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Acrocephalus 39  (178/179): 171–176, 2018
10.1515/acro-2018-0012
A contribution to the 
knowledge of diet composition 
of the Barn Owl Tyto alba in the 
area of Pisa (Italy)
Prispevek k poznavanju prehrane 
pegaste sove Tyto alba na območju pise 
(Italija)
(Birdlife International 2004). Its diet has 
been studied more extensively than that of any 
other bird of prey (Mikkola 1983, Everett 
et al. 1992, Taylor 1994, 2009, Bontzorlos 
et al. 2005, Leonardi & Dell'arte 2006). 
It mostly hunts small terrestrial mammals, 
mainly rodents (Mikkola 1983, Taylor 
1994), members of the three mammal families 
Soricidae (shrews), Cricetidae (voles) and 
Muridae (mice and rats) (Mikkola 1983, 
Brichetti & Fracasso 2006). Occasionally 
it preys on insects, amphibians, reptiles, birds 
(Mikkola 1983, Taylor 1994, Bontzorlos 
et al. 2005, Leonardi & Dell'arte 2006), 
fish and arthropods (Bontzorlos et al. 
2005). Its pellets are easy to find and small 
mammal bone parts are well preserved and easy 
to identify (Paspali et al. 2013). However, its 
hunting tactics remain controversial (Tores et 
al. 2005). Most researchers claim that the Barn 
Owl shows no food preferences and that the 
abundance of each species in the diet is a true 
reflection of prey abundance or accessibility in 
the field (Bunn et al. 1982, Tores et al. 2005, 
Yom-Tov & Wool 1997). On the other hand, 
some researchers suggest that it shows preference 
for small-sized prey and that its diet does not 
reflect the abundance of prey species in the field 
(Mikkola 1983, Tores et al. 2005, Yom-Tov 
& Wool 1997). These contrasting assumptions 
supposedly originate from different length of 
the studies (Tores et al. 2005). In his study, 
Contoli (1981) asserts that analysis of Barn Owl 
diet can provide information on the availability 
of small mammal prey species in a particular area, 
even when only few pellets are available (Bose 
& Guidali 2001). Mikkola (1983) suggests 
that the study of the Barn Owl's diet is suitable 
for determining the presence of nocturnal small 
mammal species within its hunting territory. On 
the other hand, some researchers have claimed 
that the Barn Owl is a selective predator, hunting 
its prey by preference (Yom-Tov & Wool 1997, 
Tores et al. 2005) and that its diet would not 
represent the true abundance of prey species in the 
field (Tores et al. 2005). 
Nevertheless, studies that compared pellet 
analyses with data from field trapping have also 
shown that prey size is an obvious limiting factor 
Tjaša Zagoršek1
1 Cankarjeva ulica 11, SI-3240 Šmarje pri Jelšah, 
e-mail: tzagorsek@gmail.com
Abstract
We examined the pellets of the Barn Owl Tyto 
alba, collected in Pisa, Italy, in 2012. Altogether, 
219 specimens of small mammals were found in 
85 pellets. The Barn Owl diet was composed of 
ten species of small mammals, representing three 
different families (Muridae, Cricetidae, Soricidae). 
The main prey species was the Wood Mouse 
Apodemus sylvaticus, followed by the House Mouse 
Mus musculus and the Savi’s Pine Vole Microtus 
savii. While the smallest of the small mammals 
from the area, the Etruscan Shrew Suncus etruscus, 
was well represented in the pellets, some larger 
species of small mammals were not represented at 
all. The reason for such result may lie in the upper 
limit for our Barn Owl’s prey size. Results suggest 
that optimal prey weight for our Barn Owl may 
be between 26–75 g of body mass, however, the 
prey can be occasionally as heavy as almost 100 g, 
represented by adult Rat Rattus spp. Nevertheless, 
our results may not reflect the true hunting strategy 
of the Barn Owl, but the availability of a certain 
food item at one point in time. 
