Page 3 - Panuccio_et_al_002

41,4 l
2002 Kurze Mitteilungen 273
Results
A total of 648 Marsh Harriers reached the north-east coast of the island from SW and S
and continued the crossing of the Tyrrhenian Sea towards NE. It was possible to estimate
586 (90.4%) adults and 62 (9.6%) juveniles ami, among adults, males outnumbered females
(348 vs 238; x'= 20.3, d.f. =l , P < 0.01). The migratory flow varied significantly throughout the
day (X' = 23.7, df = 2, P < 0.01), with the lowest proportion of individuals recorded during
the morning (Fig. 2). The strength ofthe wind had a significant effect on the migratory flow.
300
250

~ 200
..
"E
:1: 150
~
l!!
~ 100
50
... o
morning m l d day afternoon
Fig. 2: The migratory flow of the Marsh Harrier through the day over Ustica.
Abb. 2: Rohrweihenzug iiber Ustica, Aufgliederung nach Tageszeiten (vormittags, mittags, nachmittags).

Although the frequency of strong winds (> 15 km/h) was higher during each wind component
(headwind [mean direction = 71.9° ± 3.2° se): X = 9.14, d.f. = l, p < 0.01; tailwind [mean direction =
2
237.5° ± 4.8° se): x'= 4.7, d.f. =l, P < 0.05; latera( wind [mean directions = 139.2° ± 3.7° se, 319.4°
± 2.8° se]: x'= 4.46, d.f. = l, P < 0.05; Fig. 3), Marsh Harriers were seen mostly during weak winds
(wind speed below 15 kmlh; headwind: x'= 17.52, d.f. = l, p < 0.01; tailwind: t= 22.82, d.f. = l,

N=53.. N=96 "r N=36 * N=114 ** N=129 * N=394 **
100%
80%
c:
o
:e 60%
o
Q.
o 40%
...
Q.
20%
0%

H e ad T ai l Latera l
Wl NO
• strong o weak
Fig. 3: Proportion ofhours and proportion ofbirds recorded with weak (< 15 km/h) a·nd strong (> 15 kmlh)
head, tail and latera) winds (* = < 0,05; ** = P < 0,01).
Abb.3: Haufigkeit von schwachen (< 15 km/h) bzw. starken (> 15 kmlh) Gegen-, Riicken- und Seitenwinden
jeweils mit Bezug zur Anzahl beobachteter Rohrweihen.