| dc.description.abstract | Birds of the family Columbidae (Doves) and the
family Ploceidae (Weaver-birds and Sparrows) are
known to destroy cereal crops in many parts of
Kenya. About KSH. 30 million worth of grain are
lost to birds annually in the country (F.A.O. 1981).
The Red-billed Quelea Quelea quelea (L.) is the
principal bird pest of cereal crops and many studies
have been carried out on its biology, pest status
and -control in eastern Africa, especially by the
F.A.O's Regional Bird Control Project. However,
there has been no comparative study into other
bird species that cause localised damage to
small-scale cereal crops, epecially in the
semi-arid areas of Kenya. I
2. This study concerned the populations, the breeding
biology, the food and the nest- status of the
following bird species in the Kibwezi area of
Machakos District:
A Red-eyed Dove Streptopelia semitorquat~
B Ring-necked Dove " capicola
C Laughing Dove " senegalensis
D Emerald-spotted Wood Dove Tur tu r chacospiios
E Wpite-browed Sparrow Weaver Pl ocepasser mahali
F. Grey-headed Sparrow Passer griseus
G Masked Weaver Ploceus intermedius
H Chestnut Weaver Ploceus rubiginosus
I Red-billed Quelea Quelea quelea
The research was carried out during the period
between July 1979 and July 1981; and mainly in and
around the small holdings at:Masalani, 20 km northeast
of Kibwezi.
3.. All the columbid species were resident at Masalani
but the Red-eyed and the Ring-necked Doves made
local movements in the area. The population
densities of doves in cultivated and the uncultivated
areas were high during the period between January
and July principally due to breeding in the area.
The Chestnut Weaver and the Red-billed Quelea
were abundant during the period between October and
February due to an influx of adult and the
immature birds probably bred in Tsavo East National
Park. The White-browed Sparrow Weaver, the Greyheaded
Sparrow and the Masked Weavers were resident
and bred at Masalani. The peak population densities
of those species were recorded between May and July,
primarilydue to breeding.
4. Except for the Chestnut Weaver and the Red-billed
Quelea, the rest of the ploceid and the Columbid
species bred at Masalani during the period between
March and July. The columbids bred intermittently,
with the breeding activities being greatly reduced
during the period between August and October. The
status of the breeding habitats profoundly influenced
the breeding success of the individual bird species.
All the seven bird species that bred at the site
fed their young with soft seeds of cereals and
sunflowers. After breeding, both the adults and
the immatures dispersed locally, probably to reduce
the competition for food.
5. The principal food of the doves consisted of
forb seeds and small fruits of woody plants.
The seeds of annual grasses formed a notable
proportion of the annual diet of the Laughing
Dove only. Seeds of sorghum and sunflowers were
consistently found in small proportions in the diets
of the" Ring-necked and the Laughing Doves. However,
the seeds of cultivated Elants were generally not
important in the annual diets of the Columbid species.
The seeds of forb plants were as important as the
grass seeds in the diets of the White-browed Sparrow
Weaver, and Grey-headed Sparrow. The Masked Weaver
was more of a frugivore than a granivore, with the
bulk of its annual diet principally consisting of
fruit berries of shrubs and trees. Both green
and dry seeds of grasses, especially the annual
grasses, were the dorminant components of the
diets of the Chestnut Weaver and the Red-billed
Quelea. The seeds of the cultivated plants were
important in the diets of both the columbid and
plopped species when those seeds were available in
the fields.
6. The abundance of birds and consequently their
biomasses in the cultivated areas was closely related
to the status of the crops and the availability of
the crop seeds in the preferred form. The Red-eyed
and the Ring-necked Doves preferred the ripe seeds
with a high moisture content. The Laughing and
the Wood Doves preferred the dry seeds, and mainly
foraged for them on the ground. Except the Whitebrowed
Sparrow Weaver and the Grey-headed Sparrow
which showed preference for the dry seeds, the
rest of the plopped species preferred the green
seeds. The bird species that preferred to feed
on the green seeds were responsible for the
bulk of the crop damage.
7. The losses of grain c~ops and sunflowers-to birds
at Masalani were much more seasonal than the damage.
The losses of different crops to birds were on
average: Bulrush millet (45%), Maize (1.5%), Sorghum
(12%) and Sunflowers (8%) per year. Whether these
losses are typical of other years and other semi-arid
areas is not known. However, this study has shown
that both Bulrush 'milletand Sorghum are under threat from
Chestnut Weavers, the Masked Weaver and the Red-billed
Quelea. The doves, especially the Red-eyed and the
Ring-necked Doves, pose ~...a threat to sorghum and
sunflowers. Further, this study has shown that the
cereal crops that ripen in January and February
are in greater danger from the migrant bird species
than those that ripen in May and June. The
sunflowers that ripen in February are comparatively
safe while those ripening in June are in danger
from the big numbers of doves and the Grosbeak
Weavers Amblyospiza albifrons.present during
the period.
8. In conclusion, it is apparent that the seasonality
of the climate especially rainfall in the Kibwezi
area, imposes a considerable seasonality on the <,
bird populations. The losses of the farm crops
to birds ,also vary seasonaly and closely relate
to the periods of abundance of the birds in the
area. Both the resident and the non-resident bird
species cause substantial losses of grain
annually and pose a threat to the production
and the development of grain crops and sunflowers.
The situation is likely to be so in other semiarid
areas of Kenya. | en |
