Presence on alps

Viene presentato uno studio che evidenzia la presenza e la nidificazione della Civetta Athene noctua in ambiente alpino, in un comprensorio della Val Brembana in provincia di Bergamo. Viene inoltre segnalata la nidificazione di Civetta più elevata riscontrata in Italia.

In this study, there are many informations about presence and breeding of the Little Owl Athene noctua in Orobie Alps (North of Italy, Lombardia, Bergamo district).

Little Owl Athene noctua is a Strigiformes of prevalently sedentary habits (Mikkola H.,1983, Juillard M., 1985, Genot J.C.,1989) which locally makes short wanderings and vertical migrations, especially during winter and autumn.

In Europe, in particularly favourable conditions, it reproduced even in hill and mountain places and, sometimes, these events were deeply studied (M. Juillard et alii, 1990, M.Vogrin,1997).

In Italy, Little Owl is very common and well distributed on the plain and on the hills, usually not over 500 m. above s.l. (Casini L. in Meschini E. & S.Frugis, 1993, Brichetti, 1999). However, reproductive places were found on the mountains: in Liguria and Piemonte, just over 1000 m. (Andreotti A. in A.A.V.V., 1989, Mostini L. in Mingozzi et alii, 1988).

Demographic trend of Little Owl was studied during last years in Bergamo district (Lombardia), but researches are limited to plains (Mastrorilli M., 1997, 1999a, 1999b).

In the past the presence of Little Owl was observed in he lower part of Taleggio Valley (Perugini F., 1991) but there was no evidence of possible reproductions.

Bergamo district is a territory composed for more than 50% by hills and mountains with summits over 3000 m. This mountain territory is part of the geological area called Southern Alps and, in particular, these mountains are known as Orobie Alps.

The deeper valley of glacial origin is Brembana Valley, characterized by a valley furrow of many kilometers, originated by the downflow of Brembo river running in a deep river-bed and surrounded by rocky sides (Dolomia and Calcareous Rocks)and moist and wooded slopes.

In confluence areas with little side-valleys and small affluents, Brembana Valley gets larger and these spaces were occupied by mankind which created centres of a certain imortance (Zogno, S. Pellegrino, S. Giovanni Bianco). S. Pellegrino is the most important one, a well-known spa.

Along rides, the abndace of woods offers spaces to natural terraces which originated glades and pastures suitable for Little Owls.

On the contrary, the mouth of Brembana Valley offers a situation of difficult penetrability: the river impetuosly flows in its river-bed, surrounded by very close mountains which do not allow avifauna to easy pass through. Moreover, during last years the building of many roads with big galleries and viaducts ruined the original environment and created a sort of artificial barrier, so now this valley is more impenetrable.

As for termic phenomenon, it is very important to point out that in winter the shaded parts are subjected to harsh temperature (often under thermic zero), while in summer humidity of woods and of the numerous streams offer tipically alpino conditions.

This study lasted for three years (1997-99) and gave the possibility to survey interesting presences and habits of Little Owl, sometimes very surprising in relation to our knowledge.

We made many studies with play-back method, completed by data of other ornithologists and also evaluating rescue of wild avifauna by Lipu (Italian League of Birds Protection) Bergamo.

At the end of this research two reproductive places were discovered, together with five territorial zones (play-back method).

Besides ealuating the effective distribution of the species in this alpino valley, we tried to discover the migratory way to the colonization of Brembana Valley.

This is the first Italian study which deals with the relation between the presence of Little Owl and the alpino environment, while in other alpino areas, during the preparatin of regional atlas, the presence at high altitude was excluded (Bordignon, 1992).

The most important result was the finding of two reproductive places, one at the highest altitude in Italy (1230 m.), in Val Taleggio, Loc.Quindicina.

The nest, discovered in June 1999, let us support by documentary evidence the nidification of the species in an alpino pasture over 1000 m., in a particularly sunny area, south-east exposure. Three Little Owl nestlings were found in a desrted alpine hut which was near a beech wood. In the same area the presence of Tawny Owl Strix aluco and even of Tengmalm's Owl Aegolius funereus was previously poited out.

This nidification showed a great penetration of Little Owl in Brembana Valley (20 km. far from the plain), in an alpino environment, surrounded by rocky sheer sides where Peregrine falcon Falco peregrinus and Golden Eagle Aquila chrisaetos make their nests on the higher summits.

The reproduction of Little Owl in this unusual place was probably helped by the presence of wide pastures where this species could hunt insects and little birds without competiting with Tawny Owl which is very common here.

The picking of 28 pellets let us identify some preys hunted by Little Owl at high altitude. In addition to many insects (Coleoptera, particularly Lepidoptera) the remains of the following Vertebrata were found: Parus major, Phoenicurus ochruros, Fringilla coelebs, Carduelis carduelis,Turdus merula and Sorex minutus, Clethrionomys nivalis, Muscadinus avellinarius.

The second reproductive place, near Zogno and in a lower area, was located in a place which was not suitable to Little Owl.