1. Introduction
Barn Owl Tyto alba (Scopoli, 1769) is a 
widespread resident across much of Europe, which 
accounts for less than a quarter of its global range 
172
(Tores et al. 2005, Yom-Tov & Wool 1997). 
And for that, its diet may reflect not the true 
hunting strategy of a predator, but the availability 
of a certain food item at one point in time (Tores 
et al. 2005, Yom-Tov & Wool 1997). A selective 
predator is expected to consume a narrow range of 
prey species regardless of their abundance, while 
an opportunistic predator will take its prey in 
proportion to its abundance at any point in time 
(Tores et al. 2005, Yom-Tov & Wool 1997).
The Italian population of the Barn Owl is 
poorly known (Galeotti 2003). It appears to 
be declining in almost the entire Po Valley and in 
some central Italian areas of Mugello and province 
of Florence (0,03 pairs/km2) (Galeotti 2003). In 
Tuscany, its population is estimated at 500-1,500 
pairs, which are locally in decline (Brichetti & 
Fracasso 2006). 
The aim of our study was to: (1) present the 
diet of a local Barn Owl in Pisa (Italy); (2) examine 
whether its diet reflects species assemblage of the 
local fauna of small mammals in the community 
the owl preyed upon, and (3) to check if there is an 
upper limit in prey size.
This paper should be considered to contribute 
to the knowledge of the Tyto alba 's diet in Italy. 
2. Materials and methods
2.1. Study area
Pellets were collected in an abandoned house 
(43°39'38.2"N 10°17'55.9"E) near Marina di 
Pisa in Italy. Marina di Pisa lies on the left bank 
of the Arno River and is located directly north 
of Tirrenia and about 10  kilometres west from 
Pisa. The area is mostly cultivated with fields of 
corn and cereals, with coniferous woods nearby. 
The climate in this region is warm and temperate 
(Merkel 2018). Precipitation occurs mostly in 
winter, with relatively little rain in the summer. 
The average annual temperature is 14.8°C and 
the average annual rainfall is 877 mm (Merkel 
2018).
2.2. Methods
Pellets (n=85) were collected in July 2012 during 
a single visit of the nest site. We only collected 
pellets that were 4 – 5 days old (still damp and 
soft), 1 – 2 months old (dried out, black and shiny) 
or 2 – 4 months old (black colour slowly wears off, 
and they turn progressively grey). We determined 
the age of the pellets collected by following 
Chandler (2011). 
Their content was examined in the laboratory. 
Pellets were examined individually. To identify the 
skulls, teeth and other remains found in pellets, 
a stereo microscope with 20x magnification was 
used. We identified the remains to the species level 
by following Kryštufek (1985) and Aulagnier 
et al. (2009). The mean body mass of prey was taken 
from literature Aulagnier et al. (2009). Statistical 
analysis was conducted in the programme Past 
version 3.16 (Hammer et al. 2001). 
3. Results
We identified 219 individual mammal species from 85 
pellets. The owl's diet was composed of ten species of 
small mammals representing three different families, 
Muridae, Cricetidae and Soricidae (Table 1).
The main prey species of the Barn Owl was 
Wood Mouse (Apodemus sylvaticus) (34.7%). The 
second most important prey species in its diet was 
House Mouse (Mus musculus) (16.9%), followed by 
Figure 1: Study area near Marina di Pisa in Italy where 
the Barn Owl pellets were collected 
Slika 1: Obravnavano območje blizu kraja Marina di 
Pisa (Italija), kjer so bili nabrani izbljuvki pegaste sove
T. Zagoršek: A contribution to the knowledge of diet composition of the Barn Owl Tyto alba in the area of Pisa (Italy)
173
the Savi's Pine Vole (Microtus savii) (14.9%). The 
presence of Black Rat (Rattus rattus) and Brown 
Rat (Rattus norvegicus) was low (0.45 %).
The commonest prey weight in the investigated 
area was 11 – 30 g (Figure 2). Only in two cases was the 
prey heavier than 70 g, reaching a maximum of almost 
100 g. In both cases, the prey species was an adult Rat 
(Rattus rattus and Rattus norvegicus, respectively).
