biologia - Studia

PLATFORM INITIATION, CLUTCH INITIATION AND CLUTCH SIZE IN COLONIAL GREAT CRESTED GREBES
Inside the Bulrush zone, comparisons were difficult due to the limited
amount of data and the generally lower nesting density, and the results have to be
considered with care. In all years, non-clumped nests held more eggs than nests
clumped at degrees 1-2. In 2003 and 2005, higher degrees of clumping resulted in
increasing average clutch sizes. In 2006, a gradual decline of clutch size with
increasing degrees of clumping was noted, and this trend was exactly opposite to
the evolution inside the Reeds in the same year.
The pattern of clumping for the colony as a whole was similar to that for
the Reeds, with no uniform pattern for the four-year period of this study. One-way
ANOVA testing of the evolution of clutch size in relation to the degree of clumping
performed for the colony as a whole nevertheless proved significant differences in
clutch size for 2006 (P4 --- --- --- --- ---
Colony 0 4.00 ± 0 (3) 4.33 ± 0.50 (9) 4.00 ± 0.94 (10) 3.75 ± 0.46 (8) 4.03 ± 0.67 (30)
1-2 3.57 ± 0.94 (23) 3.88 ± 0.67 (25) 3.94 ± 0.85 (31) 3.62 ± 0.59 (21) 3.77 ± 0.79 (109)
3-4 3.78 ± 0.88 (45) 3.86 ± 0.85 (21) 4.21 ± 1.17 (29) 4.22 ± 0.88 (23) 3.98 ± 0.96 (118)
One-way
ANOVA
>4 3.89 ± 0.69 (38) 4.07 ± 0.65 (29) 4.20 ± 1.41 (25) 4.42 ± 0.98 (38) 4.15 ± 0.96 (130)
F- value 0.8 1.3 0.4 4.7 3.3
df 3, 105 3, 80 3, 91 3, 86 3, 374
P 0.47 0.28 0.75 0.005 0.019
Tukey test Periods that
differ (P)
2-4 (