In July, in Poscante , a Little Owl nestling was found wounded at 406 m. The most singular aspect is the place where nest was located: Little owl laid eggs in the roof gutter of an alpine hut, lonely and immersed in a forest dominated by Fagus (north exposure) near an hill-torrent with a great humidity.

These conditions are surely unsual for this species, however this nidification can have a reason because it is ot far from one of the most frequented migration pass, probably adopted by Little Owl to colonize Brembana Valley.

The valley, which is penetrable with difficulty by the main mouth, has many passes (usually located at 800 - 1000 mt.) which are used by Passeres for their migrations.

Little Owl probably uses these passes prefering a vertical ascent along the mountain sides, to avoid the difficulties to enter Val Brembana.

Some evening researches with play-back method during the reproductive period in 1998 and 1999 let us discover that in the first 12 km. of Brembana Valley there are no Little Owls.

On the contrary, near Zogno (which is next to the most important migration pass) we found the first territorial Little Owl. To confirm this thesis, in 1997, in Madonna del Perello, near Ornithological Station "La Passata" a Little Owl was captured in August (1000 mt.). Thanks to Maffeo Schiavi, director of the Station, I can list its data: weight 133,2 gm. , wing 15,8 mm., capture at 6.00 a.m. . in 13 August 1997.

Other discoveries confirm the impression that Little Owl prefers flying over the passes instead of entering the difficult mouth of Brembana Valley.

A Little Owl found tanks to play-back method on the rocky sides near Selvino (850 mt.) in a place between Val Seriana and Brembana Valley. Another Little Owl spontaneously singing was heard in the inhabitated place of Zambla Alta (pers. com. Guido Premuda) during summer 1998 at 1200 mt.

The presence of a forest in good state is favourable to Tawny Owl which is very common: a limiting element to Little Owl in some areas, even though the two species were both present next to the two reproductive places.

We can say that, globally, there is a population of 7-15 breeding-pairs in Val Brembana; except for the two nidifications, the species was found thanks to play-back method and a well defined environmental presence was verified. The two kinds of environment preferred by Little Owl were: suburbs of inhabitated places and, in two cases, pastures located at 400-500 mt., suoth and south-east exposures.

On 58 places where play-back method were used (Tab.1), I found five peranent places (at least three answers) and two where I got only one answer, but the low density can be explained by the characteristics of the alpino environment which is not suitable for Little Owl.

We should check if during winter Little Owls living in this region leave the area to go to spend the cold season on the plain, like Tawny Owls does.

Except for the nidification in Val Taleggio, the higher one discovered in Italy and far from the mouth of the valley, all other data are concentrated in the areas next to the most important migration pass, at about 1000 mt., in the territory of Zogno. These data and information witness the Little Owl colonization in a alpin valley, an unusual presece due to the good status of the species in Bergamo district and to the particular use of a migration way used by Passeres.

Table 1 Presence of Little Owl Athene noctua contact with Playback's method in Brembana Valley

Altitude of playback's station	n° stations	n° Little Owl	Emissions	Answeres
< 300 mt.	21	2	61	6
between 300 - 500 mt.	22	3	61	7
> 500 mt.	15	2	45	5

Andreotti in A.A.V.V.,1989 - Atlante degli uccelli nidificanti in Liguria Regione Liguria, Genova

Casini L. in Meschini E.,S.Frugis, 1993 - Atlante degli uccelli nidificanti in Italia Suppl. Ric. Biol.Selvaggina vol XX 1:344

Juillard M.,1985 - A propos des habitats de la Chouette chevéche Athene noctua dans les regions méditerranéennes Nos Oiseaux 38: 121-132

Juillard M.,H.Baudvin, J.Bonnet,J.C.Genot,G.Teysser, 1990 - Sur la nidification en altitude de la Chouette chevéche, Athene noctua, .Observations dans le Massif central (France) Nos Oiseaux 40:267 -276

Genot J.C.,1989 - Répartition et habitat de la Chouette chevéche (Athene noctua) dans cinq parcs naturels régionaux francais Aves- Actes:125 -132

Mastrorilli M., 1997 - Popolazioni di Civetta (Athene noctua) e selezioni dell'habitat in un'area di pianura della provincia di Bergamo Riv.Mus. Sc.Nat. E.Caffi 19: 15-19

Mastrorilli M.,1999 a - Caratteristiche dei ricoveri e dei siti riproduttivi di Civetta Athene noctua nelle province di Bergamo e Cremona Avocetta 23:163

Mastrorilli M.,1999 b - Rapaci pervenuti alla sede LIPU di Bergamo, dal 1990 al 1996, con particolare riguardo al periodo ed alle cause di ritrovamento Picus 25:35-39

Mostini L. in Mingozzi T.,G.Boano,C.Pulcher,1988 - Atlante degli uccelli nidificanti in Piemonte e Valle d'Aosta Monograf. VIII.Mus. region. Sc.Nat., Torino

Perugini F.,1991 - Avifauna della Val Taleggio (Provincia di Bergamo, Lombardia) Picus 17:61-82

Vogrin M., 1997 - Little Owl Athene noctua: a highly endangered species in NE Slovenia Buteo 9:99-102