We tested if there were statistically significant 
differences between the proportions of prey species 
in different samples (Table 2). Only a single prey 
item in the pellet was present in 18.8% of all pellets 
collected. The observed proportion of all species 
found in the pellets contained a single prey item, 
and the proportion expected from the content of 
all pellets showed statistical differences between 
Table 1: Proportion of species identified from pellets of the Barn Owl (Tyto alba) found in an abandoned house near 
Marina di Pisa, Italy, in July 2012 (N=219) 
Tabela 1: Delež vrst, ki so bile identificirane iz izbljuvkov pegaste sove (Tyto alba), najdenih v zapuščeni hiši blizu 
Marina di Pisa (Italija) julija 2012 (N=219) 
Family Species Proportion (%) Number of prey (N)
Muridae
Wood Mouse (Apodemus sylvaticus) 34,7 76
House Mouse (Mus musculus) 16,9 37
Yellow-Necked Mouse (Apodemus flavicollis) 2,7 6
Black Rat (Rattus rattus) 0,45 1
Brown Rat (Rattus norvegicus) 0,45 1
Cricetidae
Savi's Pine Vole (Microtus savii) 14,9 33
European Water Vole (Arvicola terrestris) 9,6 21
Soricidae
Lesser White-Toothed Shrew (Crocidura suaveolens) 13,2 29
Etruscan Shrew (Suncus etruscus) 3,6 8
Bicolored Shrew (Crocidura leucodon) 3,2 7
Figure 2: The percentage of individual mass classes of prey in the diet of Barn Owl (Tyto alba) from the pellets found 
in an abandoned house near Marina di Pisa, Italy, in July 2012 (N=219) 
Slika 2: Odstotek posameznih masnih razredov plena v prehrani pegaste sove (Tyto alba), ki so bili najdeni v 
izbljuvkih, nabranih v zapuščeni hiši blizu kraja Marina di Pisa (Italija) julija 2012 (N=219)
Acrocephalus 39  (178/179): 171–176, 2018
174
samples. The comparison of two samples, first 
representing the whole sample and other containing 
only one item, showed statistically significant 
differences indicating that the hunting strategy of 
our Barn Owl is not opportunistic. 
4. Discussion
Small mammals were the most important 
prey in the Barn Owl's diet in the area of Marina 
di Pisa, Italy. The most preyed species was the 
Wood Mouse, which is consistent with the articles 
of other authors (Lovari et al. 1976, Lovari 
1974, Mikkola 1983, Obuch & Benda 2009, 
Chandler 2011). Small presence (2.7%) of the 
Yellow-necked Mouse in the diet may be due to 
the fact that habitat suitable for this species is very 
rare within the hunting area of the Barn Owl. 
The important species in the diet was also Lesser 
White-toothed Shrew with the frequency of 13.2%, 
while its congeneric species, the Bicoloured White-
toothed Shrew, was four times less common. The 
Etruscan Shrew is making a very small contribution 
to our Barn Owl diet. This may be due to the fact 
that species is very small in size and has a low 
biomass. The presence of Black Rat and Brown Rat 
was low, and its presence can be explained by a farm 
and farmland in the study area. 
In his study of the Barn Owl diet, Taylor 
(1994) analyzed pellets from the different 
European countries. He assumed that one pellet 
per day is produced by an owl, and came up with a 
figure of about 75g of food per day needed for the 
adult Barn Owl. This indicates that prey body mass 
is a limiting factor. This may be due to the fact that 
for any predator, and particularly a flying one, there 
may be an upper limit for prey size which can be 
captured and carried away (Taylor 1994). The 
results from our analysis of the pellets indicate that 
our Barn Owl does not prey opportunistically. The 
Table 2: Chi-square test of expected and observed percentage of small mammals where one prey item was present 
in a pellet (N=16)
Tabela 2: Hi-kvadrat test med pričakovanimi in opazovanimi odstotki malih sesalcev, kjer je bil v izbljuvku najdena 
vsaj ena enota plena (N=16) 
Species Expected Observed P
Apodemus sylvaticus 34.7 43.8 N.S.
