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Short-eared Owl Asio flammeus demographic trend
and ecology from the data of the Italian raptor centers (C. R. R.
Centri di Recupero Rapaci)
Marco Mastrorilli * Luciano Festari ** * via Carducci 7 Boltiere (BG)
24040 flammeus@libero.it ** via
S.Antonino 12 Capergnanica (CR)
The importance of the raptor centers (C.R.R. Centri di Recupero Rapaci)
in the study of the Short- eared Owl ecology has been pointed out by Clark
(1975); they play an important role in the conservation of the species
and in its demographic fluctuations. In the Mediterranean Basin, the Short-eared
Owl undergoes cyclic fluctuations and nomadism. These processes are typical
in the Holarctic region (Mikkola, 1983; Hoyo J.et al., 1999), although
its dynamic is not well known to date.
Materials and methods
19 raptor centers have been contacted. They gave the following data about
74 Short-eared Owls treated between 1982 and 1999: date and place of provenance,
cause and result of their stay, diseases. As in Clark (1975), we selected
the data about the Short-eared Owls (53 in number) treated during the
post-breeding period, and in winter i. e. from September to February (Table
2).
Results and discussion
In the 18 years' span considered, the number of birds shows no negative
trend; irregularities are likely to be related to cyclic fluctuations
occurring in Northern Europe. The high number of Short-eared Owls found
in the post-breeding period correlate with a census of Short-eared Owl
breeding territories carried out in Finland between 1986 and 1996 (Saurola,
1997). In 1989 and 1996, Saurola found the highest values. In the same
years, in Italy, peaks have been recorded in the raptor centers (Table
2): 35.8% of the data cover these two years. Also in 1991, a strong convergence
between the Finnish occurrences and the Italian ones took place, both
showing a significant peak (15%).
ANNI
DI RECUPERO |
82 |
83 |
84 |
85 |
86 |
87 |
88 |
89 |
90 |
91 |
92 |
93 |
94 |
95 |
96 |
97 |
98 |
99 |
ASIO FLAMMEUS |
3 |
2 |
1 |
1 |
4 |
6 |
3 |
11 |
4 |
10 |
1 |
2 |
4 |
6 |
10 |
2 |
2 |
2 |
Table 1. Short-eared Owls treated during the whole year
POST BREEDING
SEASONS |
82 |
83 |
84 |
85 |
86 |
87 |
88 |
89 |
90 |
91 |
92 |
93 |
94 |
95 |
96 |
97 |
98 |
99 |
ASIO FLAMMEUS |
3 |
1 |
1 |
1 |
4 |
1 |
3 |
12 |
4 |
8 |
1 |
2 |
1 |
1 |
7 |
2 |
1 |
1 |
Table 2. Short-eared Owls treated during the winter and post-breeding
period.
The poor knowledge of migratory fluxes and the marked nomadism of the
species stress the importance of a confront between Nordic demographic
cycles and occurrences in the wintering areas. The data about diseases
and wounds affecting the Short-eared Owls treated in the centers turned
out to be different from the ones which usually characterize the other
Strigiformes. An high percentage of bullet wounds have been found (64.5%);
this is unusual for nocturnal raptors, which are not threatened with poaching
(Penteriani, 1992; Di Pietro et al.,1998; Fraissinet et al., 1999). Collisions
with vehicles also cover an high percentage (25.8%). These anomalies are
to be related to the Short-eared Owl habits, the bird being not so crepuscular
as the other Strigiformes and frequenting open areas. The dispersal of
the Short-eared Owl in areas bordering on Italy (Michelat & Giraudoux,
2000; Leskovar, 1999) accentuates the importance of the raptors centers
- also as potenial shelter for nestlings -. Better and closer relationship
with Italian and foreign raptor centers and between them is advisable.
References
Clark R.,1975. Wildlife Monographs 47:1-67
Di Pietro A., Mastrorilli M, Pavesi C., Sangiovanni M.1998. Pianura 10:19-26
Fraissinet M., Di Giacomo G., A.Lenza, R.Lenza, 1999. Picus 47:27-34
Hoyo J., Elliot H., Sargatal J. 1999. Vol.V Ed. Lynx, Barcelona
Leskovar K.1999. Larus 47:125-126
Michelat D., Giraudoux P.2000. Rev Ecol. (Terre vie) 55:77-92
Mikkola H.,1983. Poyser London
Penteriani V.1992. Serie WWF 9:13-14
Saurola P.,1997. USDA Forest Service General Technical Report NC 190:363-380
Acknowledgements
We thanks P. Galeotti for his help. The also thanks the following
people for the data given: A.Rossi (C.R. Malbe), N.Savini (C.R.R.PE),
S.Piciocchi (C.R.R. WWF Astoni), R.Lenza (C.R.R.WWF Serre Persano), L.Cattini
(C.R.R.Lipu PR), G.Memeo (C.R.S.Puglia), M.Fraissinet, C.Bertarelli, D.Michelat,
A.Dembech (Lipu FG), C.R.F.S. LIPU Roma, G.Premuda (Lipu BO), A. Fagan
(C.R.VI), S. Raimondi (C.R.R.WWF Vanzago), M. Canziani (Lipu MI), P. Paolillo
(WWF Calabria), A. Marinelli (C.R. WWF Bosco Palo), C. Pavesi (C.R.R.
WWF Crema).
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