Development of highly preferred baits for Quelea


Operational quelea control programs, involving spray applications of
parathion or fenthion on roosts and nest sites, have been in existence
for many years. Despite these widespread efforts, quelea populations
are only temporarily reduced and crop damage is generally not
affected. These marginal results are partially due to two related
problems: (1) the quelea popu action base is extremely large
(estimated to be between 109 and 10 1), and (2) quelea movement and
migration patterns are not always very predictable. More effective
reductional control of quelea might be achieved by distributing well-
accepted toxic bait at potential crop depredation sites.

The literature indicates that physical characteristics (taste, tex-
ture, size, etc.) of food items will influence acceptance by quelea.
In this experiment, two of these factors, particle size and texture,
were evaluated with small groups (n = 5 or 6) of caged quelea. The
birds were first adapted to feeding from automatic, two-choice pref-
erence testing devices. They were then exposed to different millet
particle sizes over 2- to 3-week periods. Actual preference data
were obtained during four 6-h test sessions using a weigh-back pro-
cedure. Percent preference scores were calculated by comparing the
amounts of whole and particulate millet consumed by each bird.

Results of the size preference tests are given in Table 12. Note
that all birds in the three groups preferred whole hulled millet to
ground particles. These laboratory data suggest that quelea prefer-
ence for small (0.1-0.3 mg) grass and weed seeds is probably deter-
mined by factors other than size per se (e.g., flavor, texture,
color).

In a related study, bait particle or pellet texture was examined as a
variable that could affect bait acceptance. This test incorporated
four levels of pellet hardness, achieved by mixing different moisture
levels (16, 14, 10, and 8 percent) with bentonite and mixed grain
before pelleting. The higher moisture levels produced firmer pellets.
Three independent groups of quelea (n = 6) were exposed to the pellets
in the two-choice preference devices over a 3-week period. Data were
obtained during four 6-h test sessions using a weigh-back procedure.
Percent preference scores were then calculated for each level.

As shown in Table 13, the birds were indifferent (50 percent prefer-
ence) when the harder pellets were used, but preference decreased (X =
38.0 percent) when softer (<8 percent moisture) pellets were used.
The data indicate that quelea readily accept pelletized baits when
bentonite and 10-percent or higher moisture levels are used, but low-
moisture, soft pellets are not as well accepted.