biologia - Studia

A. KONTER
March 2005 and received its first egg on 15 April, some days after the storm. The
next nest was at a distance of 3.9 m. Nesting parameters associated with large
clutches are summarized in Table 7.
Table 7.
Summary of characteristics associated with large clutches in the Reeds
and in the Bulrush.
Clutch initiation with respect to average date for the colony
Earlier
On the average date
13 4*
Platform
Initiation Waiting time from platform to clutch Waiting time from platform to clutch
(D=decade) initiation
initiation
Below On Above Below On Above
average average average average average average
March 5 1 4 1
1D April 2 1 1
2D April 1 1
Total 6 3 4 2 1 1
* including 3 clutches laid 1-2 days prior to the average date
54
Nests with Possible Parasitic Eggs
To test the hypothesis that large-sized clutches may have been laid by more
than one female, data collected in 2005 and 2006 were analyzed with respect
irregular laying patterns (laying interval < 24 h or > 48 h) to detect possible cases
of brood parasitism.
In 2005, a Storm Night of 8-9 April reduced most of the platforms, whether
containing eggs or not, to floating heaps (Konter, 2007). 7 pairs (6 inside the Reeds and
one inside the Bulrush) salvaged at least one egg and thereafter 6 of them exhibited an
irregular egg laying pattern receiving in total a minimum of 10 parasitic eggs (9 inside
the Reeds, 1 one inside the Bulrush). Two clutches of 3 eggs and one clutch of 4 eggs
inside the Reeds were completely destroyed during the storm. The replacement
clutches initiated shortly afterwards were parasitized 5 times. One additional clutch
started immediately after the storm received 2 eggs not laid by the owners. In
summary, 9 Reed and 1 Bulrush nests contained at the end 16 and 1 parasitic eggs.
5 Reed clutches initiated in the second decade of April in 2005 were subject to
parasitism and received in total 7 eggs after a laying interruption of 3 days and longer.
In 2006, 7 early clutches in the Reed zone received each one egg after a
prolonged laying interruption (3-15 days). In the Bulrush section, 2 early nests also
received each one late egg. 3 Reed clutches initiated in the second decade of April were
subject to late parasitism and received a total of 7 eggs after laying interruptions of
6-13 days.