Statistical analysis of morphometric data of live specimens and museum study skins
suggest that, in addition to being sexually dichromatic, chestnut-backed sparrowlarks
also exhibit mild sexual size dimorphism. However, there was considerable
overlap in these measurements between the sexes and as a result the biological
significance of this sexual size dimorphism may be negligible. Nevertheless, the
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results show chestnut-backed sparrow-lark males tend to have longer wings and tails
compared to females. This may be adaptive with respect to the extended display
flights that males perform during the breeding season. Interestingly, the mean mass
of breeding females in the study area was significantly more compared to males,
whereas the SAFRING database, representing data recorded throughout the year,
showed no significant differences in the mean mass between the sexes. The greater
mass of breeding females may relate to physiological changes associated with the
acquisition of resources and the development of structures and tissues associated
with egg-laying and egg-production.
Larks rely heavily on vocalizations to attract mates and advertise territories. Not
surprisingly, the study revealed a rich vocal repertoire for the chestnut-backed
sparrow-lark. The analysis of the vocalizations shows that chestnut-backed sparrowlarks
have a display song performed by males, a sub-song sung by both sexes and
various different calls used in different contexts, e.g. flight and alarm calls. The study
also presents the first analysis and description of the vocalizations of nestlings. An
interesting feature of the vocalizations of the chestnut-backed sparrow-larks was that
they performed hetero-specific vocal mimicry, which was incorporated in the subsong.
Moult is a relatively unknown aspect in the annual cycle of the majority of larks.
Chestnut-backed sparrow-larks undergo post-breeding moult, which is an adaptation
to reduce the conflict between moult and breeding as both activities have high
energy demands. The moult study also showed that they undergo a partial moult in
mid-winter, involving the inner-most secondaries and some of the contour feathers.
The results of this study shed valuable light on the natural history of this species and
contributed significantly to ornithology and our growing understanding of the biology
and ecology of the family. The results can also form a basis for future inter- and
intraspecific comparative studies. The study illustrates the importance of undertaking
long term studies of species to account for inter-annual differences in various
ecological parameters.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/812 |
| Date | January 2012 |
| Creators | Dikgale, Mahlodi Lucket |
| Contributors | Engelbrecht, D. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xviii, 134 leaves : ill. (some col.) |
| Relation | Adobe acrobat reader, version 7 |
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