Indirect (population suppression) control efforts


We examined reports of several of the quelea population reduction
efforts carried out in Sudan during 1978. The largest kill at nesting
sites was made by the German Technical Assistance (GTZ) team near
Sennar and south of Kosti. Their estimated kill at five sites
amounted to about 160 million quelea.

The Plant Protection Department (PPD) station at Gedaref reported the
spraying of 29 nest and roost sites in 1978, two sites by a PPD Piper
Pawnee and the remainder by Polish Antinov planes. The results, using
fenthion or Thimul as control agents, were judged by PPD to be more
than satisfactory.

Helicopters were used in population reduction operations for the first
time in 1977. The results were enthusiastically termed by PPD person-
nel as the greatest success in 15 years of spray campaigns. Losses to
the extensive millet crop produced in the Nyala area were claimed to
have been reduced by 80-90 percent for the first time in years. PPD
helicopters spent about 150 h spraying nests or roosts of quelea
located in and around thousands of feddans (1 feddan = 0.415 ha) of
millet croplands. The cost of flying time was estimated at about
$280/h (helicopter owned by PPD and flown by PPD pilots). Fenthion
was the avicide used. No information on spraying by helicopter during
1978 was available.

Large-scale operations such as these began in the Sudan in 1946 and
by 1953 in other African countries. Yet, in spite of these efforts
and the annual destruction of millions of quelea at roosts and nesting
colonies for the past 30 years, the quelea population is currently
maintaining itself at a very high and viable level. One noticeable
reason for the continued presence of quelea in Sudan is that popula-
tion control measures are annually directed at not more than 100 or
150 roost and nesting sites out of an estimated 1,000 or more such
sites in the country. If such control methods are to be truly effec-
tive in reducing quelea populations to the point that crop damage is
no longer significant, well over 900 of the estimated 1,000 roosting
or nesting sites would have to be treated. The cost of such an effort
would be astronomical.

These factors are evidence that population suppression (at least as it
is currently practiced) is not the answer to the quelea problem.

Some economic aspects

Published data on crop losses to birds in Africa are scarce. Staff of
the quelea research project are continually attempting to compile
damage assessment statistics in order to provide a proper foundation