Mus musculus 16.9 0 < 0.001
Microtus savii 15.1 12.5 N.S.
Crocidura suaveolens 13.2 6.3 N.S.
Arvicola terrestris 9.6 37.5 < 0.001
Suncus etruscus 3.7 0 N.S.
Crocidura leucodon 3.2 0 N.S.
Apodemus flavicollis 2.7 0 N.S.
Rattus rattus 0.5 0 N.S.
Rattus norvegicus 0.5 0 N.S.
χ² – test = 47.7 < 0.001
T. Zagoršek: A contribution to the knowledge of diet composition of the Barn Owl Tyto alba in the area of Pisa (Italy)
175
commonest prey weight in the investigated area was 
11 – 30 g. Only in two cases was the prey heavier 
than 70 g, reaching a maximum of almost 100 g. In 
both cases, the prey species was an adult Rat (Rattus 
rattus and Rattus norvegicus, respectively). Numbers 
of prey individuals of small mammals in our pellets 
are showing that by increasing the number of prey 
items within a single pellet the relative abundance 
of large species  – in this case, the heaviest of the 
five most commonly preyed species is Arvicola 
terrestris – decreases, whereas on the other hand the 
smallest species Suncus etruscus was only detected 
in pellets with four and five prey items and never 
less. Our results suggest that pellet contents do not 
reflect the relative abundance of small mammals in 
the area, but it can be used as a complementary tool 
to supplement the faunal lists of small mammals 
in a given area. This study also indicates that Barn 
Owl may not be an opportunistic predator as the 
proportion of small mammals in different samples 
of pellets greatly differs and an obvious upper limit 
in prey body size exists for our Barn Owl. 
Acknowledgements
I am grateful to Katarina Denac and Urša Koce for 
their valuable comments and suggestions on the 
draft. A very special thank you goes to Dr Gianluca 
Bedini from  Centro Recupero Uccelli Marini 
e Acquatici di  Livorno with his help during the 
fieldwork. 
Povzetek
Preučili smo izbljuvke pegaste sove Tyto alba, 
zbrane v okolici Pise (Italija) leta 2012. Skupno smo 
našli 219 osebkov malih sesalcev v 85 izbljuvkih. 
Prehrano pegaste sove je sestavljalo 10 vrst malih 
sesalcev iz treh družin (Muridae, Cricetidae, 
Soricidae). Glavna vrsta v prehrani je bila gozdna 
miš Apodemus sylvaticus, sledita ji hišna miš Mus 
musculus in Savijeva kratkouha voluharica Microtus 
savii. Najmanjša vrsta z območja, etruščanska rovka 
Suncus etruscus, je bila dobro zastopana v izbljuvkih, 
medtem ko nekaterih večjih vrst nismo ugotovili, 
kar morda odseva zgornjo mejo velikosti za plen 
pegaste sove. Zdi se, da je optimalna teža plena med 
26 in 75 g, občasno pa upleni tudi osebke, ki tehtajo 
do 100 g, npr. odrasle podgane Rattus spp. Kljub 
vsemu se moramo zavedati, da naši rezultati kažejo 
na razpoložljivost plena v določenem časovnem 
obdobju, ne pa nujno prehranske strategije pegaste 
sove.
Key words: Barn Owl, Tyto alba, diet, small 
mammals, Pisa, Italy
Ključne besede: Pegasta sova, Tyto alba, prehrana, 
mali sesalci, Pisa, Italija
5. References
Aulagnier S., Haffner P., Mitchell-Jones, A. J., 
Moutou F., Zima J. (2009): Mammals of Europe 
North Africa and the Middle East.  –A&B Black 
London. 
Birdlife International (2004): Birds in Europe: 
population estimates trends and conservation 
status. – BirdLife International Cambridge. 
Brichetti P. Fracasso G. (2006): Ornitologia 
Italiana Vol.3 Stercorariidae-Caprimulgidae.  – 
Alberto Perdisa Editore Bologna. 
Bontzorlos V. Peris S. Vlachos G. C. 
Bakaloudis D. (2005): The diet of Barn Owl in 
the agricultural landscapes of central Greece. – Folia 
Zoologica. 54 (1/2): 99–110.
Bose M. Guidali F. (2001): Seasonal and geographic 
differences in the diet of the Barn Owl in an agro-
ecosystem in northern Italy.  – Journal of Raptor 
Research 35 (3): 240–246. 
Bunn D.S. Warburton A.B. Wilson R.D.S. (1982): 
The Barn Owl. – Poyser Calton. 
Chandler D. (2011): Barn Owl. Firefly Books. – New 
Holland Publishers (UK) Ltd. 
Contoli L. (1981): Ruolo dei Micromammiferi nella 
nicchia trofica del barbagianni (Tyto alba) nell'Italia 
Gentro Meridionale. – Avocetta 5: 49–64.
Everett M. Prestt I. Wgagestaffe R. (1992): Barn 
and bay owls. Owls of the World: Their Evolution 
Structure and Ecology – Peter Lowe London.
Galeotti P. (2003): Barbagianni. In: Uccelli d'Italia. 
(a cura di: Spagnesi M. Serra L.). Quad. Cons. Natura 
16 Min. Ambiente – Ist. Naz. Fauna Selvatica: 202–
204. 
Hammer O. Harper D.A.T. Ryan P.D. (2001): 
Past: Paleontological Statistics software package 
for education and data analysis.  – Palaeontologia 
Electronica 4(1).
Kryštufek B. (1985): Naša rodna zemlja. 4 Mali sesalci 
(Mladinska raziskovalna akcija "Okolje v Sloveniji" 
III Raziskovanje tal).  – Prirodoslovno društvo 
Slovenije Ljubljana. 
Acrocephalus 39  (178/179): 171–176, 2018
176
Leonardi G. Dell’arte G. (2006): Food habits of the 
Barn Owl ( Tyto alba) in a steppe area of Tunisia. – 
Journal of Arid Environments 65: 677–681.
Lovari S. (1974): The feeding habits of four raptors in 
central Italy. – Raptor Research 8: 61–63. 
Lovari S., Renzoni A., Fondi R. (1976): The 
Predatory Habits of the Barn Owl (Tyto Alba 
Scopoli) in Relation to the Vegetation Cover.  – 
Italian Journal of Zoology 43: 173–191. 
Merkel A. (2018): Climate data – climate: Marina di 
Pisa. Accessible online: https://en.climate-data.org/
location/710944/ 
Mikkola H. (1983): Owls of Europe.  – T. & AD 
Poyser, London. 
Obuch J., Benda P. (2009): Food of the Barn Owl 
(Tyto alba) in the Eastern Mediterranean.  – Slovak 
Raptor Journal 3: 41–50. 
Paspali G., Oruci S., Koni M., Wilson I. F., 
Krystufek B., Bego F. (2013): Seasonal variation 
of small mammals in the diet of the barn owl (Tyto 
alba) in the Drinos River valley southern Albania. – 
Turkish Journal of Zoology 37: 97–105.
Taylor I. (1994): Barn owls: Predator-prey relationship 
and conservation.  – Cambridge University press, 
Cambridge. 
Taylor I. R. (2009): How owls select their prey: a study 
of Barn Owls Tyto alba and their small mammal 
prey. – Ardea: 97(4): 635–644.
Tores M., Motro Y., Motro U., Yoram Y.T. (2005): 
The Barn Owl – a selective opportunist predator. – 
Israel Journal of Zoology 51: 349–360. 
Yom-Tov Y., Wool D. (1997): Do the contents of 
Barn Owl (Tyto alba) pellets accurately represent the 
proportion of prey species in the field? – Condor 99: 
972–976. 
Prispelo / Arrived: 12. 11. 2018
Sprejeto / Accepted: 29. 12. 2018
T. Zagoršek: A contribution to the knowledge of diet composition of the Barn Owl Tyto alba in the area of Pisa (Italy)